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    1. #1
      Member theshadow27's Avatar
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      Headlight PWM details?

      SwedeSpeed P1 (C30, S40, V50, C70) HID Retrofit Index
      1. SKBOWE Plug-and-Play harness for P1 HID conversion
      2. Background info, general questions, and share your HID setup
      3. KBOWE How-To (Original 2009 Version) build your own PWM filter
      4. Original 2009 investigation and technical discussion on S40 HID issues (you are here)
      5. ForceFed’s E46 D2S Bi-Xenon Projector Retrofit guide
      6. Rewire OEM Bi-Xenon headlights to work on the halogen harness
      7. DRL Disable Alone not enough for safe Aftermarket HID retrofits
      8. LizardOfBodom's EU/RHD Bosch ("E46") Bi-Xenon replica retrofitting writeup + angle eyes + running lights



      PLEASE do not revive this 2009 thread

      This thread contains the original (c. 2009) investigation into the issues with P1 HID low-beam conversions. The Edited OP (c. 2011 - the real OOP was moved to post#2) was an older attempt to consolidate HID related info, and is included in the quote below only for posterity. If you are looking for the most accurate technical information on P1 HID retrofit issues, see the general HID discussion thread or https://www.skbowe.com/a/issues. Thanks!




      Quote Originally Posted by theshadow27

      This post has information accumulated from a variety of sources including the statistics thread (here and on C30 World), and a variety of HID related threads (1, 2, 3, 4, etc...).

      Section 1 - Symptoms and Problem with P1 (S40 2004.5+, V50, C30, and C70 2007+) HID conversions
      Some of the common problems that arise with an HID conversion include:
      • Faliure to start - one or both bulbs
      • Flickering during operation
      • Dim output or excessive warmup time
      • Bulb Out Warning (BOW) message on the dash board LCD screen (DIM)
      • Windshield Wiper (WMM) failure

      Any or all of these conditions can occur when attempting to install an HID kit in one of the applicable cars.

      Section 2 - Cause of the Problems with HID retrofits
      All of these problems come from one source. The computer module that controls the headlights, the Central Electronic Module (CEM) applies a pulse-width modulated (PWM) regulated voltage to the low beam halogen lamps to keep the voltage they see at 13.0V. It was designed to do this because halogen bulbs will last longer at 13V than the 13.5V or 14V at which the electrical system runs. Since the low beam bulbs are also the Daytime Running Lights (DRL) and are on all the time, Volvo wanted to maximize the life of the bulb. For halogen bulbs this is actually a good thing, and it does what it is supposed to.

      The PWM works as follows: A halogen bulb is, in practice, a simple resistor. As such, the voltage across it is directly proportional to the current through it. By switching current on and off several times per second (about 80, actually), the CEM can control the average voltage across the bulb and thus keep it at 13.0V. The switching is not bad for the bulb, and the pulses are short enough (about 4/100th's of a second) that the human eye can't tell it's not a constant illumination.

      We run into problems during an HID retrofit because of the HID ballast. What does the ballast do? An HID is an arc lamp which means there is no filament, but instead two contacts within a quartz envelope filled with xenon gas. Xenon is normally an insulator, meaning that it does not conduct electricity, but at a high enough voltage (between 800V and 2kV) the gas will ionize (just like a bolt of lightning), allowing electricity to flow between the contacts much more easily. We call this "lighting" or "igniting" the bulb. So the first job of the ballast is to ignite the arc.

      If this high voltage was not removed, so much current would flow that the the contacts would melt and the capsule would shatter! So the second job of the ballast is to reduce the voltage to a more manageable level. HID bulbs are rated for a specific current (normally around 300mA) that they can operate at without damage. The ballast reduces the voltage to whatever level is required to keep this constant current flowing through the bulb.

      When power is first applied to the ballast, it uses an inductor (in much the same way as the ignition coil sparks the spark plugs) to create the starting voltage across the bulb. Then, it gradually reduces the voltage until the constant current condition is met. To do this it uses a switch-mode power supply (SMPS) which is controlled by analog or digital feedback (this is where the "digital" in "digital ballast" comes from), that switches around 100KHz, or more. By measuring the current, it can switch on for longer or shorter to create the required average. This startup process takes about 3 seconds in most ballasts, although older ballasts can take much longer (30 seconds or more).

      So there's a major problem when an HID ballast is hooked to the 80Hz PWM of the CEM. Every time the CEM switches the output on, the ballast begins it's startup procedure. When it shuts off, the ballast looses power.

      Depending on the construction of the ballast and the duty cycle of the PWM (which depends on a number of factors, primarily battery voltage) the ballast might repeatedly try to start the bulb. Each time this happens, there is a large inductive flyback on the headlight ground - if you've ever touched the ground terminal on an old-fassion ignition coil while the car was running you know first hand - essentially a negative high voltage pulse. Normally this pulse would just go to ground, but it just so happens that the wiper motor (WMM) shares a ground wire with the headlights. Since there is an inherent resistance in the wire-chassies-battery connections, repetitive high voltage spikes can show up in the WWM and have caused many failures of a particularly sensitive component inside. This is the cause of symptom #4.

      Other ballasts have a "warm start" condition in which they can tolerate short breaks in input power and continue operating so long as the gas remains ionized (about a second or so). These ballasts may work intermittently, again depending on the duty cycle of the PWM. This may seem OK, except that there is a filter circuit inside of the ballast required for proper operation of the SMPS. This circuit consists of an inductor and a capacitor, set up to "cover" the high-current spikes produced by switching, and allowing the ballast to draw a relatively steady current once running (see graphs). The filter is designed to deal with the operating frequency of the ballast, which is 10,000 times faster (or more) than the the PWM frequency of the CEM. In effect, subjecting it to low frequency modulation causes a large AC current to flow through the capacitor in the filter, several times more than it was designed for. This causes excessive heating and premature failure. The various stages of this degradation will cause the other symptoms listed above.

      In all cases, when the ballast is no longer able to maintain the arc within the HID capsule, the capsule acts as an insulator, preventing current from flowing. This reduces the current that the ballast draws, which trips the BOW warning in the car.

      Section 3 - How to fix the problem

      There are three ways to get around these problems:
      • DRL disable does NOT disable PWM (just the DRL 1/2 brightness)Disable the PWM modulation. This can be done by having a dealership flash the car to disable DRLs. This is the best option if DRLs are not a legal requirement where you live, and you don't mind the $80 for the dealer to do the flash.
      • Bypass the CEM all together by using a battery harness with a relay. This gives the HID ballasts a constant DC voltage, since the relay stays switched on regardless of PWM modulation. The downside to this is that the relay does not draw as much current as the halogen bulb did, and the "bulb out warning" message will continue to be displayed.
      • Smooth the PWM modulation to approximate a DC voltage at the ballast. This is the cheapest solution that doesn't cause an error message, but because of the low frequency (80Hz) and large current (3A+), an extremely large (22,000uF or more) capacitor must be used. See here.


      The third option is what developed from this thread (and the others). Essentially we designed a "bulb out warning eliminator" (BOWE) of which the first was built for SwedeSpeed member Kyle (ForceFed Motorsports), which for lack of better nomenclature became known a "KBOWE". The KBOWE consists of a large bypass capacitor and a diode, situated between the CEM and the HID ballast.

      The capacitor serves to smooth the PWM voltage by shunting the AC components to ground. It's specification isn't supercritical, but it must have a ripple rating of at least 5A, which generally precludes sizes smaller than 22,000uF, and a voltage rating of at least 16V, but 25V or even 35V provide a better safety factor. Several smaller capacitors can be used in parallel if a larger unit is not available, provided they are all rated at least 16V.

      The diode is situated to prevent current from flowing back to the CEM from the capacitor when the PWM switch is "off". While the exact mechanism is not known, empirical data suggests much better performance with the diode than without, and in some cases omitting the diode prevented the circuit from working at all. This is probably due to the current measurement mechanism within the CEM. The diode specification, again, is not critical, but it must be rated to at least 5A (10A or 15A provides a better MOS) and 16V or higher reverse voltage. A low forward voltage is also desirable, so most KBOWEs have employed Shottkey rectifying diodes.

      The ground terminal of the headlight, CEM, and capacitor are all tied together and then directly to the chassis at the location of the KBOWE. Both the capacitor (which can absorb negative transients) and the grounding combine to eliminate the possibility of damage to the WMM.

      One of these diode-capacitor assemblies is required per ballast. The most straightforward approach is to combine two assemblies in one box and tap it into the wires where they come out of the connector. This allows both capacitors to share a ground connection. Such an assembly is described in detail in this tutorial. Another approach with a slightly higher cost would be to create two identical units, hooking up between the vehicle wiring and the ballast at the headlight assembly, and grounding each independently.

      The KBOWE has been extensively tested with over ten vehicle-years of operation since 2009 (as of 2011). The KBOWE is designed specifically for the challenges inherent to the P1 cars and, at the time this article was written, the only "adapter" type design that provides both HID functionality and WMM protection.

      Section 4 - How not to fix the problem

      A number of "solutions" have been proposed to allow retrofits to function normally. The majority users end up purchasing what have been called "BOW eliminators", "error cancelers", "harnesses", ect... They typically consist of a small box with two connectors, one male which plugs into the HID ballast, and one female which plugs into the power supply wires. For the sake of notation, we will call this class of solution the BOW-3, which is the model number of the product produced by DDM tuning.

      The BOW-3 is essentially a beefed-up version of the filter inside of the HID. It contains another inductor and capacitor, to reduce the small 100KHz ripple imposed on a DC supply voltage. It works well with cars that (1) supply a DC voltage, and (2) are confused by this ripple.

      The capacitor in the BOW-3 filter is about four times bigger than the capacitor in the ballast, and it has a correspondingly greater ripple (AC) current rating. However it's nowhere near big enough to deal with 80Hz PWM - and even if using a BOW-3 initially allowed an HID retrofit to work acceptably, most fail within a year or two because of this ripple current. About 75% of BOW-3 units work the first time, of those 65% fail within one year (sample size = 18 installs) and 20% take the WMM out when they fail. If you have a BOW-3 and it is still working, consider yourself on borrowed time.

      Section 5 - Random Comments

      Some users (6 of 44 recorded) have reported kits to function "perfectly" without any adapter, relay harness, or software flash. The majority of these users have "Kaixen" kits obtained from a group buy. Since I have not found an active group buy and the company does not seem to have a functional website, I can't obtain a kit for more rigorous evaluation. The Kaixen kits from various group buys (not just Volvo forums) have different styles of ballast, and each ballast style may have different components within them.

      While there is no evidence to the contrary, I believe that (1) these kits are not designed to work with PWM supply voltage, and (2) that operating outside of design requirements will cause undesirable effects. Until I get my hands on a Kaixen kit I can't provide more information, but I do not recommend running any HID kit without one of the corrective measures listed above.

      Jacob
      Last edited by theshadow27; 11-18-2017 at 08:50 PM.
      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    3. #2
      Member theshadow27's Avatar
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      I have a set of hid50 50 watt HIDs on the way for my '05 T5, but before I think about hooking it up I'd like to know some more about the PWM circuitry in the CEM. I have been looking through the HID threads on here for 72 hours, and there's a lot about which different brands work with and without harnesses, dummy loads, frying the CEM, etc... but nothing about why they work or fry.

      According to the wiring diagram, pins E:25 and E:37 on the CEM (4/56) go directly into the logic, and are denoted by a JFET symbol which I assume means that they are highside switched. According to the electrical spec (page 20), the headlights are regulated to 13.0 volts + 0.2 volts via PWM:

      And the CEM monitors lamp faults.

      To me (without seeing the guts of the CEM) this means that inside there is:
      1) A voltage monitoring feedback loop comparing output voltage with a fixed voltage source hooked a PWM modulator to maintain 13.0 volts.
      2) A current shunt, probably a low value (<0.1 ohm) 5 or 10 watt resistor, with another comparator checking for current flow.

      Further, based on the nature of halogen lights:
      3) There is no ripple reduction (inductors, capacitors, etc...) in the outputs because filaments don't care.
      4) There is no reverse protection because there are no (significant) inductive components in a halogen bulb.

      On to the questions. Assuming the above is accurate (if it's not, please chime in!) then the things that could affect functionality are:
      A) HF/RF artifacts from low-quality ballasts may produce reverse current spikes in the line, and the JFET is not protected against such.
      B) The large initial current from the ignition pulse is not what the current shunt pickup is looking for (bulbs ramp up linearly, their resistance decreases as they warm up, and current increases as resistance decreases, until they reach equilibrium). This could, if the monitoring circuit was fast enough (< 200ms sample time, w/ poor ripple isolation maybe longer) be perceived as a short, and cause a shutdown/bulb malfunction indication.
      C) The stock halogen wiring is undersized for the current inrush (looks to be about 16ga, no?) and the 10-15 amp current in addition to the the 0.5-1.0volt drop between the CEM voltage meter and the HID will cause line voltage at the ballast to fall below it's low voltage cutoff, and prevent said ballast from sustaining an arc.
      D) The ballasts may not like unfiltered PWM, and lower quality units without additional filtering/isolation could blow up pretty quick.

      The reason I'd like to know this stuff is so I can design a circuit to counter any ill effects before I have to replace my CEM. There's three strategies that I can think of:
      I) Add a schottky diode in series with the halogen bulb output on the CEM, and a second schottky reverse-biased between the anode of the first and ground. On the anode side, add a few mil-spec high-temp 10,000 uF caps as filters. Then hook this filtered output to the HID. This assumes the capacitors could store enough charge before the ballast's under-voltage cutoff was exceeded to sustain the ignition current. In any case, it wouldn't hurt anything, the question is if it would help. Total cost: ~$4 / side
      II) Add a tuned inductor in series with the halogen bulb output on the CEM, picking a value based on the PWM frequency. This should take out most of the ripple, but the circuit described in (I) would most likely also be required after the inductor. Total cost: ~$6 / side
      III) If that is insufficient, the madness starts. Assuming that the CEM is totally and utterly incapable of providing the required current safely, we need to devise a system that guarantees the CEM sees 4.23 amps at all times. This would require intercepting the output from the CEM and isolating it with a diode. A P-type MOSFET connected to a +30 terminal after the diode would provide additional current if draw CEM draw exceeded 4.23 amps at any point. A N-type MOSFET, with the source connected at the P-type drain, and the drain connected to a 15-30 watt 1 ohm shunt hooked to ground, would be used if the current fell under 4.23 amps. All of this would need a +0.1% 0.1 ohm shunt resistor in series with the whole ordeal. Said shunt would drive a pair of comparators, or even a MCU with dual ADC's, to determine what FET was active at any given point. This circuit would also need an inductor before, and capacitors after. Like I said, worse case, but guaranteed to not damage anything ever. Total cost: ~$35 / side.

      Any thoughts from folks that have tried HID conversions? I'm not looking for "Oh, kit blah-blah-blah works fine", because that doesn't help answer the question. Much more useful would be what didn't work at first, and how you fixed it. Or if something broke, how and why. For the Volvo geniuses out there, any flaws in my logic? Electronic nuts - am I missing something?

      Thanks much, I love this car, and would rather run halogens than risk messing up the CEM. If I can't figure this out, I'm seriously considering getting the other engine harness and buying the OEM bi-xenons ($2K+ labor )... Cheers, JSD


      Modified by theshadow27 at 6:48 PM 11-11-2009

      Here's (rough) schematics for circuits I, II, and III
      http://theeshadow.com/files/volvo/hidcircuits.pdf

      Last edited by theshadow27; 10-11-2011 at 12:42 PM. Reason: fixed broken links/pics
      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    4. #3
      Member theshadow27's Avatar
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      Re: (theshadow27)

      Measured 82 hz, 12.02 volts at the bulb. I'm very suspicious of that measurement... PWM (for LEDs anyway) is normally in the 100-300khz range.

      If that's the real measurement, there isn't a big enough coil available to do solution II practically. That leaves I and III.

      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    6. #4
      Member jdsr917's Avatar
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      Re: (theshadow27)

      What LOL i do not understand not one thing on this page
      S40 T5

    7. #5
      Member theshadow27's Avatar
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      Re: (jdsr917)

      Sorry, that's probably a bit hard-core for most non-Electrical-engineering folk Here's the cheat sheet:

      HID = High Intensity Discharge, a kind of lamp that uses an arc to create light instead of a filament. See wiki.

      HID Ballast = the box which supplies the necessary high voltage(s) and control current within the HID lamp (see wiki.

      PWM = Pulse Width Modulation, a form of digital control used commonly by microprocessors to regulate voltage. See wiki.

      CEM = Central Electronic Module, the brains in the S40. Basically a duel core computer.

      Dummy load = another name for a resistor that simulates a 55 watt headlamp bulb to trick the CEM into thinking one is connected. Converts 55 watts to heat.

      Pins E:25, E37 = the CEM pins that go to the left/right headlights in the S40. The diagram is taken from the wiring diagram.

      Lamp Fault = "bulb burnt out" indicator message. Triggered when the computer sees something wrong with the headlight outputs.

      JFET = A type of transistor that can be used for PWM. See wiki. Sensitive to reverse current fluctuations and ESD.

      Fixed Voltage Source = A special electronic component consisting of a fixed current source (see wiki and a current-to-voltage converter (see wiki that can be used to regulate voltage by comparing it's generated voltage to the measured voltage.

      Current shunt = A low value resistor inserted in a circuit to measure current flow. DC current cannot be directly measured, but rather we measure the voltage drop across the shunt and extrapolate current via ohms law (see wiki). Also see wiki.

      Halogen light = The standard type of headlight that uses a bulb with a filament. See wiki.

      Current ripple = A byproduct of PWM control (see the PWM wiki) where voltage drops between "on" modulations. See wiki. Can cause problems on electronics which expect clean DC voltage.

      Reverse bias = A state where the voltage on the negative (ground) rail has greater potential than the voltage on the positive (12v+) rail. This can occur during an inductive flyback cycle (see wiki) that the HID ballast uses to step 12 volts up to 20,000v or higher.

      HF/RF = High Frequency and Radio Frequency noise, AC currents that ride over the DC power wires running between the headlights and the CEM, caused by the ballast flyback cycle.

      Monitoring time = The CEM (or any computer for that matter) can't monitor values all the time. Instead, it uses an A/D (analog-digital) converter (see wiki) to measure values every so often. The longer the monitoring time, the less chance it has a picking up the current spike created when the HID ignites the arc.

      Voltage drop = Although they are conductors, wires have resistance, and longer wires have more resistance. High current flow through small wires will drop the voltage measured at each end, sometimes significantly. This is why battery cables are thicker than audio cables, for example. See wiki

      Blow up = In point D. I mention blowing up. This is caused by resonant feedback (like audio feedback, wiki between the oscillator driving the CEM PWM circuit and the oscillator driving the ballast transformer circuit. This will create alternating high and low current spikes which easily exceed component ratings and cause said components to explode.

      Filtering = Various electronic circuits designed to reduce current ripple.

      Schottky = A type of diode (see wiki) that has a low forward voltage, and a high current capacity. See wiki. A diode lets current flow only one way.

      Series = A particular configuration of electronic components within a circuit. See wiki.

      Capacitor = An electronic component which stores electrical current, and can release it rapidly. See wiki. Capacitors are commonly used to reduce ripple.

      Tuned inductor = An inductor is an electronic component commonly known as a coil. It also stores electrical current, but in a different way as a capacitor. See wiki. They can be used to filter a specific frequency of ripple very effectively, selecting the correct inductance value for a particular frequency is called tuning.

      The part III is basically saying "Use the CEM to power the light, BUT if the ballast wants to take more current than it's expecting, instead connect straight to battery, OR if the ballast wants to draw less current than it's expecting, hook up a resistor as a shunt". This will trick the CEM into thinking there's a bulb connected, but not waste 55 watts as heat.

      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    8. #6
      Junior Member I Saw 50's Avatar
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      Oh jeez that is some in depth stuff! Way beyond my curse at electricity when it shocks me knowledge. But judging from that, and not to side track you or anything, but would that be able to be done backwards?

      For vehicles already with the HID lights except for the ones with the DRL's removed they are constantly on. Would some sort of relay be able to shut the lights off and on based on the photocell on the dash and the car's day/night scheme?

      Just thinking, don't really know the inner workings of the modules.

      Car, Passenger, 1ea

    9. #7
      Member theshadow27's Avatar
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      Re: (I Saw 50)

      Unfortunately no. The factory Bi-Xenon system is significantly more complicated (hard to believe, but it is) than the halogen system, so much so that it requires a completely different engine harness. In the stock Bi-Xenon system, the CEM is connected to the headlights by a single wire over the (EDIT:GDLs run off LIN direct from the CEM) LIN bus (low speed in-car network). This wire sends the "GDL Master" module (passenger side headlight computer) the signal to turn off/on and low/high beam. The "GDL Master" module relays this information to the "GDL Slave" (driver side headlight computer) over another wire using the LIN protocol.

      So basically the signals for the factory Bi-Xenons are all computer codes over the car's network. The day/night sensor a photodiode connected directly to the CEM, so intercepting it would be difficult. Even with that sensor though, the most you could do is cut all power to the GDL modules. This would, with overwhelming probability, cause a warning code to be stored and a check engine light. The CEM isn't very fond about loosing modules.

      I guess it'd be easier to take it into the dealership. No easy outs for less than the $70 or whatever they charge. Won't start this here, but I'd personally never take out the DRLs, especially in Xenon, they look so f-ing cool.


      Modified by theshadow27 at 7:09 PM 9-9-2009


      Modified by theshadow27 at 7:09 PM 9-9-2009

      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    10. #8
      Junior Member I Saw 50's Avatar
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      Aaand my eyes almost went cross eyed. But that's some real good info. Shame there's no real workaround except for the dealer. I've already had two bulbs go out on mine.
      Car, Passenger, 1ea

    11. #9
      Member theshadow27's Avatar
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      Re: (I Saw 50)

      For what it's worth, here are the schematics for the two systems:
      Halogen: http://theeshadow.com/files/volvo/3978202_58.pdf
      Bi-Xenon: http://theeshadow.com/files/volvo/3978202_59.pdf
      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    12. #10
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      Re: (theshadow27)

      Kudos for breaking this down but i feel at this point you might as well just buy a car with factory Bi-xenons before taking the time to rewire the car for them.

      Ive never looked that in depth as to why the failures are occuring but your facts are pretty solid.

      Has there actually been a recorded CEM failure due to HID's, i had only heard of the WMM?

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    13. #11
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      Re: (ForceFed Motorsports)

      The WMM? The Wiper Motor Module?

      I have a 2005 T5 AWD with the M66 and sport package. This is my second (2005 T5 AWD M66), the first was totaled in an accident this spring. The problem is, when I went to find another T5 AWD with M66, there were 2 on the east coast. Volvo apparently only made 6 speed AWDs from 2005-2007, before they figured that anyone with enough cash to buy an AWD didn't want a MT. Now they don't sell any (T5, T5 AWD, or 2.4i) 6 speeds in the US

      Trust me, if I could go down to the dealer and pick up a '09 or '10 T5 AWD in 6 speed manual and Bi-Xenons, I'd do it in a heartbeat. But I can't, so I'm stuck with this one.

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    14. #12
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      Re: (theshadow27)

      Quote, originally posted by theshadow27 »
      Measured 82 hz, 12.02 volts at the bulb. I'm very suspicious of that measurement... PWM (for LEDs anyway) is normally in the 100-300khz range.

      If that's the real measurement, there isn't a big enough coil available to do solution II practically. That leaves I and III.

      Wiki link says 100 to 120 Hz? Not sure if the PWM requency differs from car to car, could be the reason why some cars are able to fix the HIDs directly, while others needed the DRLs disabled.

      Heck, I'm an Electrical Engineer and I only understand half of your post. Not even sure if my low end (free) multimeter even measures frequency.

      Quote, originally posted by theshadow27 »
      C) The stock halogen wiring is undersized for the current inrush (looks to be about 16ga, no?) and the 10-15 amp current in addition to the the 0.5-1.0volt drop between the CEM voltage meter and the HID will cause line voltage at the ballast to fall below it's low voltage cutoff, and prevent said ballast from sustaining an arc.

      From my limited EE knowledge, a 55W HID bulb should only take as much, if not less, current as a standard 55W bulb? The BOW harness simply makes up for the differences in the current (ie additional large resistor in parallel) between a 55W HID and the stock halogen so that the CEM thinks the bulb is not faulty. I have not checked the voltage / current that much to know the variations, but a 55W HID on a line rated for 55W at the same voltage, should be able to handle the currents involved.

      I would vote for solution I, but won't be able to use it on my setup as I'm using a battery harness, aka relay switch.

      Quote »
      II) Add a tuned inductor in series with the halogen bulb output on the CEM, picking a value based on the PWM frequency. This should take out most of the ripple, but the circuit described in (I) would most likely also be required after the inductor. Total cost: ~$6 / side

      Shouldn't a capacitor do the trick? I'm not too familiar with inductor. ie smooth out the ripple effect of the PWM?


      Modified by fone at 8:50 PM 9-9-2009

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    15. #13
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      Re: (fone)

      Quote, originally posted by fone »

      Wiki link says 100 to 120 Hz? Not sure if the PWM requency differs from car to car, could be the reason why some cars are able to fix the HIDs directly, while others needed the DRLs disabled.

      Different PWM frequencies are used for different applications. For example, DC-DC converters work at ~100khz (100,000 cycles/second) and fuel injectors PWM has to be at least 20khz if not higher, to keep up with intake valve operation. Lower frequencies are suitable for incandescent lights, since the human eye can only pick up frequencies lower than ~30hz.

      In any case however, the frequency is fixed by the MCU's clock, which is driven by a crystal oscillator. Unless they change the speed of the CEM processor (not likely during a production run) the PWM frequencies will be the same.

      I doubt the PWM frequency has anything to do with using the stock harness for HIDs vs disabling DRLs. Even with DRLs disabled, the low beam is still PWM modulated (when on). I suspect it has more to do with the HID kit, and said kit's ability to handle transient voltages.

      Quote, originally posted by fone »

      From my limited EE knowledge, a 55W HID bulb should only take as much, if not less, current as a standard 55W bulb? The BOW harness simply makes up for the differences in the current (ie additional large resistor in parallel) between a 55W HID and the stock halogen so that the CEM thinks the bulb is not faulty. I have not checked the voltage / current that much to know the variations, but a 55W HID on a line rated for 55W at the same voltage, should be able to handle the currents involved.

      Theoretically you're right. A 50 watt HID *should* draw the about the same current in continuous operation as a 55 watt halogen. The difference is not continuous operation, it's the initial startup. When a bulb starts up, it draws very little current at first (~2 amps), then ramps up slowly as the filament warms up (~200 ms for this to happen), and eventually gets to 4.2 amps.

      A 50 watt HID runs steady-state arc at around 700 volts, 3-5ma (milliamps). The problem is to get there, the ballast has to ignite the arc within the HID capsule. This requires ~7,000-15,000 volts depending on the quality of the ballast (higher ignition voltage=better ballast=more reliable starts). The ignition pulse is created using a flyback transformer (like an ignition coil), and if the ballast is poorly designed this will send a transient spike down the power leads. It will also draw 20-30 amps for the first few milliseconds while it strikes the arc.

      After all that madness is over, you are right, the wiring will be fine. It's the initial spike I'm worried about.

      I dislike the idea of the parallel resistor ("BOW harness") since that's essentially running a 110 watt heater in the engine compartment. This would result in a 100% increase in total current consumption, and HID's are suppose to be more efficient, not less.

      Quote, originally posted by fone »

      I'm using a battery harness, aka relay switch.

      Out of curiosity, did you get a bulb-out indicator?

      Quote, originally posted by fone »

      Wiki link says 100 to 120 Hz? Not sure if the PWM requency differs from car to car, could be the reason why some cars are able to fix the HIDs directly, while others needed the DRLs disabled.

      Different PWM frequencies are used for different applications. For example, DC-DC converters work at ~100khz (100,000 cycles/second) and fuel injectors PWM has to be at least 20khz if not higher, to keep up with intake valve operation. Lower frequencies are suitable for incandescent lights, since the human eye can only pick up frequencies lower than ~30hz.

      In any case however, the frequency is fixed by the MCU's clock, which is driven by a crystal oscillator. Unless they change the speed of the CEM processor (not likely during a production run) the PWM frequencies will be the same.

      I doubt the PWM frequency has anything to do with using the stock harness for HIDs vs disabling DRLs. Even with DRLs disabled, the low beam is still PWM modulated (when on). I suspect it has more to do with the HID kit, and said kit's ability to handle transient voltages.

      Quote, originally posted by fone »

      From my limited EE knowledge, a 55W HID bulb should only take as much, if not less, current as a standard 55W bulb? The BOW harness simply makes up for the differences in the current (ie additional large resistor in parallel) between a 55W HID and the stock halogen so that the CEM thinks the bulb is not faulty. I have not checked the voltage / current that much to know the variations, but a 55W HID on a line rated for 55W at the same voltage, should be able to handle the currents involved.

      Theoretically you're right. A 50 watt HID *should* draw the about the same current in continuous operation as a 55 watt halogen. The difference is not continuous operation, it's the initial startup. When a bulb starts up, it draws very little current at first (~2 amps), then ramps up slowly as the filament warms up (~200 ms for this to happen), and eventually gets to 4.2 amps.

      A 50 watt HID runs steady-state arc at around 700 volts, 3-5ma (milliamps). The problem is to get there, the ballast has to ignite the arc within the HID capsule. This requires ~7,000-15,000 volts depending on the quality of the ballast (higher ignition voltage=better ballast=more reliable starts). The ignition pulse is created using a flyback transformer (like an ignition coil), and if the ballast is poorly designed this will send a transient spike down the power leads. It will also draw 20-30 amps for the first few milliseconds while it strikes the arc.

      After all that madness is over, you are right, the wiring will be fine. It's the initial spike I'm worried about.

      I dislike the idea of the parallel resistor ("BOW harness") since that's essentially running a 110 watt heater in the engine compartment. This would result in a 100% increase in total current consumption, and HID's are suppose to be more efficient, not less.

      Quote, originally posted by fone »

      Shouldn't a capacitor do the trick? I'm not too familiar with inductor. ie smooth out the ripple effect of the PWM?

      If you look at the PDF above ( http://theeshadow.com/files/volvo/hidcircuits.pdf ) you'll see all three circuits have capacitors. Inductors are used commonly for filtering (look inside a UPS, or a computer power supply, or a TV, etc...) in the form of an RLC circuit (see wiki is pretty universal and can be tuned to a specific frequency.

      I ordered the caps and diodes for method I. If I can get a decent scope trace after that circuit, I'll try the HIDs.

      Last edited by theshadow27; 10-11-2011 at 12:44 PM. Reason: updated broken links
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      Yes, I have a bulb out indicator, but that would be the least of my concerns as I'm not going to put a resistor there that draws almost 55W by itself, wasting too much energy as another 55W is drawn directly from the battery already.
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    17. #15
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      Re: (fone)

      That would drive me nuts, but I'm about stuff like that (obviously). I ordered 10 of each component (should only need 4) so if it works I'll send you the other set.
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    18. #16
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      I'm actually fine with my current set up. Also, you might want some of the standard HID harness to make the set up plug and play. I might have some spare ones from the damaged ballasts, if you would pay for shipping.
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    19. #17
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      Re: (fone)

      Hmm... I was planning on mounting the electronics inside of the CEM's enclosure, and mounting the HID ballast to the plastic cover plate behind the headlamp. Then it's just two holes in a $5 piece of plastic, and no wire tapping or cutting. I'll let you know if something comes up.

      Until they get here though, I guess there's nothing else to do but wait

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    20. #18
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      Re: (theshadow27)

      I bought both a HID50 "50 watt" H11 kit and the DDM "55 watt" H11 kit out of sheer curiosity for why one could cost $280 shipped and the other $85 shipped... I'll leave the results for another thread, but for the record I installed the DDM kit.

      All factory wiring from the headlight assemblies to the CEM. As I suspected, the PWM modulation from the CEM's voltage regulation prevented the HIDs from working at all. With just the DDM components installed, neither bulb turned on and there was a "low beam failure" message.

      Also, as I suspected, a simple capacitor ripple filter was sufficient to get things cooking again. Here's the circuit I used:

      Each ballast got 5 capacitors and 1 diode. Total cost of parts was $16.30. You can do it for cheaper, but I got all industrial rated components (105c operating temperature). It's possible that 50,000 microfarads is a bit excessive, but it did the trick without breaking a sweat.

      The capacitors being assembled:

      With diode board installed:

      Not the smallest thing in the world, but not that bad either:

      Here's how I tapped into the headlight wires. It's the connector labeled "Front" on the CEM. The wires are green-violet (passenger) and green-white (driver). Be careful - there's two green-white wires. The one next to the green-violet wire is the correct one. Or just flip it over, the pin number are 25 and 37.

      Encapsulated it in silicone, wrapped in electrical tape, tucked it in behind the passenger carpet, and voilà:

      Starts and stops with no issues. Flashes pretty fast too

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    21. #19
      Junior Member ion's Avatar
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      Re: (theshadow27)

      Did you replace this with the Kyle BOW?

      I was considering buying the 55w kit you linked to, but I'm wondering if DDM tuning's "error code eliminator" works. Did you also buy/try their "error code eliminator" or did you just work on making your own from the beginning.

      Also, where'd you get your capacitors from? Digikey is always expensive and I'm hoping you know a better/cheaper site considering you probably buy stuff like this all the time.


    22. #20
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      Re: (ion)

      Id recommend shadows PWM fix rather than the DDM BOW harness if it works with your setup. Its a more proper system than the bow harness which is kinda a band aide.
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    23. #21
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      Re: (ion)

      Quote, originally posted by ion »
      Did you replace this with the Kyle BOW?

      Nope, my ghetto prototype is still working. I was thinking about building another one but (1) I'm too lazy and (2) if it fails (not expected) I'd rather not have to cut through silicone to figure out why.

      Quote, originally posted by ion »

      I was considering buying the 55w kit you linked to, but I'm wondering if DDM tuning's "error code eliminator" works. Did you also buy/try their "error code eliminator" or did you just work on making your own from the beginning.

      Both of the kits I bought didn't work without the caps.

      I didn't buy the error code eliminator as it was $40 at the time and I'd heard all sorts of bad things about them (like most of the DDM failures were the BOWE not the ballast) and I could build it cheaper. Looks like they are $20 now, but mine was $16 or something and Kyles was $14 in parts. Kinda nice to know the quality rather than guessing. If you are ok with 16v caps rather than 25v you can build it for $8.

      But they do work. A hand full of folks are running the DDM BOWE harness without issues, and a few others have had units replaced.

      My biggest problem with the DDM version is that it lives in the engine bay, which is not the best place for electrolytic capacitors. Also not sure if they have a diode, waiting on the one from Kyle to show up so I can rip it up. It should be here later this week, so if you want to wait until then I'll update this thread.

      The other thing DDM is lacking is a proper ground, which effectively introduces more resistance and drops the voltage available to the ballasts. So basically

      Quote, originally posted by ForceFed Motorsports »
      bow harness is a band aide.

      Is correct

      Quote, originally posted by ion »
      Also, where'd you get your capacitors from? Digikey is always expensive and I'm hoping you know a better/cheaper site considering you probably buy stuff like this all the time.

      I used 10k uF (pardon the SI annihilation, nobody measures in mF) caps in the original because I wasn't sure how much capacitance would be required. One worked intermittently so I decided to use all 10 of them... Not very scientific. After mine were installed I ran some SPICE simulations and it looks like 22,000uF is the sweet spot for 55w.

      Mouser is the best bet for high-value caps. The capacitors I used in Kyle's were $5 each (598-80LQ223M025K022) and I bought the last 3 ... After I ordered I was looking over the spec sheet and the 16v are transient rated to 30v so they could be used instead (598-SLPX223M016E3P3) and are only $2.36 each. The diodes were $1.30 from Digikey (497-2738-5-ND) but I've been eying the Mouser equivalent which is $1.20 (511-STPS8L30B-TR).

      The original capacitors I used were $1.65 from Digikey (493-1546-ND), and you'd only need two or three to get up to the required capacitance on each side. It would be about twice as expensive and take up more room.

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    24. #22
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      Re: (theshadow27)

      Quote, originally posted by theshadow27 »

      After mine were installed I ran some SPICE simulations and it looks like 22,000uF is the sweet spot for 55w.

      BTW in case anyone is curious why the DDM's fail, the measurements I got from fone (thanks again m8 ) indicate that it's around 4.7mF. I was able to play with one out of 1SOUL's car in person and his was about the same (3.3mF). Here's what happens 82 times a second using the DDM BOWE:

      You can see the capacitor trying to hold the voltage up (blue), but it's just not enough. It dips below the 9v under-voltage cut off for 2ms each pulse. Also, the ripple current through the capacitor is a constant 6.5 amps! I've never seen a 4700uF cap rated for 6500mA ripple, maybe 2000mA, but that's way out of realistic spec. Add that to a hot engine bay and you can't expect an aluminum cap to last it's designed life.

      When we increase the value of the capacitor:

      the issue goes away. Also, ripple is reduced to 3000mA, the 22mF caps Kyle got are rated to 4300mA. Plus they aren't in the engine bay, so heat is significantly less. In all, they should last much longer...

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    25. #23
      Junior Member ion's Avatar
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      Re: (theshadow27)

      Do you have the parameters for the input signal? Frequency, voltage? I'd like to mess around with some spice simulations of my own. The DDM ballasts just want a steady 13V, right?

    26. #24
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      Re: (ion)

      Quote, originally posted by ion »
      Do you have the parameters for the input signal? Frequency, voltage? I'd like to mess around with some spice simulations of my own.

      Input signal is PWM between 0v and the car voltage - 13.5 nominal

      Frequency I measured at 82hz, square wave

      Duty cycle varies between 70% and 90% depending on input voltage.

      Current for the load is ~4.2 amps, best simulated with a 3 ohm resistor. The real ballast has it's own switching supply which makes it non linear so it's not a perfect replacement.

      According to Volvo the output is suposed to be regulated to 13.0+0.2v. I measure it consistently less than that, around 12.5, but who knows my meter could be off.

      The ballasts will run from 9v to 16v without issues, below and above they have cutouts. That's why dropping below 9v is a bad thing. The goal is minimizing ripple, even if you loose a volt or two it's not a big problem.

      FYI I tried a bunch of configurations: multiple caps, ceramic and electrolytic, pi filter, delta filter, inductors, etc... Nothing worked as well as a single large aluminum electrolytic and a diode.

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    27. #25
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      Re: (theshadow27)

      Okay, got the broken DDM Error Code Eliminator 3 from Kyle today (thanks!):

      Let's go surgical eh?

      I was pretty surprised to find an inductor in there! It's a T-80 iron powder toroid with 22 windings of 16 gauge wire. If it were one wire, according to some extremely rusty math that comes out to about 1uH. However it looked to be split in two windings, and I'm not sure exactly how it was wired.

      The capacitor (which was across the positive and negative, only way to hook it up) was EXACTLY what fone measured, 4700uF. Nice. It's also a decent brand and rated to 105c (another surprise!).

      Couple of hunches on how the circuit is rigged up, my first guess was this:

      but the more I think about the dual winding the less I'm sure about it. No easy way to tell now

      EDIT: Some more looking into the bits that fell off it. Thinking now more along the lines of a inductive t filter:



      Modified by theshadow27 at 7:17 PM 11-11-2009

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    28. #26
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      Re: (theshadow27)

      Interesting, so im assuming the only reason they would actually fail would be due to the heat of the engine bay... being that they actually use decent materials?
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    29. #27
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      Re: (ForceFed Motorsports)

      Quote, originally posted by ForceFed Motorsports »
      Interesting, so im assuming the only reason they would actually fail would be due to the heat of the engine bay... being that they actually use decent materials?

      Oh sorry no - I didn't mean that at all. The circuit is constructed correctly, but is not appropriate for our car.

      With a 4700uF capacitor and a diode there would be 6.5A of AC current ripple running through the cap at all times. If you look at the datasheet the 25v 4700uF cap isn't even ripple current rated! The 80v version is rated to 3A, so the 25v is probably around 2.5a, so when the car is at 13.5v it's getting 250% of it's rated ripple current. Looking at the tan delta coefs it'd be running at close to 150c without the engine bay temps affecting it at all. Being coated in epoxy doesn't help heat get out.

      The 22000uF caps you got are rated to 5.3A ripple continuous. The higher value capacitance reduces ripple so there is only 3A of actual ripple current. It's running at 60% of it's rated value, so heat dissipation is minimal.

      Besides the caps, there's a couple of other problems with their circuit.

      First, it grounds through the headlight wires, which I've measured the resistance of (including connectors) to be around 0.3 ohms. This doesn't sound like much, but it constitutes a 1.2 volt drop at operating currents. Effectively, their cap is working with 11V which makes everything worse (capacitors store charge exponentially), where as ours are working with 13 since the wires to the CEM are huge.

      Second, there's no diode in the DDM box. It's pretty hard to explain why this is necessary, but try to think of a capacitor as a tank of water with a fill and a drain at the bottom. The drain goes to the HID, and the fill goes to the CEM. The CEM feels the need to maintain the level of water in the tank by hooking a garden hose up to the fill. The level goes up, and after a certain point the CEM removes the hose. Well water still goes out the drain, but it also goes out the fill because there's no hose connected. The diode is a one way valve that stops water from back washing out the fill when the CEM disconnects the hose. (jdsr917 - I tried, I really did)

      Third the inductor is a great idea, but is way too small for our PWM frequency of 82hz. As I went over in the original posts, you'd need a huge inductor (several pounds) to dampen such a low frequency significantly. 1uH is nowhere close, it'd take more like 300mH (someone check my math, it's up there though).

      To summarize, if we had 10KHz PWM the DDM box would work perfectly. Even 1KHz it would probably be okay with. But 82Hz? We're lucky it works at all!


      Modified by theshadow27 at 6:42 PM 11-11-2009

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    30. #28
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      Re: (ion)

      Quote, originally posted by ion »
      How do you know it was the error code eliminator that failed? My guess would be that the failures are a result of poor assembly (e.g., bad solder joints).

      Because when one BOWE fails you can move the other to the failed side and it will work. Also, both my car and Kyles now work with my circuit and without the DDM BOWE's, but neither will run without a BOWE.

      The reasons for failure are outlined above, which is I'm guessin why you deleted the post. Sorry buddy I got the email from SS Don't subscribe to many threads, but I was pretty sure nobody would ever reply after the OP so I had to keep an eye on it lol

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    31. #29
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      Re: (theshadow27)

      lol, and here I thought I got away with it.

      Your capacitor current rating explanation makes sense, but I think the circuit might be acceptable if the ballasts have circuitry to handle high frequency PWM input. One possible arrangement of the inductor and capacitor can simply increase the frequency of its pulse input. It'd be interesting to see what exactly the DDM can run off of: maybe by hooking it up to a supply and signal generator.

      Anyways, I ended up buying the DDM eliminators just because I think their solution looks cleaner. If they fail, maybe I'll just get better capacitors for them (if the capacitors are what caused them to fail).


    32. #30
      Member theshadow27's Avatar
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      Re: (ion)

      Quote, originally posted by ion »
      One possible arrangement of the inductor and capacitor can simply increase the frequency of its pulse input.

      Passive components can change amplitude and phase, but they can not change frequency. At the very least it takes a few diodes to double frequency once, and even then it's not rated for anything more than a few mA. The headlights run at 4.23 amps each.

      Not sure where you're going with that, but by the time you build a circuit to increase the frequency of the PWM to what the internal filter capacitors (arranged like mine, just smaller) in the ballast can handle you've far exceeded the cost of my circuit and the DDM...

      Quote, originally posted by ion »

      Anyways, I ended up buying the DDM eliminators just because I think their solution looks cleaner. If they fail, maybe I'll just get better capacitors for them (if the capacitors are what caused them to fail).

      A lot of people are running the DDMs without issue, but there's also a good number that fail. I agree that it is a "cleaner looking" solution.

      I wish there was a way to correctly do it the way DDM did with an in-line box, but there's not. I'm working with a company called Retro Solutions to come up with a commercial variant that looks less DIY, but it will at the very least require a real ground tap.

      Not sure how you would replace the capacitors in the DDM units, the whole thing is potted in epoxy. If it came apart easily I wouldn't have attacked it with a saw to take pictures. If you somehow manage to get it apart, you might as well start from the beginning and do it correctly with bigger caps and a diode...

      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    33. #31
      Junior Member ion's Avatar
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      Re: (theshadow27)

      LC circuits are commonly used as oscillators. I mean yeah... the output is no longer a square wave (an oscillation at each edge that lasts the duration of the pulse), but that doesn't really matter, it's a higher frequency signal that the ballast might (apparently can) process.

      As for replacing the capacitors, you said "semi-rigid". Is it kinda rubbery or completely solid? I was thinking maybe it could be heated up and scooped out or something. Might not be pretty, or worth it, I didn't really think it through.


    34. #32
      Member theshadow27's Avatar
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      Re: (ion)

      Quote, originally posted by ion »
      LC circuits are commonly used as oscillators. I mean yeah... the output is no longer a square wave (an oscillation at each edge that lasts the duration of the pulse), but that doesn't really matter, it's a higher frequency signal that the ballast might (apparently can) process.

      I see where you're going, but a filter and an oscillator are two entirely different ball games. A pulse can induce an LC circuit into oscillation, but it's at very small voltages and currents. To get a decent 4ms long ring-down that could supply 4.23A would take a... I'm not even going to try to do the math... Godzilla capacitor and a Stay Puft Marshmallow man inductor. Plus it'd have to take voltage up to 24 volts (since it's a DC biased AC signal).

      The only practical way to use oscillation to increase the frequency between modulations would be to use a LC behind a MOSFET. If you're going that far, you might as well use an RC behind the MOSFET so that it gave a solid current rather than a rapidity pulsating one. At that point you have transistors and resistors and capacitors and circuit boards and a +12v source and it's just all not worth it.

      Quote, originally posted by ion »

      As for replacing the capacitors, you said "semi-rigid". Is it kinda rubbery or completely solid? I was thinking maybe it could be heated up and scooped out or something. Might not be pretty, or worth it, I didn't really think it through.

      Yeah semi rigid epoxy. That's the stuff that if you put in a vice and squeeze it won't crack (tried that) but it's completely solid. There's no good way to remove it - epoxy is a polymer reaction so heat won't matter, and it's probably impervious to most solvents other than 40% HCL which would destroy everything inside anyhow.
      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    35. #33
      Member -ForceFed-'s Avatar
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      Re: (theshadow27)

      Being that my BOWE harness is sitting above the CEM id say thats pretty clean
      Current: 11 ISF | P2 V70R
      Past: 14 C300 AMG Sport+ | E46M | S40 T5 | NA1 NSX | Acura TL | LS-T DC4

    36. #34
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      Re: (ForceFed Motorsports)

      I think the DDMs are "cleaner looking" outside the car since they have non-destructive connectors. Installed, the DDMs have an unappealing aftermarket look to them, where as mine if done correctly look to be part of the stock harness until you remove the connector. No boxes dangling in the engine bay. I'll try to get a pic of where I mounted my ballasts, it's ridiculous.
      '05 S40 T5 AWD M66 sport/winter/ew. Michelin PS A/S+. 6000k 50w HID low/HIR1 high/full LED conversions. RiCA SW. Evoelate intake. IPD rear sway, skidplate, TCV.
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    37. #35
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      Re: (theshadow27)

      How our fenders roll inward water just gets dumped on the top of our head lights, so I cant mount my ballasts like factory on the back of the head lights I dont think. Probably make an extension harness and mount them behind the bumper or further down into the fenders.
      Current: 11 ISF | P2 V70R
      Past: 14 C300 AMG Sport+ | E46M | S40 T5 | NA1 NSX | Acura TL | LS-T DC4

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