Procal DRL question

[chasinternet]

I used the Procal to program the Daytime Running Lights on my 2008 (bought 11/2007) JK Unlimited Rubicon.

Has anyone heard of the instruction being reversed where the high beam setting actually gives you low beam DRL and visa - versa?

No biggie - just a sanity check.

It may be my JK is more special than I think :D or because no one would notice the difference and I'm just the first one to have tapped the headlight connector for test equipment. Both low and high beam DRL runs on ~18.5% duty cycle which isn't very bright so doubt it would be noticed. (See oscilloscope output at http://www.jkowners.com/forum/showthread.php?t=22065)

I checked and rechecked because I could not believe mine does that since I have not found any posts talking about this.

I have used a variety of functions on the Procal and all those work the same as in the instructions.

[AEV Jordan]

chasinternet,

I just got done reading the thread over there. The guy named Rednroll seems to have a decent grasp as to how the systems works. But no one in that thread is exactly spot on. Let me explain a couple things.

The TIPM does in fact do most of the vehicle high voltage driving. The light in the JK and the fans in some other vehicles are PWM to save on weight, cost, size of wire, and to use less current (keeps the alternator off). PWM is a great way to get 95% of the light from the headlights while using 85% of the power. This seems to be understood.

You make the mistake of looking at the PWM cycles as constants. They are not. The TIPM will monitor current battery voltage and alternator output, to factor the duty cycle (on/off times) of the lights. They do this with a known bulb coefficient. The other thing to note is that RMS of the wave is not exactly the absolute voltage the bulb is seeing. When the bulb is unpowered it will glow for a little while. So, by using an appropriate cycle they can cut the power without cutting visible light. For instance, it may only take 17% ON time to get a nominal or equivalent voltage of 6V for the DRLs at idle. It may take 25% on the highway or 12% when coasting. So don't get too caught up in the duty cycle. To see 78% and say that's why the lights suck is definitely not correct. They're at ~85+/- when driving. I've found that reflector style/shape/cutouff to be just as important as bulbs. The system monitors to average RMS output to be something like 13.2V of equivalent voltage, since the bulbs are optimized at 12-13V this is where they should be. Less heat, longer life, less power, just as much light.

Another thing is, that while backfeeding pulses like those from unpowered relays do infact destroy FETS/Transistor gates, the TIPM has diode protection already in place for this. It bugs the hell out of me when I see people add diodes on DC PWM lines :) They are needed for AC lines, see examples of how bridge rectifiers work. On the DC headlight lines however, all adding a diode in series will do is cause 1-1.7V to never get to the lights. See the forward drop of the diode to be used. This should be avoided whenever possible. The lamp won't care if there is a little backfeed spike, and the TIPM doesn't care because the engineers in charge have already put the protection in place. The light circuit was designed that it could be shorted to ground or battery at any time.

There is an issue with tapping the highbeams for driving lights or low beams for fog in cars that use PWM for DRLs. We are working on a fix for this on an upcoming project. In the mean time, capacitors work fine to buffer the line to drive a relay from, I wrote a lot on this subject in another thread here. The best hardware solution would a low pass filter to the relay (exactly what the capacitor is doing) or a buffer (Opamp in voltage follower mode with a filter, same as the cap but on a separated line), or latching relay. Of all of those I would probably try the capacitor, just know they do not last forever and when it dies it can short (meaning no lights when you least expect it).

You're on a pretty good start. Find something that will work and try it out. I wouldn't try an reinvent the wheel just yet. :)

[JeepinJon]

To see 78% and say that's why the lights suck is definitely not correct. They're at ~85+/- when driving. I've found that reflector style/shape/cutouff to be just as important as bulbs.

Does AEV have a fix for this issue that they reccomend? The new IPF lights, or is there something else out there worth waiting for?

[AEV Jordan]

Can't get into it. You know that :)

[JeepinJon]

I heard about a year ago something is in the works. I will put in my IPF replacements that should be here tomorrow until I see some on your site. ;)

[chasinternet]

AEV Jordan,

Sorry, I just read this.

I understand what you are saying about the duty cycle - thanks. The 78% why lights suck with the crying emoticon was my bad sense of humor. I did increase the throttle and to my surprise nothing happened but I must not of done it long enough.

Re: the diode in series. I don't get that one either and now that you explained I get it even less - I'll avoid it. The diode in parallel across the relay coil is often done - although that gives other problems.

Re: TIPM protection - probably the automotive Transient Voltage Suppression diodes I later mention but the theory is putting spikes on the line is bad practice and from what I read - those protection diodes do eventually fail if they are subjected to constant spiking. I don't know what in a semiconductor device fatigues but I read it in several places without explanation or failure rate.

I'll look for your other thread (EDIT: I found it http://forum.aev-conversions.com/showthread.php?t=1437)

As I mentioned over there since I use to do sales for capacitor manufacturers - I've seen the carnage from capacitors failing shorted and I was trying to avoid them. Perhaps a matter of familiarity breeds contempt - LOL.

BTW - you didn't say anything about my AEV instructions being reversed or is it my Jeep is special?