I remember a '91 Sunbird I had with Daytime Running Lights, and one of the things I will never forget about it was the soft start which turned the high beams on niiiice and slow when the car started. It looked great and I wish I knew how it worked.

Which leads me to my question, why was the DRL module configured this way and could I ever wire my Dart's headlights to come on this way when I pulled out the headlight knob? Well with a few differences; firstly only when I turn on the headlamps, and with full illumination, not half, and on whichever beam Ive selected. I think this coupled with those yellow Cibies would really hook the eyes.

I'm guessing capacitors and diodes factor in here somewhere, am I right?

I bought a kit from Wal-mart, made by Rallye, for daytime running lights for anything. (Except lawn tractors, I think) If the weather co-operates tommorrow, I'll hook it up and let you know if that works.

The capacitor/diode approach is correct. Failing anything else, pull the module out of a donor Sunbird and wire it in. Just make sure you know how to wire it proper.

I'd be more than happy to mail you a xerox of the instructions for this kit, as I'm sure it would work with that module. It does sound . PM me an address.

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IS 40:31 gets me through lifes challenges.

I already thought of that, but the DRL module is designed to be wired in to the high beams, and they only illuminate them about 50%, probably due to an internal resistor. It's tough to think your way through a solid block of epoxy I think the only way I can wire a soft start on my headlamps is with individual components, but Ill be damned if I know which ones or how.

As far as I remember, the DRL module is wired to the coil to turn the high beams on at 50%, and is wired to the headlamp switch to cut out so the headlamps can resume operation, through an external relay I believe. I just don't know what's inside that module so I can build one for my own purposes. I'm sure I could just wire a large capacitor in parallel with my positive wire coming off the headlamp relay so the voltage will slowly increase as the capacitor charges, but how can I abruptly cut power to the headlamps when I turn the switch off, and still have the capacitor discharge so it will slowly turn the headlamps on again the next time? And how do I size this capacitor to give the turn on rate I want?

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

If you rig the switch so that in the off state it grounds the + of the capacitor (effectively shorts the capacitor terminals) that will discharge it quickly, but could be disasterous to the cap if you keep doing that over and over.

Hm I could dig up the formulas if I looked through my college engineering textbooks, but I believe you would need to know the total current drawn by the load or else your calculations would be thrown off. Try searching google for "capacitor charging formula" or something similar, and I'm sure you'll get somewhere if you keep trying. As well, remember capacitor rating tolerances can very quite a bit, I've seem some tolerances up to +100%. I would predict you would need quite a bit of capacitance, nothing you can buy at radioshack.

Hm, I could make a similar module like that quite easily with a microcontroller and some mosfets.

Oh, I know,,, I could go real crazy with a PWM power supply, this idea is just spinning out of control lol. It seemed like such a simple thing on the Sunbird and looked so good. Those car stereo shops sell 1 farad "stiffening caps" for ridiculous prices, in fact I still have a 1/2 farad Harrison capacitor that might do the trick, if it isnt too badly sulfated from years of storage. Maybe ground it through a ballast resistor? I really have to do some math, Ive been putting it off.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Y'all are *seriously* overthinking this.

There is no soft-start circuitry in any DRL module. The reason the high-beam DRLs come up slowly is because -- depending on the model of vehicle:

1) The left and right high beam filaments are in series with each other, or

2) The left high and low beam filament and the right high and low beam filament are in series with each other respectively on each side of the car, or

3) The module uses PWM.

I'm not too sure why you want to soft-start your regular headlamps. Seems to me there's way better stuff to spend money, time and effort on.

As far as Daylight Running Lights, see my previous post in the other lighting thread.

Theres nothing real crazy or serious about it... one mosfet, one 8 pin uc, and a 5v regulator is all thats needed. Hm, and maybe a small power transistor depending on the mosfet you use.

I can see it taking no more then 10 lines of code... start the pwm, increase duty cycle x% every y ms, once you approach 100% you turn off pwm and turn on the mosfet continiously. Voila

Large caps could do the job but the delay will not be terribly consistent amongst change in ambient temp (maybe +/- 1s at extreme temperature swings, whereas a uc would be like, +/- 1ms?) . Stereo stiffening caps would probably be a good choice but take up room, especially if you want to tuck it all under the dash. Check partsexpress.com for cheaper generic car audio caps, and also apexjr.com I got some 1/4F caps from apexjr for $3 each a few years back.

...

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.