jeepnutt

Tried looking it up with no results. As some of you might know the TIPM sends out a pulsed signal (on-off-on-off-ie..)to the head lights ,so the bulbs can last longer and use a smaller gauge wire to them. The reason for all this is, im going to upgrade the bulbs to a much higher wattage, i already have the IPF lens on the JK now. I made a relay harness,hooked it up and sure enought it was buzzing (turn on-off-on) like crazy (It was a little weird hear the relays buzz and looking at the headlight on and not seeing the flash>). I knew this could be a problem when i made them up but thought the relays i got wouldnt be effected by the pulse. I'm going to install a couple of capacitors into the harness to the relays to help smooth out the headligth signal. SO knowing the flash rate would help with getting the right capacitor. When im done with this project i'll post it so you all can see.

ronjenx

Measured with two different instruments....

Headlights on with engine running:
78% duty cycle; 90Hz

Headlights on with engine off:
0% duty cycle; 0Hz
(I would have thought always on would be 100% duty cycle. But, I guess it means there is no cycle to measure.)

thechad07

I don't know the flash rate, but... After a lot of forum reading, I found someone that used 470uf capacitors across the coils of the relays. Supposedly they worked great. I have a pile of the caps but have not tried them yet (they are pretty cheap on eBay.) I hope this helps.

~Chad

demp

I've been meaning to test this but never could find time. Thank you for measuring that.

Depending on the relay's cutoff voltage you may have a very tiny gap with a 470uF, the relay may not even respond fast enough to it.

If the frequency is correct you have 1s/90 = 11ms for each pulse on and off.
With a 20% off time you have a window of about 2.22ms.
Using the current draw of your relay and assuming 12V, you can divide the voltage by current to get resistance.
The simplified Discharge formula for a capacitor is Resistance * Capacitance. 470uF is 0.000470. The time will be the result in seconds to discharge to 37% of the original voltage.

The same information could be used for those wanting to use LED lights direct from the factory harness, just consider a bit more current draw from the light when getting parts.

My math may be off, it IS monday morning :p

GJeep

Indeed. For 0Hz, the cycle is infinitely long. Therefore, there's not even one complete cycle, so the reading of duty cycle is zero.

Rednroll

Usually the Percentage number of the duty cycle is % ON, followed by the % OFF of one pulse cycle, where the % OFF number is usually not given when talking about "duty cycle". So when you say 0% duty cycle with the headlights on, and engine off is 0%, I'm a little confused. Do you mean 100% duty cycle? Then further when you mentioned 78% duty cycle, is that 78% ON and 22% off?

ronjenx

78% duty cycle means power id on 78% of the time, and off 22% of the time. It does this 90 times per second.

The highr the duty cycle %, the longer the power is on. That's why I feel 100% should represent on all the time.
I think when the meters I used see no cycling, so it reads 0% duty cycle.
So...
With the engine on, the headlights get pwm voltage.
With the engine off, the headlights get pure 12 volts.

Rednroll

Instead of using a capacitor, where you would actually need a pretty large one to work with a 90Hz square wave, you might want to consider using a solid state relay instead. Using a capacitor could actually damage the light circuitry due to the in rush current of charging the capacitor. Where if you used a solid state relay, it would serve the same purpose as your relay and not make any clicking sound.

Rednroll

Ahhhh....yes!!! Now, I understand. You used a digital meter to get the duty cycle, which would read 0% if it was on 100% of the time. I'm used to measuring these things with an O'Scope.

jeepnutt

Thanks rednroll, ronjenx and thechad07 for the info. it helped. So gen 1 was 2 20 amp relays, 2 bus bars and 2 15 amp fuses. It worked but buzed like crazy. So gen 2 i added 2 1000uf / 35 volt capacitors in a extra box. see pic
[IMG][/IMG]
black relay housing, clean top one the cap housing. Hook it up and it worked. No buzzing at all. But i did dropped the lens and blew out the low beam on the bulb. But i did check hi beam and it worked fine.
I started to work on gen 3 which will have 2 35 amp relays,2 20 amp fuses, 2 1000uf /35volt caps, 3 6amp diodes, 5 bus bars, and a sh!t load of wires, terminals and more wires and terminals. see pic for diagram
[IMG][/IMG]
I change the caps to the barrell kind with both leads coming out the same side.
I should be done with gen 3 tommorrow. i'll post some pics too.
Now i know there be alot of talk on the subject and i read some heated debates on it. Im no guru with eletronics, the 12 volt system maybe?? To Rednroll id tried to fine the solid state relay you mention and i did fine one, but its was $60 and huge as hell. I think this set up should work and not cause any back feed problem to the JK and the tipm. Oh by the way all those circle in the diagram are the term holes the the housing im using and the views a from the back of all those housings.