My cool driving light setup

[prginocx]

I wanted two things in my driving light project. Good bright halogen lights ( 60+ watts ), and protection against leaving them on by mistake. I came up with the circuit below. The chip turns on the relay ONLY if the driving light switch is ON AND the headlights are ON. My truck has a buzzer that warns you against leaving the headlights on...So I can only use these lights when the headlights are ON.
The NUD3160 chip has extremely low gate current (< 0.5mA ) so most any circuit you tie it into won't be affected. All I did was pull out the headlight switch, and find a wire (Brown) that gets energized when you turn on the headlights. You can imagine lots more uses for this cool chip, since it can turn on a relay, but it doesn't affect the circuit you connect to....

Manufacturer PN NUD3160LT1GOSCT-ND Digikey carries several types. Unfortunately it is surface mount. I believe it maxes out at 200mA load, so it will drive most relays. It is intended for automotive applications.

Arrrrgh...Evidently my schematic is too big to load, email me if you want [email protected] ( changed to Jpeg, hope this works )

You must be registered for see images attach

 

[thered95]

why? you dont need that chip, the amount of draw on the switch is nothing. i would be more worried about the headlights burning out the switch not the relay.

 

[prginocx]

why? you dont need that chip, the amount of draw on the switch is nothing. i would be more worried about the headlights burning out the switch not the relay.

Well, whenever I connect to some other GM circuit already part of the wiring harness, I want to affect that circuit as little as possible. Sometimes in the past, I've used some signal from some circuit, and everything seems fine, but two weeks later, 850 miles from home, you find out the little bit of current you drained out of the existing circuit WOULD cause a problem, but only after dark, with the camper loaded, and towing the boat. So I was trying to find a way to use voltage from the headlight circuit, and turn on the foglight relay, but not really use any current from that existing headlight circuit. I have the stock type headlights where only one light is on for high beam, and the other light is on for low beam.

However, I needed that signal from the headlight circuit, because I ONLY want the fog lights to be able to turn on when the headlights are on....That way I can never leave them on by mistake and drain the battery. I believe this chip might have other applications too, you could probably tap into almost any existing signal without affecting the ECM.

Only a tiny amount of current goes through the foglight switch, which gives you a HUGE selection of switches you can use...

 

[thered95]

if you are worried about something burning out i would install a relay harness on the headlights. this will take all the lode off the switch. you could even go as far as to do the same for the parking lights. the issue with these trucks is that nothing has a relay. so all the current goes trough the switches. so when you turn on your highs all the power is running trough the failure prone multifunction switch. adding a relay harness eliminates this issue by making the switch only have to switch a relay. when you do a harness you can add the high-4 by just adding a diode between the trigger leads.you can also have the same switch trigger something else like fogs with just a diode

 

[prginocx]

if you are worried about something burning out i would install a relay harness on the headlights. this will take all the lode off the switch. you could even go as far as to do the same for the parking lights. the issue with these trucks is that nothing has a relay. so all the current goes trough the switches. so when you turn on your highs all the power is running trough the failure prone multifunction switch. adding a relay harness eliminates this issue by making the switch only have to switch a relay. when you do a harness you can add the high-4 by just adding a diode between the trigger leads.you can also have the same switch trigger something else like fogs with just a diode

I have heard about the problems with the headlight switch, that is why my fog light setup uses a relay and only draws its power from the firewall terminal block. So far my headlight switch is working fine knock on wood.

If I was to go the 4 light ON setup, I'd definitely use a couple relays, the wires on that headlight switch don't seem very beefy to me...

 

[great white]

Credit given for the design, but it would have been just as easy and simpler to tap the headlight wire (behind switch) to the fog light switch then out to the relay. Then power the lights from the relay as per normal.

The fogs go on and off with the headlight switch regardless of the fog light switch. The fog light switch just makes them selectable.

Cool little circuit though. If it meets your needs then rock on....

I'm a little bit more "relayed up" than that for many things:

You must be registered for see images attach

 

[prginocx]

Credit given for the design, but it would have been just as easy and simpler to tap the headlight wire (behind switch) to the fog light switch then out to the relay. Then power the lights from the relay as per normal.

The fogs go on and off with the headlight switch regardless of the fog light switch. The fog light switch just makes them selectable.

Cool little circuit though. If it meets your needs then rock on....

I'm a little bit more "relayed up" than that for many things:

You must be registered for see images attach

Ah, but you see, if you tap the headlight wire, you are drawing that power to drive the relay coil. That is what I'm trying to avoid, in some cases, you can't draw power from a circuit without causing problems later on....Difficult to anticipate what problems might happen, especially with ECMs on newer engines and such....I remember how I tapped into an instrument light circuit on a '96 Olds, and everything seemed normal, but later on I found out it was causing a false reading from the O2 sensor, which was causing all sorts of other problems. That was my first really bad experience with the consequences of drawing power out of a circuit, even though most relay coils don't draw that much current.

HA, I spent 3 months screwing around with that Olds 02 sensor issue, it was always giving error codes on the ECM and such...And wouldn't idle worth a damn. I learned a hard lesson about tapping into certain circuits depending upon how much current you steal away...That is why I invented this circuit, it draws a TINY amount of current, but you still get your signal to activate a relay.

 

[great white]

Your concerns are noted. However, tapping the headlight switch wire in the way i have done it draws less power than the oem setup...I power the headlights through a relay and the switch is only a trigger in the circuit.

Even so, in these trucks you can "steal" the minimal amperage to drive a relay off the headlight circuit and it will have no ill effects on the rest of the electronics.

But like i said before, cool little circuit you have and if it does what you want then rock on.....