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Discussion Starter · #1 ·
::)

Not anymore. The easy solution is to just turn them off. That won't work though.

So I was pondering, "how can I automatically turn my lights off"?

If I go through the ignition switch, anytime I need light but key off, it won't work.
If I use a oil psi switch I can once again only have headlights with engine running.

So I want headlights that turn off below a certain voltage, thus leaving me enough to crank the engine, but otherwise operate normally.

They sell a device that cuts off everything once voltage drops below 11.xx volts, and will then only let you crank engine while holding brake pedal down. Sounds too complicated, and by time 11.xx volts is reached, you are almost stone dead.

They always told us 12.45ish is about 25% discharged, or 75% left. Seems like a suitable place to have headlights shut off.

Couldn't figure out exactly how to trigger this sequence automatically. Not so electronically inclined. Go figure.

What I am thinking is, maybe I can use zener diodes? Electronic version of pressure "pop offs" only allowing voltage to pass through when it is above a certain threshold. I am wondering if I can take (2) 6.2V zeners in series, so voltage only passes through above 12.4v? Can I then attach that output to a NPN transistor to switch the ground side of a normal relay?

It seems like anytime voltage was higher than 12.4, there would be some current flow through the diodes, which would trigger the transistor to apply ground to the relay, and turn headlights on. When voltage fell below, the relay would shut off. Is this correct? If so, I think I could do this for under $10, and at the same time upgrade to relay controls for headlights instead of running all the current through the switch. Double whammy?

I don't imagine I will find a lot of electronically savvy individuals here, but I would rather chance that, as opposed to get in over my head on some electronic forum and have to try to fight off nerdy overkill circuit designs.
 

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s ǝoɾ said:
::)

If I go through the ignition switch, anytime I need light but key off, it won't work.
Why can't you keep the switch, bypassing the ignition? Then it'll work with the ignition on, but you can manually override it if you should need headlights on with the engine off?
 

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Discussion Starter · #3 ·
ToxicDoc said:
Why can't you keep the switch, bypassing the ignition? Then it'll work with the ignition on, but you can manually override it if you should need headlights on with the engine off?
Are you talking about auto-on DRL? The kind that come on when ever the ignition switch is on?

If so, that could potentially work, by reducing the amount of times I actually use the HL switch, but the first time I did use it, I still could be left back at square 1.

Now for some back ground. I haven't done this (leave them on) in 6 months. For a while, a lot of my driving was at that breaking point of dawn. So I traveled with my headlights on just as a safety feature for others. By time I would get to my destination, it would be light enough out that I could not see they were still on. 8-10 hours later I would come out and recognize the low orange glow of the head lights as I am walking to my truck. It would grunt, voltage dropping down into the single digits, and luckily fire, but still a close call.
 
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I think what doc meant was, run your HL switch to the ignition so if your toggle switch is off, the HLs only work with the ignition on. But if you want to use your lights with the ignition off, you'd have to flip both the toggle and HL switch.
Bacically, toggle off= lights only work with ignition on. Toggle on= headlights work as they normally do from the factory.
 

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Discussion Starter · #5 ·
I'm trying to visualize that schematic in my head.

So the center pole goes to the head light switch, with the original HL feed wire removed.
One outer pole is connected to ign switch
The other outer pole is connected to some batt feed source such as the original wire removed from HL switch?

Is that sound right?

Memorizing not to play with that or leave it in the wrong position may prove difficult, although the amount of times using the other switch position would be very limited. Don't ask why exactly I need lights on and ign switch off, I don't have a good reason at this exact moment, although I know I will find one the moment I devised a circuit that eliminated that function. There must be a reason the oems all design headlights to come on even w/o key on.  {think}
 
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Maybe something like this?(excuse the caveman drawing)



Sorry I'm not the best when it comes to these things, also I'm not sure if you can wire a ign. switch to ground. But it could be reversed.
 

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I'm thinking about a timer.  No matter what, you don't want the headlamps to stay on very long without the engine running anyway so just wire in a constant duty relay in the headlamp circuit that is on when the ignition is on.  When the ignition goes off, the timer keep the circuit closed and the headlamps on for a set amount of time.  You could override it with either a toggle or by leaving the ignition on.  The amount of times that you may want the headlamps on without the engine running are going to be few and even then you want to cut them short to preserve the battery.  During those few emergencies you could keep the headlights active with the toggle switch and either keep in mind what you are doing or go redundant and use one of the Battery Buddy deals you mentioned before that trip off when the battery gets low.

Or add a second battery for things like lights and so on and keep the other for engine starting only and not worry about it as much, lol.  Just my .02
 

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Discussion Starter · #8 ·
See, the timer is not a bad circuit either, as this allows that high tech cool "lights shut off 90 seconds later" thing you see on new cars.

I have a second battery, I just have not took the time to isolate them, and separate various circuits. I WILL do that, although I still want something to shut my lights off if I don't do it myself.

The circuit I was talking about is basically a battery buddy (battery brain), but with a higher cut off limit and instead of costing $70-$110, would cost $5+relay (which I will be adding anyways)

May have to combine multiple ideas as they come along.
 

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Sounds like a plan.  I like simple, as in I can repair it on the trail in the middle of a rainy night with a roll of electrical tape and a pocket knife simple.  While building something like a voltage sensing trigger is not over my head, knowing how it all works well enough to make it work when it breaks in the middle of nowhere is over my head.  If I went that route, it would have to have a nice simple way to bypass it like unplugging it from the harness and plugging the harness together in place of it or some sort of jumper harness for emergencies.
 

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Discussion Starter · #10 ·
With the original proposed voltage trigger only acting as a ground for a relay, it would be easy to bypass. If it goes stupid, zeners tend to fail in the closed position, meaning the headlights won't turn off automatically, they will require manual turning off from normal dash switch.

If transistor fails, it may fail in the open or closed position. If it fails open, you unplug 1 wire from pin #85 and provide it a jumpered ground capable of carrying .1 amp.

All of the added few components are only responsible for about .1amp current flow, and are not involved in the direct path of the lights.

If the relay itself fails, a heavy duty jumper is required between #30 and 87 of a standard relay, or you just install your spare one.

Now, I'm just not sure the proposed circuit will actually work to trigger a relay. I did not compensate for drop across the diodes, nor did I calculate how much will pass through and if that is enough to trigger a transistor/solid state relay to trigger the normal mechanical relay.
 

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You could wire your horn relay to blow the horn if you leave your lights on with the ignition off.....

Or, put a stinking little buzzer under the dash.
 

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workgoats said:
Or, put a stinking little buzzer under the dash.
That thing never worked in my truck (factory "your lights are on" or "you forgot your keys" buzzer), unless there was a Blown Bulb, Short in the Wiring, ect.. The Buzzer and my 4WD Light (which never worked either) would kick on any time something electrical would fail or short :eek:

I'll post up a Wiring Diagram that may of be of use to Joe during my lunch break ;)
 

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workgoats said:
Or, put a stinking little buzzer under the dash.
;D X2!

I was going to say.....Sounds too complicated, just listen to the damn buzzer when it goes off. Works for me.

You need kids Joe, that way you can budget your limited time to projects that are actually useful! ;D
 

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My 2000 Jeep Cherokee has a timer that turns the lights off should you leave them off after the key is removed from the ignition.
Maybe you could grab the relays and wiring out of that and graft it in your truck?
 

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What about wiring it up so you can keep the lights on with the vehicle not running but the key in the acc or run position? I assume you shut it completely down and take the keys with when you head into work.

Only problem with this setup would be that you wouldn't be able to turn the lights on without the keys in the ignition and it turned to the acc/run position. You could take care of that by having an override switch to allow it to happen. Maybe a two position that switches the voltage input from a constant on to a acc/run and sends it to the oem switch or wherever you're sending the voltage. If you're worried about leaving this switch on, wire in an annoying buzzer or light to it so you're reminded that the switch is in that position.
 

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My suggestion was to relay in an ignition-activated headlight.  Mind you it isn't as sophisticated a circuit as what you're looking for, but it will work easily.  You'll have headlights on at all times while the key is on (you could wire is a de-activate switch to turn it off when you don't want or for extra current during starting) but it will turn off when you turn the key off.  it's a simple idea that should work.
 

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Discussion Starter · #17 ·
KThaxton said:
I was going to say.....Sounds too complicated, just listen to the damn buzzer when it goes off. Works for me.

You need kids Joe, that way you can budget your limited time to projects that are actually useful! ;D
1st off, I don't have any buzzers. 2nd off, I wanted to learn more about electronics regardless. Unfortunately the nearby college kept trying to enroll me in a $80,000 course that I don't have interest in. 3rd, it doesn't appear complex with 3 components fitting on a postage stamp.

We are talking about 3 components, 2 wires a (+) sensing wire and a ground wire. Prices of about $1/pc for components. Now I just want to find out if theoretical circuit would even work. Pat is probably the person to ask, since I know he mentioned building a microprocessor controlled unit to turn on/off a fan.
 

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Discussion Starter · #19 ·
440 4spd Power Ram said:
Take a look at RC Li-po voltage cutoffs, one for a four cell Li-po shuts off at 12.5 volts..
Not gonna lie and claim I even know what or where that is. ;D Heading to google right now.
 

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s ǝoɾ said:
Not gonna lie and claim I even know what or where that is. ;D Heading to google right now.
It's what keeps Li-po batteries from being over discharged, a small one for a R/C plane is good for around 10 amps constant draw.
 
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