Wiring question

thanks for the help, MM. But if you had read the post, you would know that the whole goal here is to have the headlight come on WITHOUT a switch and AFTER the engine is running. You are correct that it would be much simpler to just use keyed power, but that is not what I want. One reason being that with these high comp pistons, turning over the motor really sucks juice out of the battery. And since I removed the kick started, this is a much bigger deal.

kzmason wrote:

Loud, I built it and have yet to try it out. I have a question though. Will it still trigger i standard bulb is replaced with an LED bulb?

LED for the neutral light? Yes. R1 is there so you don't even need a neutral light for the circuit to work. The circuit is made to work regardless of what is used as a neutral light. I did that in case the neutral bulb burns out.

The Milkman wrote:

Why not just wire a double pole relay into the starter circuit (the bosch type that have 5 contacts instead of 4). Feed constant ground to one of the relay trip contacts. Feed starter power to the other relay trip contact. Feed keyed ignition power into the closed center pole so whenever the key is on the light is on (the normal outer contact for that pole goes to the headlight. When you hit the starter button and the relay closes the other pole contact (that isn't connected to anything), the headlight will be switched off. Then when the bike starts and you release the starter button the relay is turned off and switces back to feed the original pole and turns the headlight back on.
The relay will use much less power than having the headlight on while cranking will. It's late, I hope you understand this.

I understand what you are saying, and that is how it would be done if all you wanted was to give that battery a little extra power for starting. However, there are situations when you don't want the headlight on at all until you are ready to drive off. I notice it most outside of a bar when someone gets ready to leave and they light up the crowd with the headlight then sit there idling while chatting. It makes everybody squint. I guess we could call this circuit the "late-night headlight-etiquette-circuit". :laugh:

PLUMMEN wrote:

id just come off acc side of ignition switch so it comes on when key is on;)

That will eat batteries. My KZ750 B4 has the ehadlight "always on with ignition" and it is really hard on the battery to have to crank the starter with the headlight on. My batteries lasted an average of 18 months that way.

I rewired my bike with a normally closed relay that opens when the starter is energized that takes all of the lights off during starting. My batteries last about 5+ years now.

loudhvx wrote:

I think I also once designed a headlight circuit for when the battery voltage goes above 13.5v or so.

Good idea, except the light might go out at night when sitting at idle.

bountyhunter wrote:

loudhvx wrote:

I think I also once designed a headlight circuit for when the battery voltage goes above 13.5v or so.

Good idea, except the light might go out at night when sitting at idle.

No no. I had it with a latch. Once it's on, it would stay on regardless of voltage. But that circuit took more parts than the neutral switch, and took the control away from the operator. Also, there was no way to override it if you want headlight without the engine running. The neutral switch gives much better control options.

I can't believe I pulled it off. It was definitely and ugly job. I couldn't believe it actually worked that first test. It has been working great since. I still haven't figured out what to do about a housing unit to protect it from the elements.

My question however is for loud. Does it need a certian voltage level to operate? A couple of times, after I think I had drained the battery a bit doing testing, I would turn the key on and after a second or two, the HL would come one without the gear change. Did I do something wrong? Or, is this what happens if the voltage gets low at the battery?

That really shouldn't happen. If the neutral switch is making a good connection to ground, the light should stay off. However, if the neutral switch is not grounded well to the battery, there is a chance the light will come on. If you were using the starter a lot, it's possible the ground wire from the motor/engine case to the battery had a bad connection due to dirt, and using the starter could heat it up further increasing the resistance. That could cause the light to trip on. When that happens, measure the voltage from the engine case to the battery negative post. If it's more than several volts, that would explain it. By the same token, when it's in neutral, measure the voltage on the neutral wire. It should be zero volts, but if it's several volts, it's getting close to trip the circuit. Of course, if the neutral wire is flakey, that would cause it to. The most common place for the weak spot would be where the harness goes from frame to steering area. Try turning the key on and turning the steering to see if that triggers it. Then it's a bad neutral wire.

Post edited by: loudhvx, at: 2008/03/07 16:08

If that's not the problem, there is a slight chance the transistor is damaged or leaking. It's pretty rare nowadays, but not unheard of. Also, sometimes overheating during soldering can affect it.

If it's a leaking transistor, it's possible to solve that with another resistor. I added R2 to the circuit to drain any leakage to the base of the transistor. It really shouldn't be necessary, but if it solves the problem then it's probably just a poor quality transistor.

It could definitely be something I did while soldering. I was really rusty with my soldering skills.

Being the lazy guy that I am, I think I will just put in a rocker swtich to the headlight.

kzmason wrote:

my '77KZ1000B has the on/off headlight switch on the RH control. What I want to do is eliminate that switch and get power to the headlight once the motor starts. I am no electrical guru, but I manage. I was thinking of a relay set up, but am not sure where to get the signal from. Stator? Regulator? Rectifier? help and suggestions, please?

Mmmm...you have the opposite need as I do. I have always hated the lack of of a headlight control switch on my 1979 SR650. My headlight is always on when the key is on. I MUCH prefer having control of when my light is on and off. This really would help if you have a weak battery when starting the bike.
So, if you decide to replace your switch housing, let me know. I've been looking for the older style housing with a switch since last year.