Lighting coil issue, help me please

[Starky307]

I've just tried fitting a lighting coil (alternator) to my KXF250.

The output from the alternator goes to a rectifier, it then goes through a diode to a battery, just before the diode it feeds a coil (for the headlight contact). The battery (down stream of the diode) goes through the contact (of the coil) and then to the headlight and back to a common negative on the coil.

It won't bring the coil in but it will charge the battery, there appears to be no potential across the coil (which is the dc output of the rectifier before the diode supplying the battery).

When the bike runs the voltage across the battery increases so the coil output is working.

The idea is for the lights to only work when the bike is running without the need for a switch.

Any ideas what wrong?

[CookMySock]

Hokay.

Is this a single phase or three phase stator ? Can you post a wiring diagram?

What do you mean "coil" ? Do you mean a coil of a relay? Do you have a test meter or test lamp? Take some measurements across the relay coil and tell us what you see.

Try placing a small bulb in line with the relay and see if it lights up a wee bit.


Steve

[Starky307]

Hokay.

Is this a single phase or three phase stator ? Can you post a wiring diagram?

What do you mean "coil" ? Do you mean a coil of a relay? Do you have a test meter or test lamp? Take some measurements across the relay coil and tell us what you see.

Try placing a small bulb in line with the relay and see if it lights up a wee bit.


Steve

Single phase, unable to sketch or scan a wiring diagram on my apple mac book. I mean a relay coil, yes to meter and lamp.
Across the relay coil is the resistance of the coil, I'll need to measure it tonight as I can't remember what it was.

I'll try putting the test lamp in series with the relay coil tonight and see what happens, I'm not thinking much will happen as the voltage measured between those points last night appears to only be the difference between the battery voltage and the rectifier output. By this I mean at idle there is 0 volts and at high revs it gets to about 1.5 - 2 Volts dc, so i would guess with a lamp in series it would not go and then at high revs it would be very dim.

I'll try and sort out a wiring diagram of what I have done.

[Starky307]

Picture added, please excuse the quality as I tried to draw using a free ware version of photoshop. I think you'll get the idea.

[CookMySock]

Ok you are sort-of on the right track. I just wonder if the layout is slightly wrong. Will need to see a sketch I think.

Steve

[paturoa]

Can you label your diagram with letters and then tell us what the voltages are using those references.

Also set your meter to AC volts and do the same.

Are you sure that it is just a rectifier? Could be a regulator, still have to wonder why the diode is in circuit unless the intent is to use as a switch to stop the light when the engine is off.

If you are absolutely sure that its just a rectifier, also test the voltages without the battery connected, but don't rev it too much or you might blow the bulb.

Edit - can you also draw if there is a switch for the relay. Edit x2 - re-read first post Duh!

[bogan]

diagram layout looks good as to me. Those voltage figures suggest you may have got some wires hooked up a bit wrong perhaps? sure +ve of coil is to rectifier positive output, and -ve of coil is to ground?

[bogan]

Can you label your diagram with letters and then tell us what the voltages are using those references.

Also set your meter to AC volts and do the same.

Are you sure that it is just a rectifier? Could be a regulator, still have to wonder why the diode is in circuit.

If you are absolutely sure that its just a rectifier, also test the voltages without the battery connected.

Edit - can you also draw where the switch is for the relay.

if i understand correctly, the diode is the switch for the headlight coil, ie it stops the battery from operating the headlight coil, and when running power from the alternator/rectifier activates the lighting coil, a smart and simple idea

[CookMySock]

if i understand correctly, the diode is the switch for the headlight coil, ie it stops the battery from operating the headlight coil, and when running power from the alternator/rectifier activates the lighting coil, a smart and simple idea

On the face of it, thats a good idea, but it will drop 0.6V from the battery state, quite likely removing as much as 30% charge from the battery.

I'm surprised that doesn't work though. I would test the relay to make sure its ok. Take a voltage measurement right across the relay. Also, perhaps you have the relay wired incorrectly.

If none o that works, try removing the diode and wiring the output of the rectifier directly to the battery, and then connecting the relay coil straight across the AC output of the stator.

edit: you might be able to use the diode to rectify the stator directly to the relay coil, but the relay coil should work from AC I would have thought. The half wave rectification the diode will provide will not provide much power to the relay coil so try with and without it.

Steve

[bogan]

On the face of it, thats a good idea, but it will drop 0.6V from the battery state, quite likely removing as much as 30% charge from the battery.

good point, unless he uses a schottky diode then itll only be .15V

[Starky307]

Can you label your diagram with letters and then tell us what the voltages are using those references.

Also set your meter to AC volts and do the same.

Are you sure that it is just a rectifier? Could be a regulator, still have to wonder why the diode is in circuit unless the intent is to use as a switch to stop the light when the engine is off.

If you are absolutely sure that its just a rectifier, also test the voltages without the battery connected, but don't rev it too much or you might blow the bulb.

Edit - can you also draw if there is a switch for the relay. Edit x2 - re-read first post Duh!

It's a regulator rectifier all together.

I'll try and do the drawing with reference voltages.

if i understand correctly, the diode is the switch for the headlight coil, ie it stops the battery from operating the headlight coil, and when running power from the alternator/rectifier activates the lighting coil, a smart and simple idea

That is exactly what I wanted to happen, just like the klx 450 does, no light switch, light only works when the engine runs.

On the face of it, thats a good idea, but it will drop 0.6V from the battery state, quite likely removing as much as 30% charge from the battery.

I'm surprised that doesn't work though. I would test the relay to make sure its ok. Take a voltage measurement right across the relay. Also, perhaps you have the relay wired incorrectly.

If none o that works, try removing the diode and wiring the output of the rectifier directly to the battery, and then connecting the relay coil straight across the AC output of the stator.

edit: you might be able to use the diode to rectify the stator directly to the relay coil, but the relay coil should work from AC I would have thought. The half wave rectification the diode will provide will not provide much power to the relay coil so try with and without it.

Steve

Battery voltage increases to between 13.5 and 14 volts dc with half or more throtle, drops back to 12.5 when no engine running.

I get no voltage (dc) measurement across the relay (I would expect the same voltage here as the battery when engine running) but then it will sometimes be the voltage difference between the battery without the engine running and the battery with the engine running.

Relay works, as the system works on the bench or if I short out the diode (back feeding from the battery).

The ac output is unclipped prior to the regulator/rectifier so I don't want to put it to the relay coil.

good point, unless he uses a schottky diode then itll only be .15V

I've tried two diodes and both the same result, they are fine as I have measured them and they are around the 0.567 v breakover, what I would expect them to be.


Keep the ideas coming

[Starky307]

All these measurement are from memory and with the bike running.
First letter is the positive lead

B-A 0 to 1.5 volts dc (depending on throttle position)
C-A 12.5 to 13.5 volt dc (depending on throttle position)
A=D
E-F 13-14.5 volts AC RMS
H-A = C-A

That is as much as I can remember.

I'm off to have another go at it so i'll try and bring back some more exact readings

[bogan]

one thing is maybe the stator/rectifier cant supply enough current to turn the relay on, though this seems very unlikely as it can supply enough current to power the headlight, it would only be if the voltage coming from the rectifier is unregulated, ie just a rectified half ac waveform. In this case the coils inductance woul provide significant impedance and there would not be enough current to switch the relay. A solution to this would be to put a large capacitor between A and B.

A quick test to check whether it is the power supply would be too clip a 12V source (other battery, or battery charger) to A and B, if relay clicks and lights come on then you have a power supply issue, may be able to fix it with a cap as above.

[Starky307]

one thing is maybe the stator/rectifier cant supply enough current to turn the relay on, though this seems very unlikely as it can supply enough current to power the headlight, it would only be if the voltage coming from the rectifier is unregulated, ie just a rectified half ac waveform. In this case the coils inductance woul provide significant impedance and there would not be enough current to switch the relay. A solution to this would be to put a large capacitor between A and B.

A quick test to check whether it is the power supply would be too clip a 12V source (other battery, or battery charger) to A and B, if relay clicks and lights come on then you have a power supply issue, may be able to fix it with a cap as above.

If I put another 12v source on A and B the lights come on.

I think the capacitor trick is what I am missing to bring the relay coil on.
Back to the shed to see what I can dig up.

I remember that instead of a battery I could of used a capacitor with the DC system instead of the battery, I just didn't know what capacitance to use or where to get one from bigger enough.

All this so I could use the trick LED tail light, should have just run the normal regulated output and had an AC headlight...

[CookMySock]

B-A 0 to 1.5 volts dc (depending on throttle position)
C-A 12.5 to 13.5 volt dc (depending on throttle position)

That description is infeasible. You have an error somewhere.

E-F 13-14.5 volts AC RMS
H-A = C-A

That is as much as I can remember.

I'm off to have another go at it so i'll try and bring back some more exact readings

Uh huh.

I think either the diagram you have drawn is not what you actually have, or else you have a fault in the circuit. Give all the connections the yank test and see if they fail.

You are on the right track though. What you have drawn should work.

Steve