zener diode help

twhitehousescat

I do NOT want the light on with ign switch I ONLY want light on when engine is running

its wired to be switchable with ign on at the moment , it needs to have no power until engine is RUNNING and charging

that

here is a zener calculator http://www.calculatoredge.com/electronics/zener.htm

and that alternator delivers 35v ac, it has a peak around 50v

DoaM

Out of the box thought ... fit a manual switch for the headlight, and don't turn it on until the engine is running? If you're worried about headlight current through the switch, use the switch to turn on/off a relay and have the headlight powered through the relay contacts.

(The latter option is like your original design intent, except you're just using a switch from the battery to drive the relay rather than a zener circuit).

that

how about this as an idea

from https://www.electronics-tutorials.ws/power/diac.html

test at full revs, you need to make sure that the voltage across the relay is not too great. You ideally would want to shift the phase via the cap so that voltage that lags after the peak is used to get the maximum relay voltage and only to use the relay and not the series resistor
An scr could replace a triac
Possibly a 600A triac is a bit too big, expensive and hard to mount?
you need the circuit still to be energised at idle, otherwise you will stop at traffic lights and your main lights will die. So you need to know the alternators idle voltage

Very similar circuit to an old light dimmer.

could you not just put an extra relay on the starter to cut the lights when it is depressed?

Heedtheadvice

Having had a good sleep and thankfull for thats field control info...
I'll post a simple circuit on the lines of the original of the thread that ought to work, caters for the alt output voltage change, all simple components readily at cpc, will not make the relay chatter and fail prematurely, quick to energise when motor running and quick to switch off automatically.


Should meet the OP's requirement.....
......but still the slight concern raised by coffeehound of the lights going out on a stall! Time for an led bulb in the headlight?


In the meantime a bit of reading? https://www.electronics-tutorials.ws/diode/diode_5.html

Chino

that wrote: »

how about this as an idea

How about you explain why, for the OP's use case, it's better than the OP's original proposal?

twhitehousescat

Heedtheadvice wrote: »

Having had a good sleep and thankfull for thats field control info...
I'll post a simple circuit on the lines of the original of the thread that ought to work, caters for the alt output voltage change, all simple components readily at cpc, will not make the relay chatter and fail prematurely, quick to energise when motor running and quick to switch off automatically.


Should meet the OP's requirement.....
......but still the slight concern raised by coffeehound of the lights going out on a stall! Time for an led bulb in the headlight?


In the meantime a bit of reading? https://www.electronics-tutorials.ws/diode/diode_5.html

thank you

what others fail to remember , is that many many of the small honda,s on the roads of the world , including the cg125 sold by the billions , has its headlight powered/wired so that it only lights with engine running , as did royal enfields from 2001 - same problem as me , in 2001 they fitted starter motor (low crank syndrome)

Ps LED headlight bulbs are illegal on this bike , the bike has led side and tail fitted

that

Chino wrote: »

How about you explain why, for the OP's use case, it's better than the OP's original proposal?

if you use the zener calculation web site, with a 24v relay that approx consumes 65.6 ma (12v one comsumes about 100-160ma from ebay) for 36 volt supply which is rms. if the supply is 30-36 volts then guess it is workable.

If not enough voltage is generate the light may cut out, so freewheeling and yeild signs, plus easing off in traffic

We do not know the voltage range of the alternator from idle and max is 36v? rms
The circuit alone could consume over 30w, that resistor will get hot.


in my mind taking a slice of the voltage phase is a better way. Possibly connecting to the rev output is still better?

Cornucopia

I think most of us that dabble (or even work professionally) with electronics would probably want to experiment around a new working environment like this to see what works best. There are probably hundreds of different workable solutions.

I suggest some form of isolation between the two halves of the circuit, and also a slightly more complex design to address the power considerations above.

I am not a designer of analog circuitry, but this would be my effort:-



The idea is that the internal LED within the Optoisolator would consume only a few milliamps, and the variable resistor (say 68K) would enable it to be adjusted to suit the voltages actually present from the alternator. With experimentation, it might be possible to determine values for the Capacitor and 10K Resistor that would enable direct connection to the alternator without the optoisolator.

For a small relay, a general purpose transistor like the BC548 would be fine. For a bigger relay, something with greater power might be required.

twhitehousescat

thanks , and i am after a very simple setup with as little components needed , that would stand abuse on a motorcycle