zener diode help

that

on one of the alternator lines, take some voltage, half wave rectify it, (Personally would put a 1k resistor in series with the diode to protect if the cap or diode goes bad), put on a smoothing cap across a 10k? load resistor, measure the voltage across the load resistor via the circuit and adjust the trigger relay voltage to your low rev needs minus a few volts
https://www.ebay.co.uk/itm/DC-12V-24V-Control-Delay-Voltage-Detection-Upper-and-Lower-Voltage-Range-Switch/273015987889


A simpler circuit, but by the time you buy parts is probably more expensive than above, is the Half Wave Phase Control, and substitute the lamp for a relay and include a reverse polarity diode across the relay coil too. Possible problem is the fluctuating alternator supply voltage, will that relay oscilate due to the low revs? It is only powere by one source, rather than a battery. Ooops, nearly the same as #27
https://www.electronics-tutorials.ws/power/thyristor-circuit.html

polymaff

twhitehousescat wrote: »

1. Connect an similar rectifier arrangement with inputs in parallel with the alternator rectifier's inputs, and with its output connected to the headlight,

umm no thank you , I have ridden bikes that have had h/light powered only from coils on geni , basicly the lights go out at tickover

2. Break the feed from the alternator rectifier to all of the other circuitry,

is that reg /rect , the red wire that carries upto 120w at 12v and run direct to the battery that is the only circuit the reg/rect uses

1. If your alternator is that limited on tickover then your original idea will almost certainly suffer from relay dropout.


2. Ideally everything beyond the rectifiers as that will mean the regulator will compensate for the volt-drop across the added schottky diode. If your rectifier and regulator are in a sealed unit, then you'd have to settle for "everything else beyond the rectifier/regulator unit".

polymaff

twhitehousescat wrote: »

Can you expand these two into a single rigorous specification? Just what is to be the light's state in engine run, engine idle and engine off and the respective states of any switches that currently affect the light?

ignition in on position , light switch in on position , NO light until the engine is running , light to work even at tickover , ability o turn light on/off at will with engine running , using switch already fitted, the light is to be left in its state of wiring , which already used a relay to get full power

What do you want to happen under these circumstances?

1. engine is stopped because it stalled/failed/no fuel etc., and,
2. engine is stopped because I took expected action(s) to stop it.

and what would be those expected action(s)?

Don't feel that you need to follow this up, but the original idea, which I accept probably worked - once - is not a repeatable design. Just an accident - and definitely not an easy point to start from.

As has been demonstrated by all the other contributors to this thread.

twhitehousescat

1. engine is stopped because it stalled/failed/no fuel etc., and,
2. engine is stopped because I took expected action(s) to stop it.

the same to happen as many of millions of other bikes and scooters around the world , the sidelight and tail light would stay on , but h/light would go out until the engine was running again

this spec is used on the latest euro 4 bikes imported into the uk , and has indeed been a feature of bikes like the humble honda cg125 since start of manufacture back in the 80s

most small scooters and indeed the honda use ac h/lights

coffeehound

Is there a particular reason why no one’s suggesting full-wave rectification as the first stage? Would seem to solve one of the main problems with one 4-wire component.

twhitehousescat

yes but what voltage would we have in dc terms , we are talking max of 70ac here , and a floating ac (voltage) as well

techquest

coffeehound wrote: »

Is there a particular reason why no one’s suggesting full-wave rectification as the first stage? Would seem to solve one of the main problems with one 4-wire component.

Thought about that one too coffehound. Problem is there's so many suggestions now twitehousecats has forgotten what he was doing in the first place and he's going to need a sidecar addition to carry all the gear needed to work his simple lamp.

polymaff

twhitehousescat wrote: »

...I have ridden bikes that have had h/light powered only from coils on geni , basicly the lights go out at tickover

twhitehousescat wrote: »

...most small scooters and indeed the honda use ac h/lights

Are you implying that the latter all go out at tickover - but that you hope to go one better?

Heedtheadvice

I did not suggest full wave rectification as the original idea was to keep it as simple as possible.


The OP is struggling to implement a circuit based on single phase half wave rectification with a single diode andreservoir/smoothing capacitor......so how he would cope with a three phase full wave rectifier with six diodes is beyond comprehension. He/she after all is into mechanics not simple electronics and also has given valid reasons for discounting several suggestions that we should not ignore.


Unfortunately twhitehousescat is also giving invalid and/or illogical reasons for not going down some routes such as the potential high (in his/her opinion) alternator output voltage under certain conditions all suggesting, as as been written by the OP, a lack of understanding. If that is the situation it is all a non starter for building and testing/modifying any working circuit.


In that case and if their is forgetfulness to switch off the light when it ought to be off, then perhaps just fitting a big buzzer to warn is the best option!.....ah but then that also involves an understanding of how to sense that condition and wire into a buzzer! or an off the shelf or kit battery status monitor but then again....


If Twitehousescat wants to expand on what cannot be understood on my simple circuit I can guide to understand. ( I have already seen an error I have made in the connection of Zd2 and R1 but there is no point in correcting it if the circuit will not be used!).


Perhaps watching an idiots guide to making a battery status monitor/warning device connected into the lighting circuit might do the job such as described at https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=2ahUKEwiMxrTzy6fgAhXCjKQKHVeEB8wQtwIwC3oECAQQAQ&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D014CLJ98P1Q&usg=AOvVaw06FfL-IfiOZZNJlKE-3JVP


Otherwise I don't think I will contribute any more to what seem a fruitless end!

coffeehound

Heedtheadvice wrote: »

I did not suggest full wave rectification as the original idea was to keep it as simple as possible.


The OP is struggling to implement a circuit based on single phase half wave rectification with a single diode andreservoir/smoothing capacitor......so how he would cope with a three phase full wave rectifier with six diodes is beyond comprehension.

Well even a 3ph rectifier is a monolithic device which would be a tidy way to give DC plus a bit of ripple, which would negate the need for further smoothing components. But I was just meaning full-wave rectification of one phase, so straightforward to wire in. A standard 240-volt rms one would give a decent amount of headroom.

<snip> Otherwise I don't think I will contribute any more to what seem a fruitless end!

Kudos for your assistance this far, I lost sympathy halfway down page 1.