Dynamo expert Qs
I’m running my dynohub with a shimano switch/current limiter which appears to be goosed (switches on and off intermittently, whether it is actually switched off or not!).
It seems a replacement is unavailable. Are limiters now integral with headlights?
I was also thinking of wiring up a capacitor for standlight at the back, but am guessing that any DIY attempt will not work as well as the commercially avaliable ones?Posted 5 years agofootflapsSubscriber
I know footflaps, but if it’s much more than a couple of components then I CBA and I may as well buy a better light as I’m just running a mudguard light at the mo.
My guess is you need four components:
A diode bridge rectifier (4 diodes in a module) to go ac to dc (assuming hub dynamo output is ac).
A zener diode as a clamp to limit the voltage, buy a beefy one and glue it to a heatsink.
A battery (NiMh or NiCd) in parallel with the lights.
A switch on the output to turn the lights off.
Possibly a capacitor to smooth the ac to dc, but I reckon you’d get away without it.Posted 5 years agoTheBrickMember
If you’re looking to limit the current you can use a simple current course you can use a jfet with the gate tide to the drain like this.Posted 5 years agorobdeanhoveMember
You could do a lot worse than look on pilom.com, Martin’s circuits are a great summary of a few neat ideas that should get you going, and some more complicated ones for the more ambitious:
It’s well worth a look on candlepowerforums too, once you have understood the basics
Happy tinkering. Oh, and you don’t need batteries, they’re nasty heavy things that need voltage regulation 😉Posted 5 years agojoemarshallMember
For a modern front light you don’t need regulation – it’s only for old lights that have bulbs, where they might blow. I think my b and m light instructions actually said not to fit any regulator. I’m guessing the same is true for rear.
If your regulator has the standlight built in, rather than it being in the rear light unit itself, that is a pain, probably easiest just to buy an led rear light with standlight built in, and maybe a modern front light while you’re at it (they are brilliant, you need one).
Alternatively, I have a home made dynamo rear without a standlight, and a cheap flashing light as a backup for junctions, which works fine. So standlight is not vital.Posted 5 years ago
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