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I have an AC generator of 6 VAC and 9 W power output. It is on an old bicycle motor, a BSA winged wheel. I intend to run NiceLite 3-6 VDC LED lights rated at 1 W each, one red and one white.

I appreciate I can use Schottky diodes to make a bridge rectifier to convert the AC. I also need the option of holding the energy charge into capacitors or batteries to give me stationary lights when the engine isn't running or I run out of fuel and end up cycling along at night time.

I realise I could use a switch to go between generated output and stored energy, but automatic switching employing the right transistor could be utilised.

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    \$\begingroup\$ Sounds like a reasonable plan, maybe not the best but it should be good enough. What are you having trouble with? (I can see one rough edge: when you rectify AC to feed a capacitor, the current goes in pulses which may cause the motor to vibrate a little. But it's good enough) \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Jan 20, 2023 at 13:17
  • \$\begingroup\$ When using a bridge rectifier to charge a capacitor, the old school solution was to use a choke. \$\endgroup\$
    – greybeard
    Commented Jan 20, 2023 at 15:47
  • \$\begingroup\$ When you said, "run out of fuel and end up cycling along at night time", you already eliminated capacitors. I get \$2\cdot \frac{\left(1\:\text{W}+1\:\text{W}\right)\,\cdot\, 1\:\text{hr}}{\left(6.2\:\text{V}\right)^2-\left(5.8\:\text{V}\right)^2}=3000\:\text{F}\$ meaning about 3000 Farads per hour of operation while 'cycling along'. You can see my assumptions, so adjust as necessary. But I think it's a battery. You already know a switch works. So the only question here is about an "automatic" switch. Which is what diodes do. Can you add more to the question? \$\endgroup\$
    – periblepsis
    Commented Jan 21, 2023 at 0:01
  • \$\begingroup\$ It is helpful to add a link to the "winged wheel". ridermagazine.com/2011/11/08/… You should also supply more details about your 6 VAC generator, such as output voltage vs speed, internal impedance, and frequency, for the range of speeds you expect. \$\endgroup\$
    – PStechPaul
    Commented Jan 21, 2023 at 0:56
  • \$\begingroup\$ More detailed info on the motor: classicmotorcycle.co.uk/bsa-cyclemotor And details on various bicycle generators (dynamos and alternators) sheldonbrown.com/generators.html \$\endgroup\$
    – PStechPaul
    Commented Jan 21, 2023 at 1:05

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Thanks for the information, I confirm the light coil of the ignition magneto doesn't give a frequency in the manual. Only 6V and 9W AC power to supply energy to 2 incandescent bulbs. A front light of 6W at 1A consumption and a rear light 0.5A at 3W. This is old School technology from the 1950's. With the advent of modern day electronics. It is hoped I can build a circuit incorporating 2 x 1W LED's. I understand that rectifying the AC input will give me a DC supply and that the power will drop by about 50%. The LED light diodes will be connected in parallel and energise between 3-6V DC, consuming 2W which leaves 2.5W spare energy. This could be used to charge Nicad batteries. Under full operating conditions the batteries would be fully charged and due to the light coil continuing to generate electricity. Would need further regulating. I therefore need a circuit diagram I can build into a circuit board. Given I am relative novice concerning circuit design.

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    \$\begingroup\$ Hi, This answer isn't clear to me. Either (a) You are writing it as an answer, because it's the final answer to your question. If so, please "accept" an answer (green "tick"), yours or another one (if posted) to close the whole question. Or (b) You are mistakenly writing this as an answer, when in fact you still want replies / help. In that case, this is an update, not an answer, and must be "edited into" your original question i.e. click "Edit" under the question, add this update, state what help is still needed, then delete this "answer". Which applies here, (a) or (b)? Thanks. \$\endgroup\$
    – SamGibson ♦
    Commented Jan 21, 2023 at 19:34
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    \$\begingroup\$ (As well as asking you to respond to the comment immediately above, I wonder if you are mistakenly using this site like a forum, without realising that it is a Q&A site. The HTML text entry form below labeled "Your Answer" is only to be used to write answers to the original question. I see you have not yet read the site tour where this is explained. Please read that and the help center to see the main site rules. Thanks.) \$\endgroup\$
    – SamGibson ♦
    Commented Jan 21, 2023 at 19:38

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