Limiting voltage on Bicycle generator

[Menticol]

Hello guys!

I'm working again with my bicycle generator, driving an audio amplifier. But this time I removed the 12V SLA battery to gain a weight reduction. It was a great decision in terms of bike handling, but now I have two electrical problems I cannot get rid of:

1. Alternator whine.
I have used a full wave rectifier, and a big capacitor (10,000 uF) next to the amplifier. Almost imperceptible, but the problem persists. May I need a Choke coil?

2. Voltage limiting is lost.
Removing the battery allowed the voltage to reach 15V, so the amplifier sounds much better than before. But while riding downhill voltage may reach 20 or more volts, threatening the amplifier and my LM3915 bar display. Can you suggest me a way to limit the voltage, as shown in the (low budget) graphic?

Thank you so much!

 

[ronv]

Something like this might be the solution.

**broken link removed**

 

[MikeMl]

Or just use a low-dropout 12V or 15V linear regulator

 

[4pyros]

Limiting voltage on Bicycle generator will wast energy! Use a smaller battery to store the energy. Andy

 

[MikeMl]

Limiting voltage on Bicycle generator will wast energy! Use a smaller battery to store the energy. Andy

Not if he is pedaling uphill or into a headwind. The only time the energy is free is going downhill, or braking.

 

[4pyros]

Not if he is pedaling uphill or into a headwind. The only time the energy is free is going downhill, or braking.

Good point so I would put in a disconnect swicth to disconnect the generator from the battery for the uphills and run off battery untill you get to the top. Andy

 

[Menticol]

Thank you for your time guys!

Something like this might be the solution.

**broken link removed**

It's an awesome device Ronv. Unfortunately, importing products here tends to be tricky

Or just use a low-dropout 12V or 15V linear regulator ... The only time the energy is free is going downhill, or braking.

Looks like it's the only way to go. Now that you mention it, I tried attaching a rubber band around the generator shaft to reduce the RPM's during downhills. It worked but then, when the hill ended, reaching the minimum 12V was terribly harder.

Limiting voltage on Bicycle generator will wast energy! Use a smaller battery to store the energy. Andy

I can't Andy, because that continuous voltage would ruin the psychological goal of the project: No pedaling => No effort => You deserve no music

Attaching a 12V battery prevents me from reaching the glorious 15V. A 24V battery would be impossible to recharge with my setup.

Now, what do you think about the annoying whine? A choke coil would filter it?

 

[4pyros]

Now, what do you think about the annoying whine? A choke coil would filter it?

You can try chokes made for car radios to stop alternator whine. Andy

 

[Menticol]

Thank you Andy. What about this?

**broken link removed**

Maybe an overkill?

 

[4pyros]

Yes to big for a MP3 player thats what you are using right?

 

[Menticol]

Yes, the "head unit" is the mp3 player, but the amplifier are two obsolete IC's, rated 7,5W each. I'll try using a small nut as the choke core, and post the results.

Thank you so much by your advice Andy, Mike and Ronv

 

[4pyros]

here r some off the shelf ones;
Automotive Electrical, Engine Noise Filters | TESSCO 800 472 7373

But all you shold need to do is wrap some wire around a round core. Like this;

**broken link removed**

Andy