Lighting coil capacitor.

Hey electronics guys,

I was reading my “Basic Electronics” book tryna get smart enough to build my homemade temp. sensor.

Ran across a paragraph that says adding a capacitor to an AC circuit will make the light glow brighter.

Does that mean that just sticking a cap in line with the headlight on a stock moped would make the light brighter?

Are mopeds even AC? Or pulsed DC?

I feel like I should know this by now but I don’t.

Re: Lighting coil capacitor.

Probably Fred /

Most stock 6v Magneto’s like bosch and cev are AC and many systems use wiring and bulb wattage to regulate/balance voltage

No load the voltage goes to the moon and changing something can make a imbalance in circuitry

Re: Lighting coil capacitor.

Is it really alternating though?

Like, an alternator spins the coil of wires through the magnetic field. The sine wave goes positive and negative. Current goes both ways.

But mopeds are passing the magnet by the coil one way. So, I think the “wave” would be all above ground (viewed on oscope) just pulses of DC.

Please explain me how I’m wrong if that’s way off.

Re: Lighting coil capacitor.

> Papa _ Wrote:

> -------------------------------------------------------

> Is it really alternating though?


A magneto does not have a commutator , needed to produce direct current .

Re: Lighting coil capacitor.

6v magneto electrical systems are AC.

Check manufacturers owner manuals in their electrical system section and it will tell you the same.

Re: Lighting coil capacitor.


Humor me a second then cause I’m really stuck on this.

The magnet in the fly wheel goes one direction.

It passed over the coil and because of electronic PFM it causes the flow of electrons in the direction it is moving.

So, voltage on the line rises, peaks and drops back to zero until the magnet comes back around.

Where, in that system, can the flow of electrons reverse?

What am I missing?

Re: Lighting coil capacitor.

Dirty30 Dillon /

There are polar opposite magnets in the flywheel, it's not just one magnet. They're arranged + - + - around the inner perimeter

Re: Lighting coil capacitor.



Re: Lighting coil capacitor.

So, will a capacitor make the lights brighter?


Re: Lighting coil capacitor.

Not sure if a single cap would do any good .

A couple in the correct configuration with a couple of diodes would definitely make lights brighter .

Then there's the question of whether you want half wave or full wave current . ;)

Re: Lighting coil capacitor.

My book wasn’t trying to build a rectifier.

It says this:

It is evident that AC current does not really flow through a capacitor. It flows into the cap on the first alternation and charges the capacitor plates. Stored, it is returned to the circuit on the second alternation as the capacitor discharges.

So AC makes a lamp glow. AC circuit with a capacitor makes it brighter.

According to this teaching illustration. But maybe there’s a reason that isn’t what we see in the practical application of AC to light bulbs on mopeds?

Re: Lighting coil capacitor.

Dirty30 Dillon /

It's my understanding that while a capacitor won't work as an energy storage device in an AC circuit (as is charges and discharges with each cycle), it does function, albeit with reactance lag between the input and output, which is typically by 90*

While I've never tried this, but it look as if wiring a capacitor into the lighting circuit (and with this 90* reactance lag), you gain some brightness at idle (as the capacitor is remaining charged -- in either + or - -- after the input voltage reaches 0 on the sine wave), but I don't think it will make a difference at RPM's.

Again, this is just my theory based on my understanding of AC capacitor use. The only time I deal with caps in my professional work, it's DC.

But for a tiny bit more work, you can half/full wave rectify and not have to worry about it and just know that the capacitor WILL act like a battery and provide better output at idle.

Re: Lighting coil capacitor.

Cool thanks.

It was more a theory question that was bugging me. I’m not trying to get crazy bright lights.

Although, riding in the wilderness at night on a moped. Stopping at an intersection. Foggy, damp, moonlight barely coming through. Headlight basically just went out. Visor starts to fog up and you know you better pedal up to speed to get away from that El Chupacabra that’s about to snatch you off that moped.

I’m not scared of the dark for real. But moped headlights can be a little freaky if you are.

Re: Lighting coil capacitor.

🇮🇹💦 Of the Loin /

If you throw a diode and half rectify it into pulsed DC the capacitor will act as storage

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