easy way to generate an ac signal

[Andy Dingley]

des for use in light aircraft. Apparently flicking off one of the isolators= (battery I think) required in an aircraft would wreck the diodes in a conv= entional alternator.

Common on cars too. There are 9 diodes in a car alternator: 6 that carry t= he main output power, and 3 little ones to the regulator. If you suddenly i= solate the main diodes while the alternator is spinning with a field applie= d, then it's likely to try and pass the full load current through the sense= diodes.At which point they fry.

Still nothing to do with jump starting though.

[Bill Wright]

today is someday). I'll put it on the scope at work tomorrow.

You'll need to rotate the shaft to get any reading on the scope.

Bill

[Bill Wright]

The advantage of the hub ones is that you can just give the wheel a whizz and they keep running for quite a while, specially if you demonstrate momentum by putting weights on the spokes.

Bill

[Bill Wright]

You need to do your duty to humanity and tell the kids the truth (on the quiet).

Bill

[Clive George]

If you've got any load connected to the dynamo they slow it down quite well - they need a fair bit of mass to get over the force peaks.

[harry]

To generate 240 Watts would take quite a lot of effort. So you've got that wrong somewhere.

[harry]

????????????????

[harry]

he alternator,

his shed that you can modify to get the AC out.

d power one to spin the other. Or it to the back of a PC and run it from th= e fan in that.

But not a sine wave. They have been designe to produce as near a square wave as they can manage.

All rotating electric machine run on AC. All can be used as a "motor" or "generator".

[harry]

You are the one with your head UP your arse.

[harry]

They are covering their arses in case some half wit connects black to red.

[harry]

The battery isolator in light aircraft is so the battery can be swiftly cut off if there is an accident to prevent fire.

[harry]

Can you still get dynamos for bikes? I thought with these LED lights that batteries would last nearly forever.

[John Williamson]

harry wrote: I wrote:-

Agreed.

Brushless DC motors use electronics to generate the AC for the motor. As a result, unless you remove the electronics, you can't use them as generators, and turning them by external means has been known to blow the electronics. I'd not like to try to remove the electronics in a PC fan motor, as they're small and integrated into the motor itself.

[Man at B&Q]

Not if it's a DC motor.

REally, some of the suggestions in this thread are laughable.

MBQ

[Dave Plowman (News)]

[Man at B&Q]

the alternator,

n his shed that you can modify to get the AC out.

and power one to spin the other. Or it to the back of a PC and run it from = the fan in that.

More bollocks form Harry.

MBQ

[Dave Plowman (News)]

Irrelevant for this purpose.

Really?

[Dave Plowman (News)]

Whatever. If you disconnect the alternator from the battery with the engine running, there's a very good chance of damaging the alternator as the output volts can go sky high if there's little load. And that high voltage can kill diodes.

[The Other Mike]

Red isn't used that much for battery connections on cars today.

[The Other Mike]

Ask them to start collecting smoke detectors