DC/AC converter?

[micro_builder]

this may be an odd request, but does anyone know if there are DC/AC converters (inverters?) for rc applications? i can solder well enough, so if there's plans i could build my own if i needed too, but i've never seen DC/AC, only DC/DC. thanks for any info.

nick

[Miami Mike]

this may be an odd request...It's an unclear request. What exactly are you looking for?

[Rodney]

Most of your dc to dc converters first convert the dc to ac (a square wave) then step it up thru a transformer and rectify back to dc so you ought to be able to just tap off the ac (square wave) before it is converted back to dc.

[Andy W]

Most of your DC-DC convertors use extremely high switching frequencies iin the KHz range, not your typical low-frequency AC @ 50-60Hz.

Again, why do you need AC in an RC application?

[JMP_blackfoot]

It's explained in post #3 here :
http://www.rcgroups.com/forums/showthread.php?t=384467
The request seems to be for a bi-directional switch or ESC.

[Andy W]

Oh, well he's just talking about making his own version of a brushless ESC.
..a

[vintage1]

Of course the simple answer is a rotary converter. Couple a brushed motor to a brushless, put a battery on the brushed and pull 3 phase AC off the brushless ;)

[micro_builder]

thanks for the responses guys.

JMP Blackfoot found my other post in the micro forum:
i'm building an electromagnet, for an experiment in ornithopters. in order for it to do what i want it to do, it has to have an alternating current running through it to change the magnetic field between positive and negative as quickly as possible (but in a controllable way). using an DC to AC converter (inverter?) seemed the simplest way to achieve this, otherwise i'd be looking for a new controller of some sort that could "fake" an AC current in some way.

i've seen AC powered electromagnets that do exactly what i'm wanting, but they're huge, and heavy. i can scale down the magnet itself, but its the power flowing to it that i need to figure out how to do.

sorry if i'm not sounding very clear on what i'm wanting here, but thanks for the info, i'll see what i can do.

nick

[micro_builder]

thought a picture might help clear up what i'm trying to accomplish. hope it helps.

nick

[vintage1]

Oh. You want a magnetic actuator for a sort of 'galloping ghost' setup?

Thats a cinch. One of the easiest ways to do that is to get a one chip audio amplifier with a bridge style output - or a pair in a chip that can be bridged - and feed it with an ac signal at the right frequency.

Essentially regard your elecromagnets as a loudspeaker?

I am sure a PIC could generate the right sort of input waveform.

[micro_builder]

i like that idea. in the micro forum they were making suggestions on using an H-bridge and and a pic to controll it all. sounds like the same thing, almost sounds simple enough too. the speaker reference helps too, i was working off of the electromagnet i had at hand, which looks the same as the one in my drawing - the poles pointing out the same side. making just a coil with the magnet floating inside it might be easier, might give it a stronger magnetic field too. thanks vintage.

nick