Ideas on how to make a Propeller controlled VFO

bprager

I'm working on a project where I would like to vary the frequency of the 120V AC line from 60hz. I would need a range of about +- 15hz.

I like to use the propeller if possible so that the freq could be digitally controlled and selected, then shown on a small display.

Any ideas on the best way to approach this?

One way I've heard of is to generate a audio tone, feed it into a small audio amp and use a transformer to take the audio output and recreate 120V.

Not sure this is really the best way, or if there are modules that the propeller can easily interface to that would let me do what I need.

Any ideas would be very much appreciated!

Phil Pilgrim (PhiPi)

By "the 120V AC line", I assume you don't mean the 120V AC line. Changing its frequency would be impossible. So, first of all, how much current do you need at 120VAC? Does the 120VAC output have to be isolated from the Prop?

-Phil

bprager

Sorry, I should have posted that.

Yes, I don't intend to alter the incoming line, I want to generate an outgoing 120V signal that has variable frequency.

Power output would be around 10 watts or so. I would think that the 120V output would be isolated from the propeller, but its not a requirement.

Phil Pilgrim (PhiPi)

A class D, differential-output speaker amplifier driving a step-down transformer in reverse should do what you want. You would drive it with a filtered DUTY-mode counter output, programmed to produce sine waves.

-Phil