Thanks. rq3!Unless the frequency is changing rapidly, a simple RC filter, droppng resistor, and two ADC readings should get what you want from any Picaxe.
The frequency is not changing at all so this "should" work.
Here's the story behind the magnetic bed.
My wife's sister discovered a man on the east coast of Florida who invented a magnetic bed that, he said, could cure many diseases. She traveled from South Carolina to visit this guy and asked my wife to join her to get some "treatments".
Unimpressed by his claims but curious, we chauffeured them over to a hole-in-the-wall clinic about 120 miles from our home.
He said he didn't charge but only took donations to keep out of trouble with the law.
The "bed" was a leather couch about 3 inches thick connected by a cable to a control box. After my wife was comfortable, he energized the machine. Handing me a neodymium magnet, he instructed me to hold it in my palm and and pass it over my wife's body. Even at 18 inches above the bed surface I could still feel the magnet vibrating! After a 45-minute treatment we headed for home. My wife felt that the bed did her some good, so we returned the next week and stayed overnight for two more treatments.
Motels, meals, fuel, and a donation was getting expensive.
Time to head to the lab and do some experimenting.
Pumping 5 amps through an auto relay got our Harbor Freight neodymium magnet vibrating nicely 12 inches away, for perhaps 20 seconds, before the Magic Smoke appeared! Success!!
Needing bigger coils that could handle the current, we constructed the ones we are now using.
We're saving a bundle not driving to the East Coast every week and now I've become the family hero!