Sunday, April 06, 2008

Handy Dandy Electronics Calculators and Adventures in Theremin Design

For your reference, here are some Electronics calculators, just in case you don't want to do all that messy math-stuff.
LC Resonance Calculator
Air Core Inductor Calculator
Inductor Calculator
Toroid Calculator

In my adventures in Theremin Design, the LH and I went in the basement and began to plug random stuff into the Proto-board, just trying to get a nice sine wave from a fixed Colpitts oscillator. We didn't have too much luck; we had used the above calculators, figured out some values, but are having problems with the inductors. The coils we have pre-wound just were not "big" enough.

So I am winding a couple of coils this afternoon. We have a pair of these:
A-848032-2 MPP TOROID (this is a little donut of material called Molypermally. It's made of 79% nickel, 17% iron and 4% molybdenum alloy powder.)
The magnetic permeability of the material is 60 mu. The LH believes that 30 turns will give me 15 mH.

Yes, we calculated correctly. I wound some spare wire around the blue donut and we were good. But that was with a capacitor that is 1000 pF. However, the capacitance between a human hand and the Budgie antenna is not going to be very good -- so we decided to reduce the capacitance to 100 puff. That's going to take more like 60 turns. Soooo.... I'm winding. I am using some nice copper wire from a deflection yoke from an old TV set. Nothing like recycling.

Update #2:
They worked. It took 65 turns. One has a impedance of 112 mH and the other 116 mH. Yeah. Now I'm tired. I received a nice diagram from a reader -- I was going to play with transistors. But I didn't have the right ones. I may have to actually BUY something.

The project so far: two inductors.

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