SparkFun Forums

[daemondust]

I know this doesn't quite fit here, but I don't know where else to ask.

I'm looking to measure the inductance of hand would inductors and transformers. I have a cheap 'scope for measurements and a uC I can use to output a square wave.

Does anyone know what circuits and formulae I can use to find the inductance in these?

Thanks

[riden]

I've seen a number of references to LC meters using PICs on the net. Google "inductance meter PIC". The basic principal is to create an oscillator with a known value of capacitance, an inductor, and the inductor you want to test. The resulting frequency is then measured by the PIC and converted into the inductance value. Conversely, if you have a known value of inductance, you have a capacitance meter using the same circuit.

To get you started, try this site. It has a good introduction and the formulas you desire.

[leon_heller]

http://www.amqrp.org/kits/elsie/index.html

I designed a simple PCB for the ELSIE 1, it works very well. You do need to be able to read Morse code. I've also done a PCB for the ELSIE 2 for AmQRP, but they never went ahead with the kit. That uses a display.

Leon

[OldCow]

This is off the subject.

Leon, did you use a LED to flash Morse code? A one-pixel GUI?

Here is a creasy idea. How about inventing a new code for Roman numbers? For example: a wink for I, a blink for V, a shimmer for X, etc. Thus 4 = wink-blink (IV), 7=blink-wink-wink (VII), 23=shimmer-shimmer-wink-wink-wink (XXIII), etc.

[riden]

Leon, did you use a LED to flash Morse code? A one-pixel GUI?

One nice thing about using Morse, fewer people will be in the position to borrow the meter! This reminded me of the strange comments I got when someone wanted to use my HP-45 (RPN vs algebraic notation). "Where is the = button?", they would say.

[daemondust]

This reminded me of the strange comments I got when someone wanted to use my HP-45 (RPN vs algebraic notation). "Where is the = button?", they would say.

I've had those reactions. The day of one of the tests in my physics class one of the other students forgot his calculator. The teacher offered him a slide rule, but he didn't know how to use it. I offered him my HP 48G since I didn't have a problem using a slide rule, but he decided to take his chances with what he had.

[leon_heller]

This is off the subject.

Leon, did you use a LED to flash Morse code? A one-pixel GUI?

Here is a creasy idea. How about inventing a new code for Roman numbers? For example: a wink for I, a blink for V, a shimmer for X, etc. Thus 4 = wink-blink (IV), 7=blink-wink-wink (VII), 23=shimmer-shimmer-wink-wink-wink (XXIII), etc.

It has a little speaker. A single 7 segment LED display is used on ELSIE 2, displaying the digits sequentially.

Leon

[wiml]

I eventually bought an LC meter from AADE. It does what it says on the box, I'm happy with it. Basically it's a PIC making a square wave etc...

[leon_heller]

I eventually bought an LC meter from AADE. It does what it says on the box, I'm happy with it. Basically it's a PIC making a square wave etc...

The ELSIE units work the same way, by measuring the change in frequency when the DUT is placed across an oscillator tuned circuit. The ability to measure very low values of C and L is very useful. They can even measure the package capacitance of crystals, just a few pF.

Leon