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 Bruno |
Way to measure coil choke? |
Lead | |
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Posts: 2 (01/16/09 05:30:15) |
I found a few wound chokes in power supplies here at the shop over the years - I was wondering if anyone knew of a way to measure the value of them (the h
value). I realize it probably has to be done with a scope and a frequency generator - but anyone have any recommended sites that would explain the process?
Thanks Chris |
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desulfator2 |
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Posts: 979 (01/18/09 13:45:59) |
Simply purchase an LCR digital meter.
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Jay Q |
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Posts: 1 (01/18/09 14:25:52) |
Bruno, another way is use a sine generator and a resistor in series with the coil. Adjust the frequency so that the voltage across the coil is 3 dB down from
the generator. Calculate the inductance from L = R/(2*pi*F). Example: if r=100 ohms and the -3 dB frequency is 15.9 kHz, then L=.001 H. Be sure to include the
coil DC resistance in the R value.
Regards, Jay Q |
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H2O |
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Posts: 1 (01/18/09 15:00:27) |
Hi Chris
I came across these two sites that explains how to measure an unknown inductance, if one does not have LCR meter. Have not tried the process myself as I have just acquired a new DSO off 'eBay' last week and do not have frequency generator as yet. http://www.thekeeser.com/...e_an_unknown_inductor.htm http://www.sxlist.com/techref/inductor/measure.htm Regards John |
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Bruno |
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Posts: 3 (01/19/09 07:19:28) |
Thanks all, very helpful!
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AndyCraig |
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Posts: 1 (01/24/09 23:54:07) |
Simply purchase a desulfator. Then you won't need to measure the components.
Here's what worked for me and doesn't require a signal generator. Build the circuit mentioned above. It's insanely easy. Only two pages of theory/how-to and you can run with it: http://www.thekeeser.com/...e_an_unknown_inductor.htm Use your PC soundcard as a signal generator (get the freeware version) I didn't even need an amplifier: http://www.dr-jordan-design.de/signalgen.htm It worked for me. No more guessing about inductor values! Some tips: -I used an oscilloscope but I bet you a 'peak voltage detector' circuit, mentioned elsewhere in the forums, would do the trick. Maybe you can try for us & report back? -I used a 1uF non-polar capacitor. Considering the 20-20000 Hz range of your sound card, and targeting inductors in the 200-1000 uH range, that capacitor value is pretty good. You may not need non-polar. I did it just to be safe. A great source is from a computer power supply. There's often one right at the 120v AC input. -With Dr Jordan's software, I set the min/max freq at 20-20000 Hz and coarse mode. Click the slider to select it, then use left-right arrow keys on the keyboard. Once I've approached & gone past my peak measured voltage, come back to the freq that seems to be the peak, then switch to fine mode. Move in small increments for the precise frequency.
Last Edited By: AndyCraig
01/25/09 00:19:43.
Edited 2 times.
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AndyCraig |
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Posts: 2 (01/25/09 00:11:33) |
Try this peak detector & let us know how you fare. For the diode, almost any one will do. A 1N4148 comes to mind. For this peak detector's capacitor,
I'm not sure. Maybe a .1uF ? Don't make it too big or this circuit's DC output at Vout will be slow to rise or fall as you are fiddling around with
the frequency, trying to find the resonant frequency (and accompanying high peak voltage) of your inductor/capacitor circuit.
Vin is connected to the circuit you're measuring. Vout is to your volt-meter in DC volts mode. Expect as much as 3V from a non-amplified sound card. 
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Bruno |
Board Layout | ||
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Posts: 4 (02/02/09 17:31:30) |
Well, I finally figured out my choke coils, built the first desulphator to mixed success. I've experienced a major issue of ringing - so after some
research have decided to try making a new board. I'm working with PC Boards - because I have some, and like doing it the hard way. Does anyone have an
electronic copy of the board layout with a fixed scale? Chris
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AndyCraig |
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Posts: 3 (02/05/09 17:02:45) |
If you're building the Alastair Couper circuit, based on a P-channel FET, I think this may be it. You'll want to confirm since I just glanced.
Top level of that site seems to be here, if you want to look around some more. http://home.comcast.net/~...263/desulfator/desulf.htm |
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Bruno |
Fuzzy Peak | ||
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Posts: 5 (02/06/09 05:33:50) |
That's the circuit print I used. Unfortunately I didn't plan far enough ahead. I printed the circuit just fine, but started mounting my components on
the non printed side (like I normally would). Pin 0 of the LM555 ended up being on the + half of the board, not the - half. I had to bend the pins of the
timer over backwords so the timer would mount properly. Now my circuit seems to be working, but the wave doesn't have a nice clean peak - it's very
fuzzy showing a lot of noise and no clear peak - any suggestions on where to start debugging?
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emsvitil |
Measuring inductance. | ||
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Posts: 9 (02/09/09 01:55:26) |
Here's another way to measure inductance:
http://et.nmsu.edu/~etti/...ronics/induct/induct.html Use a simple transformer as the sinewave generator. Hook it up home power. Your frequency will be whatever you have (50/60Hz) |
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AndyCraig |
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Posts: 4 (03/05/09 18:47:11) |
It looks like you must use a 1.00 volt RMS source for the formula to work.
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emsvitil |
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Posts: 10 (03/06/09 03:19:54) |
Doesn't have to be 1 volt....
The math is easier with 1 volt, but it can be any voltage........ In last equation and source voltage = 1, x is voltage you've measured. When source voltage ^= 1 : x = (voltage measured/voltage source) |
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