Wednesday, November 5, 2008

Project: Jameco Capacitance Adapter Kit

Once I bought all those random capacitors in a grab bag (Jameco part 163213 - Schwab's 3lb combination), I needed a way to quickly sort them out into values when some of them did not have any readable values on them (especially the small ceramic ones).

I solved that problem by buying the part #158001 kit for a adapter to measure capacitance on a normal DVM.

The kit included a PCB, and all of the parts needed to build it (except for the case). The kit is produced by Electronic Rainbow as part CA-1. It does its job well. Basically the circuit uses a 74HC132 a schmitt trigger quad two input NAND gate to create a pair of oscillators, and uses the unknown capacitance to alter the duty cycle of the PWM output to the DVM so it shows a different DC voltage proportional to the capacitance. Honestly, I am still not completely sure how it works.

The kit accomplished its purpose well - it gave me a chance to bone up on my soldering skills and build something that helped me sort some parts.

Now this pretty much just sits in a drawer. There really is not much need to measure unknown capacitors outside of my grab bag situation. When you buy them with known values it is not hard to keep track of them, and there is really not much sense in taking the time to desolder small capacitors for scrap boards because they are not that expensive.

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