While pulling together parts for my various desulfator builds, I have come across the need to test/measure the values of some Inductors and Capacitors that I have in my parts drawers. On a previous occasion I had purchased (from eBay) an LCR meter which gives at least some information (inductance, capacitance, and resistance). It doesn't measure the ESR value of capacitors however. I went looking around for a similar meter that would measure ESR and instead ran across the following circuit that does everything above and then some. I have seen other members mention in these message boards that they were waiting for meters to be delivered before being able to test their parts. I submit this post as a potentially faster/cheaper way to get a 'good enough' measurement of your parts. Hopefully it is ok to post this even though it isn't directly related to desulfating.
Anyway, without further ado... the original circuit is the 'Transistor Tester' circuit by Markus Frejek posted at the following (German) site:
The original circuit boasts the following features:
- Automatic detection of NPN and PNP transistors, N-and P-channel MOSFETs, diodes (including double diodes), thyristors, triacs and resistors and capacitors.
- Automatic calculation and display of the pins of the component under test
- Detection and display of protection diodes for transistors and MOSFETs
- Determination of the gain and the base-emitter forward voltage at transistors
- Measuring the gate threshold voltage and gate capacitance of MOSFET
- Display the values on a text LCD (2 * 16 characters)
- Less than 2 second (except for larger capacitors) duration of a component testing
- One-button (or less) operation, (optional) automatic shutdown
- Power consumption when switched off: <20 nA
The original circuit is pretty simple and consists of a small number of parts:
- an ATMEGA8 (i.e. arduino) with power circuitry (i.e. 78L05 voltage regulator) and (optional) shutdown circuitry
- a 16x2 (or larger) HD44780 based character LCD
- an (optional) button (for initiating component tests)
- a few resistors, and other misc. parts
The firmware was picked up and further modified by Karl-Heinz Kubbeler. Very recently it gained the following additional features:
- Self calibration process to improve accuracy
- Measure inductance from about 0.01mH to 20H
- Measure ESR (for > 2 uH capacitors) with a resolution of about 0.01 ohms
These are the features that I really wanted. To enable these features you do have to have at least a 16 KB ATMEGA (i.e. ATMEGA168(p) or ATMEGA328(p)).
There is more information at the following link on the same (German) site:
I was able to quickly build this circuit, first on a protoboard, and then on a piece of stripboard, and can verify that it seems to work amazingly well.
I will post my build details next / below...