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Hi can any one help me please
I want to build an arduino based component identifier and tester like the ones you can buy from atlas
I want it to test resistors ,capacitors, diodes all types and transistors it should identify the component and it's pin outs as well as giving basic details of the component.
I know there are a few pic based ones out there but prefer to use an arduino if possable
If any one can point me in the right direction I would be great full

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The techniques use in a PIC-based component tester should work similarly in an Arduino-based tester.  I'd look for the source code of a PIC-based tester and study it until I understood how it worked.

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Some things you can do fairly easily:

1. Apply a known voltage,Vin, to 2 resistors in series, 1 known (R1) and 1 unknown (R2). Measure the voltage at the junction, Vout. Solve for R2:
Vout = Vin * R2/(R1 + R2)
Vout* R1/(Vin - Vout) = R2

2. Apply a known voltage to a known Resistor and unknown capacitor in series, with another known resistor from the junction to Gnd. Measure the voltage at capacitor, it will rise as the cap charges and finally stabilize. Turn off the known voltage (perhaps change the pinMode from output to input) and measure the decay time . Calculate from there.

3. Diodes - I think all you can do is tell its a diode and how much voltage drop it has, which side is anode/cathode. Apply known voltage to a known resistor in series with the diode to Gnd. Measure voltage at the junction. Will be with 5V (cathode connected to the resistor) or something like 0.3 to 0.7V (anode connected to the resistor. Might be able to get reading in reverse leakage current, if 10 bit resolution is good enough for that.

4. Transistors.  See grumpy_mike's BJT transistor tester.

5. Inductors - similar testing as for a cap. Should be able to find DC resistance, and inductance.


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