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Test transistors, diodes, thyristors, resistors, capacitors and inductors. Also identify their leads and obtain their component value.

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Test transistors, diodes, thyristors, resistors, capacitors and inductors. Also identify their leads and obtain their component value.

When starting my journey into the world of electronics, I obtained a lot of parts by disassembling discarded electronic devices to salvage the individual components. One of the issues I had was identifying what some of the components were and whether they were any good. Even now, I still find it worthwhile to confirm the identity of the leads on transistors even on brand new ones.

There are many builds of component testers around and this is just one more of them. The software I used identifies most of the standard components; Resistors, Capacitors, Inductors, Diodes (and double diodes), Transistors, J-FETs, MOS-FETs, SCRs or Thyristors, Triacs. It failed to recognize Diacs, UJT's (interpreted as a double-diode) and Zener diodes (interpreted as a normal diode).

The circuit uses a Arduino Pro Mini and OLED screen.

When obtaining a Arduino Pro Mini, be aware of the different styles they come in.

In the picture above, I designed the PCB for the variant on the far right.

The Arduino Mini Pro is soldered onto the copper side of the board so as to reduce the size of the finished unit.

Printing of "Transistor Tester V2 - Case.stl" and "Transistor Tester V2 - Front.stl" are sliced using a 0.2mm layer height without any supports.

To print "Transistor Tester V2 - Text.stl", use a 0.2mm layer and switch to a contrasting filament at the start of layer 4.

Use glue or double sided tape to fix the Front and Text prints together.

I have included the Eagle files in case you want to get the board commercially made or do as I did and make it yourself. I used the Toner method.

Start by adding the links if your PCB is single-sided, resistors and the capacitor.

Next add the pin headers for the Arduino Pro Micro. Note there are two connections that go down to the PCB from where the FTDI pin header is normally connected (DTR and VCC). The actual FTDI pin header is along side and is mounted on the main PCB to reduce the overall height.

If you use a header on a single sided board, here is the method I use to add them.

Place header on PCB with longer pin side down, solder pins, push black plastic down towards the PCB.

Also add the right-angle 2 pin header for the switch connection and the JST socket for the battery connection.

Solder on the Arduino Mini Pro.

On the component side, add the 6mmx6mm tactile switch with a 6mm shaft, the 3 pin female machined header and the 3 pin right-angle Dupont header.

Glue a couple of supports for the OLED display. I used the plastic from a old pin header so that it matches the height of the pin header on the OLED display.

After the glue dries, solder on the OLED display.

Glue on the button top. Make sure the glue does not run down the shaft and into the switch.

Add the three 2mm Banana sockets. I used two 4mm washers on each socket. The bottom one had the wire soldered to it. Put a female Dupont connector on the other end and plug into the PCB.

Fix the PCB to the case using four M2 4mm screws.

Connect a FTDI programmer to the FTDI pin header.

In the Arduino IDE, select the settings as shown below and upload the sketch.

Finally add the battery and power switch and plug them into the PCB before closing the case.

The accuracy of this unit is not too bad. It is really good at identifying leads on transistors and that is what I will primarily use it for. I think it will make a useful addition to any toolbox.

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