HackSpace magazine

Component testers: Direct from Shenzhen

By Ben Everard. Posted

Let’s be honest, dealing with electronics means dealing with lots of little things. These little things all have bits of information we need to know about them, but very little space on which to put it. Resistors have solved this problem by using a system of coloured bands that let you know the value and tolerance of a particular item, but not all components are quite this friendly.

What’s that transistor you have? If you’ve got good eyesight, you’ll be able to read the product code, but that doesn’t tell you much, unless you happen to know what it is. Even more difficult is knowing whether a component still works. If it’s charred, black, and smoking, then there’s a pretty good chance it’s now dead, but it’s often not easy to tell.

Fortunately, there are component testers to help us here. We picked up a ‘GM328 Mega328 Transistor Tester LCR Diode Capacitance ESR Voltage Frequency Meter PWM Square Wave Frequency Signal Generator’ from SeeSensor on AliExpress for £7.93, including UK delivery. It came without a power supply, but takes 7 to 12 V from a standard 2.1×5.5 mm power plug. It’s quite common to run these off 9 V batteries, and component testers typically have very low power usage, so batteries should last a very long time.

As you may guess from the name, this is built on the ATmega328P microcontroller – the same one found in the Arduino Uno. It’s likely that the firmware in this device is built on the open-source code originally created by Markus Frejek, and later adapted by others. This firmware has been used by many vendors over the years, and used in different form factors.

If you want to dive into the way these component testers work and find out more about the processes behind them, there is a great YouTube video on the subject from Andreas Spiess at hsmag.cc/runVun. It’s well worth a watch, as the process can seem a bit like magic (and it’s also a good way of learning a bit more about how microcontrollers work). There are also some details on the firmware website: hsmag.cc/QvayKT.

This particular device is built on a bare circuit board with a 160×128 LCD to display information, a zero insertion force (ZIF) connector for the component to be tested, and a rotary encoder to drive the interface. There are also screw connectors for the additional functions of frequency generation and PWM signal output.

The ZIF connector is split up into three sections labelled 1, 2, and 3. You just have to insert your component so that its legs are each in separate sections, and start it identifying. Having multiple options for each leg means that you don’t have to bend the legs too much to get them in – hopefully prolonging their life. If it recognises the component, it will quickly pop up with an answer as to what the component is, what its particular attributes are, and which leg is which. The ZIF connector can only work with through-hole components. There are also pads for placing on surface mount parts, though you have to be a bit careful about holding them in place while the testing runs.

While we found the component tester worked really well, we were less impressed with the frequency generator. There were only ten options (0–9 Hz). Perhaps you need a frequency in this range, but it’s not hugely useful. The PWM generator lets you set a percentage, and it will output the signal.

This could be useful for testing servos and other devices that take PWM input. It’s easy to use, with the menu-driven interface controlled by the rotary encoder, and that can be a really useful bit of workshop kit. The only real caveat is how much it adds, compared to the equipment you already have. Many multimeters can test for resistance and capacitance, and some have transistor testers. Few have quite the range of component testing that a dedicated unit does, but it will depend if the extra features are particularly worth it for you.

Overall, we expect this to have a permanent place on our electronics workbench. We’ve got oodles of components that we’ve brought for various projects over the years and had left over, and quite a few that have been used once or twice and probably still work, but are worth checking. We imagine that many of you are in a similar position, and this goes double for anyone working in a shared workshop.

A simple one-stop-shop for checking everything will make it much easier to reuse existing components, which makes building circuits a quicker, easier, and more environmentally friendly process, and that can only be a good thing.