2025 Component Abuse Challenge: The Ever-Versatile Transistor As A Temperature Sensor

November 5, 2025 by Jenny List 11 Comments

One of the joys of writing up the entries for the 2025 Component Abuse Challenge has come in finding all the different alternative uses for the humble transistor. This building block of all modern electronics does a lot more than simply performing as a switch, for as [Aleksei Tertychnyi] tells us, it can also function as a temperature sensor.

How does this work? Simple enough, the base-emitter junction of a transistor can function as a diode, and like other diodes, it shows a roughly 0.2 volt per degree voltage shift with temperature (for a silicon transistor anyway). Taking a transistor and forward biasing the junction with a 33 K resistor, he can read the resulting voltage directly with an analogue to digital converter and derive a temperature reading.

The transistor features rarely as anything but a power device in the projects we bring you in 2025. Maybe you can find inspiration to experiment for yourself, and if you do, you still have a few days in which to make your own competition entry.

2025 Component Abuse Challenge: Weigh With A TL074

November 4, 2025 by Jenny List 17 Comments

The late and lamented [Bob Pease] was one of a select band of engineers, each of whose authority in the field of analogue integrated circuit design was at the peak of the art. So when he remarks on something in his books, it’s worth taking notice. It was just such an observation that caught the eye of [Trashtronic]; that the pressure on a precision op-amp from curing resin could be enough to change the device’s offset voltage. Could this property be used for something? The op-amp as a load cell was born!

The result is something of an op-amp torture device, resembling a small weighing machine with a couple of DIP-8 packages bearing the load. Surprisingly modest weights will change the offset voltage, though it was found that the value will drift over time.

This is clearly an experimental project and not a practical load cell, but it captures the essence of the 2025 Component Abuse Challenge of which it forms a part. Finding completely unexpected properties of components doesn’t always have to lead to useful results, and we’re glad someone had done this one just to find out whether or not it works. You still just about have time for an entry yourself if you fancy giving it a go.

2025 Component Abuse Challenge: A Piezo Disk Powers A Transmitter

November 2, 2025 by Jenny List 12 Comments

A piezo disk transducer is a handy part for reproducing beeps and boops, and can also function as a rudimentary microphone. Being a piezoelectric element, it can also generate usable power. Enough to run a radio transmitter? [b.kainka] is here to find out, with what may be the simplest possible transmitter circuit.

The active element in the circuit, such as it is, comes from a crystal. This functions as an extremely stable and high Q tuned circuit. When excited by a pulse of electricity, the circuit will carry oscillations in a similar manner to a bell ringing until the pulse is exhausted. A small lever fashioned from a piece of wire supplies the voltage by flexing the piezo disk and a contact, a diode discharges the reverse voltage as the disk returns to shape, and a small capacitor provides an AC path to ground. It works, if a small pulse of very low-power RF near the crystal’s frequency can be described as working.

It may not be the most practical transmitter, but it’s certainly something we’ve not seen before. It’s part of our 2025 Component Abuse Challenge, for which you still have time to make an entry yourself if you have one.

2025 Component Abuse Challenge: A Transistor As A Voltage Reference

November 1, 2025 by Jenny List 19 Comments

For our 2025 Component Abuse Challenge there have been a set of entries which merely use a component for a purpose it wasn’t quite intended, and another which push misuse of a part into definite abuse territory, which damages or fundamentally changes it. [Ken Yap]’s use of a transistor base-emitter junction as a voltage reference certainly fits into the latter category.

If you forward bias a base-emitter junction, it will behave as a diode, which could be used as a roughly 0.7 volt reference. But this project is far more fun than that, because it runs the junctions in reverse biased breakdown mode. Using one of those cheap grab bags of transistor seconds, he finds that devices of the same type maintain the same voltage, which for the NPN devices he has works out at 9.5 volts and the PNP at 6.5. We’re told it damages their operation as transistors, but with a grab bag, that’s not quite the issue.

We’ve got a few days left before the end of the contest, and we’re sure you can think of something worth entering. Why not give it a go!

Supercon 2025: Streaming Live

November 1, 2025 by Tom Nardi No comments

While we’d love to have you all join us in Pasadena, the next best thing is to connect up to the festivities through the magic of the Internet. As always, the main stage talks will be streamed live to our YouTube channel, while the talks taking place in the DesignLab will be recorded and posted afterwards.

Though it’s not quite as immersive as being in the alleyway and listening to the dogs bark (if you know, you know), you can also join the #supercon-chat channel in the official Hackaday Discord server if you want to virtually rub shoulders with some of our favorite people in the world.

Continue reading “Supercon 2025: Streaming Live” →

2025 Component Abuse Challenge: An Input Is Now An Output

October 31, 2025 by Jenny List 20 Comments

Part of setting up a microcontroller when writing a piece of firmware usually involves configuring its connections to the outside world. You define a mapping of physical pins to intenral peripherals to decide which is an input, output, analogue, or whatever other are available. In some cases though that choice isn’t available, and when you’ve used all the available output pins you’re done. But wait – can you use an input as an output? With [SCART VADER]’s lateral thinking, you can.

The whole thing takes advantage of the internal pull-up resistor that a microcontroller has among its internal kit of parts. Driving a transistor from an output pin usually requires a base resistor, so would it be possible to use the pullup as a base resistor? If the microcontroller can enable or disable the resistor on an input pin then yes it can, a transistor can be turned off and on with nary an output to be seen. In this case the chip is from ATmega parts bin so we’re not sure if the trick is possible on other manufacturers’ devices.

As part of our 2025 Component Abuse Challenge, this one embodies the finest principles of using a part in a way it was never intended to be used, and we love it. You’ve still got a few days to make an entry yourself at the time of writing this, so bring out your own hacks!

Supercon 2025 Badge Gets Vintage Star Trek Makeover

October 29, 2025 by Tom Nardi 3 Comments

There are still a few days before the doors open on this year’s Hackaday Supercon in Pasadena, but for the most dedicated attendees, the badge hacking has already begun…even if they don’t have a badge yet.

By referencing the design files we’ve published for this year’s Communicator badge, [Thomas Flummer] was able to produce this gorgeous 3D printed case that should be immediately recognizable to fans of the original Star Trek TV series.

Metal hinge pin? Brass inserts? Scotty would be proud.

Although the layout of this year’s badge is about as far from the slim outline of the iconic flip-up Trek communicator as you can get, [Thomas] managed to perfectly capture its overall style. By using the “Fuzzy Skin” setting in the slicer, he was even able to replicate the leather-like texture seen on the original prop.

Between that and the “chrome” trim, the finished product really nails everything Jadzia Dax loved about classic 23rd century designs. It’s not hard to imagine this could be some companion device to the original communicator that we just never got to see on screen.

While there’s no denying that the print quality on the antenna lid is exceptional, we’d really like to see that part replaced with an actual piece of brass mesh at some point. Luckily, [Thomas] has connected it to the body of the communicator with a removable metal hinge pin, so it should be easy enough to swap it out.

Considering the incredible panel of Star Trek artists that have been assembled for the Supercon 2025 keynote, we imagine this won’t be the last bit of Trek-themed hacking that we see this weekend — which is fine by us.