2025 Component Abuse Challenge: Glowing Neon From A 9 V Relay

November 8, 2025 by Jenny List 7 Comments

Most of us know that a neon bulb requires a significant voltage to strike, in the region of 100 volts. There are plenty of circuits to make that voltage from a lower supply, should you wish to have that comforting glow of old, but perhaps one of the simplest comes from [meinsamayhun]. The neon is lit from a 9-volt battery, and the only other component is a relay.

What’s going on? It’s a simple mechanical version of a boost converter, with the relay wired as a buzzer. On each “off” cycle, the magnetic field in the coil collapses, and instead of being harvested by a diode as with a boost converter, it lights the neon. Presumably, the neon also saves the relay contacts from too much wear.

We like this project for its simplicity and for managing to do something useful without a semiconductor or vacuum tube in sight. It’s the very spirit of our 2025 Component Abuse Challenge, for which there is barely time to enter yourself if you have something in mind.

2025 Component Abuse Challenge: Pushing A 555 To The Limit

November 7, 2025 by Jenny List 5 Comments

The humble 555 timer has its origins back in the early 1970s as the NE555, a bipolar integrated circuit. Over the years it has spawned a range of derivatives, including dual versions, and ones using CMOS technology. Have these enhancements improved the performance of the chip significantly? [MagicWolfi] has been pushing the envelope in an effort to see just how fast an astable 555 can be.

The Microchip MIC1555 may be the newest of the bunch, a 5-pin CMOS SOT-23 which has lost the frequency control and discharge pins of the original. It’s scarcely less versatile though, and it’s a fine candidate for an oscillator to push. We see it at a range of values for the capacitor and resistor in an astable configuration, each of which is tested across the supply voltage range. It’s rated as having a maximum frequency of 5 MHz, but with a zero Ohm resistor and only the parasitic capacitance of an open circuit, it reaches the giddy heights of 9.75 MHz. If we’re honest we find this surprising, but on reflection the chip would never be a first choice for super-fast operation.

We like it that someone’s managed to tie in the 555 to the contest, and given that it still has a few days to run at the time of writing, we’re hoping some of you might be inspired to enter one of your own.

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

November 5, 2025 by Jenny List 20 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.

The Headache Of Fake 74LS Logic Chips

November 4, 2025 by Maya Posch 21 Comments

When you go on your favorite cheap online shopping platform and order a batch of 74LS logic ICs, what do you get? Most likely relabeled 74HC ICs, if the results of an AliExpress order by [More Fun Fixing It] on YouTube are anything to judge by. Despite the claims made by the somewhat suspect markings on the ICs, even the cheap component tester used immediately identified them as 74HC parts.

Why is this a problem, you might ask? Simply put, 74LS are Low-power Schottky chips using TTL logic levels, whereas 74HC are High-Speed CMOS, using CMOS logic levels. If these faked chips had used 74HCT, they would have been compatible with TTL logic levels, but with the TTL vs CMOS levels mismatch of 74HC, you are asking for trouble.

CMOS typically requires that high levels are at least 70% of Vcc, and low to be at most 30% of Vcc, whereas TTL high level is somewhere above 2.0V. 74HC also cannot drive its outputs as strongly as 74LS, which opens another can of potential issues. Meanwhile HCT can be substituted for LS, but with the same lower drive current, which may or may not be an issue.

Interestingly, when the AliExpress seller was contacted with these findings, a refund was issued practically immediately. This makes one wonder why exactly faked 74LS ICs are even being sold, when they’d most likely be stuffed into old home computers by presumably hardware enthusiasts with a modicum of skill and knowledge.

Continue reading “The Headache Of Fake 74LS Logic Chips” →

2025 Component Abuse Challenge: Weigh With A TL074

November 4, 2025 by Jenny List 19 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.

Regular Old Diodes Can Be More Photosensitive Than You Think

November 3, 2025 by Lewin Day 26 Comments

[Dhananjay Gadre] happened across a useful little trick the other day. Take any old 1N4148 or 1N914 glass-package signal diode and wire it up right, and you’ve got yourself a nifty little IR detector.

The trick is to treat the diode just like you would a proper IR photodiode. The part should be reverse biased with a resistor inline, and the signal taken from the anode side. Point an IR remote at your little diode and you’ll readily see the modulated signal pop up on a scope, clear as day.

The phenomenon is discussed at length over on Stack Exchange. Indeed, it’s a simple fact that most semiconductor devices are subject to some sort of photoelectric effect or another. It’s just that we stick the majority of them in opaque black packages so it never comes up in practice. In reality, things like photodiodes and phototransistors aren’t especially different from the regular parts—they’re just put in transparent packages and engineered and calibrated to give predictable responses when used in such a way.

Is this the way you’d go if your project needed an IR detector? Probably not—you’d be better served buying the specific parts you need from the outset. But, if you find yourself in a pinch, and you really need to detect some IR signals and all you’ve got on hand is glass-package signal diodes? Yeah, you can probably get it to work.

While this trick is well known to many oldheads, it’s often a lightbulb moment for many up-and-coming engineers and makers to realize this. Glass-packaged diodes aren’t the only light-sensitive parts out there, either. As we’ve explored previously, certain revisions of Raspberry Pi would reboot if exposed to a camera flash, while you can even use regular old LEDs as sensors if you’re so inclined. If you’ve got your own secret knowledge about how to repurpose regular components in weird ways, don’t hesitate to notify the tipsline!

2025 Component Abuse Challenge: The Opto Flasher

October 29, 2025 by Jenny List 6 Comments

There’s a part you’ll find in almost every mains powered switch mode power supply that might at first appear to have only one application. An optocoupler sits between the low voltage and the high voltage sides, providing a safely isolated feedback. Can it be used for anything else? [b.kainka] thinks so, and has proved it by making an optocoupler powered LED flasher.

If a part can be made to act as an amplifier with a gain greater than one, then it should also be possible to make it oscillate. We’re reminded of the old joke about it being very easy to make an oscillator except when you want to make one, but in this case when an optocoupler is wired up as an inverting amplifier with appropriate feedback, it will oscillate. In this case the rather large capacitor leading to a longish period, enough to flash an LED.

We like this circuit, combining as it does an unexpected use for a part, and a circuit in which the unusual choice might just be practical. It’s part of our 2025 Component Abuse Challenge, for which you just about still have time to make an entry yourself if you have one.