Nixie Gear Indicator Shines Bright

January 20, 2026 by Lewin Day 12 Comments

When you’re driving a car with a stickshift, it’s pretty easy to keep track of which gear you’re in. That can be a little bit more difficult on something like a motorcycle with a sequential shifter. [decogabry] built a neat gearshift indicator to solve this issue.

An ESP32 devboard is used as the brain of the build. It’s paired with an ELM327 dongle over Bluetooth, which is able to hook into the bike’s ODB diagnostic port to pick up data like engine RPM, wheel speed, and coolant temperature. The first two factors are combined in order to calculate the current gear, since the ratio between engine RPM and wheel speed is determined directly by the gear selection. The ESP32 then commands a Philips ZM1020 Nixie tube to display the gear, driving it via a small nest of MPSA42 transistors. A separate self-contained power supply module is used to take the bike’s 12 volt supply up to the 170 volts needed to run the tube. There is also a small four-digit display used to show status information, RPM, and engine temperature.

Notably, [decogabry] made this build rather flexible, to suit any bike it might be installed upon. The gear ratios are not hard coded in software. Instead, there is a simple learning routine that runs the first time the system is powered up, which compares RPM and wheel speed during a steady-state ride and saves the ratios to flash.

We’ve featured projects before that used different techniques to achieve similar ends. It’s also interesting to speculate as to whether there’s a motorcycle vintage enough to suit a Nixie display while still having an ODB interface on board as standard. Meanwhile, if you’re cooking up your own neat automotive builds, don’t hesitate to drop us a line.

Robot Sees Light With No CPU

January 19, 2026 by Al Williams 10 Comments

If you ever built a line following robot, you’ll be nostalgic about [Jeremy’s] light-seeking robot. It is a very simple build since there is no CPU and, therefore, also no software.

The trick, of course, is a pair of photo-sensitive resistors. A pair of motors turns the robot until one of the sensors detects light, then moves it forward.

Continue reading “Robot Sees Light With No CPU” →

Philips Kid’s Kit Revisited

January 14, 2026 by Al Williams 14 Comments

[Anthony Francis-Jones], like us, has a soft spot for the educational electronic kits from days gone by. In a recent video you can see below, he shows the insides of a Philips EE08 two-transistor radio kit. This is the same kit he built a few months ago (see the second video, below).

Electronics sure look different these days. No surface mount here or even printed circuit boards. The kit had paper cards to guide the construction since the kit could be made into different circuits.

Continue reading “Philips Kid’s Kit Revisited” →

Design Of Common Emitter Amplifier

January 11, 2026 by Al Williams 7 Comments

It used to be a rite of passage to be able to do the math necessary to design various bipolar transistor amplifier configurations. This doesn’t come up as often as it used to, but it is still a good skill to have, and [Void Electronics] walks us through a common emitter amplifier in a recent video you can see below.

The input design parameters are the gain and the collector voltage. You also have to pick a reasonable collector current within the range for your proposed device that provides enough power to the load. You also pick a quiescent voltage which, if you don’t have a good reason for picking a different value, will usually be half the supply voltage.

The calculations are approximate since the base-emitter voltage drop will vary by temperature, among other things. But, of course, real resistors won’t have the exact values you want, or even the exact value marked on them, so you need a little flexibility, anyway.

Continue reading “Design Of Common Emitter Amplifier” →

39C3: Hacking Washing Machines

December 29, 2025 by Elliot Williams 18 Comments

Many of us have them, few of us really hack on them: well, here we’re talking about large home appliances. [Severin von Wnuck-Lipinski] and [Hajo Noerenberg] were both working on washing machines, found each other, and formed a glorious cooperation that ended in the unholy union of German super-brands Miele and B/S/H — a Miele washer remote controlled by Siemens’ web app.

This talk, given at the 39th Chaos Communication Congress (39C3), is about much more than the stunt hack, however. In fact, we covered [Severin]’s work on the very clever, but proprietary, Miele Diagnostic Interface a little while ago. But now, he’s got it fully integrated into his home automation system. It’s a great hack, and you can implement it without even opening the box.

About halfway through the talk, [Hajo] takes over, dissecting the internal D-Bus communication protocol. Here, you have to open up the box, but then you get easy access to everything about the internal state of the machine. And D-Bus seems to be used in a wide range of B/S/H/ home appliances, so this overview should give you footing for your own experimentation on coffee machines or dishwashers as well. Of course, he wires up an ESP32 to the bus, and connects everything, at the lowest level, to his home automation system, but he also went the extra mile and wrote up a software stack to support it.

It’s a great talk, with equal parts humor and heroic hacking. If you’re thinking about expanding out your own home automation setup, or are even just curious about what goes on inside those machines these days, you should absolutely give it a watch.

Editor Note: The “S” is Siemens, which is Hackaday’s parent company’s parent company. Needless to say, they had nothing to do with this work or our reporting on it.

Retro Semiconductors: The Silicon Controlled Rectifier

December 28, 2025 by John Elliot V 9 Comments

Over on YouTube [Lockdown Electronics] reviews an old bit of kit known as the Silicon Controlled Rectifier (SCR). Invented in the 1950s the SCR is a type of thyristor and they were popular back in the 1970s. They are often replaced these days by the TRIAC and the MOSFET but you might still find some old schematics that call for them and you can still buy them.

The SCR is a three terminal electronic switch which latches on. You apply a signal at the gate which allows the other two pins, the anode and cathode, to conduct; and they continue to do so until power is removed. The silicon inside the device is comprised of three semiconductor junctions, as: PNPN. The P on the left is the anode, the N on the right is the cathode, and the P in the right middle is the gate.

Continue reading “Retro Semiconductors: The Silicon Controlled Rectifier” →

Drunken EBay Purchase Becomes Motorized, Speaking Dalek

December 26, 2025 by Donald Papp 11 Comments

Not every impulsive purchase on eBay leads to possession of a wooden Dalek, but when a friend did exactly that, [Tony Goacher] did his part to turn ‘Dalek Bob’ into a motorized and remote-controlled unit of impressive stature.

Fitting wheels to shafts and motors to a frame can be a bit tricky when none were made with the other in mind.

The purchased Dalek is made of wood and, with the help of two bolts, is of sufficient size to trap a human inside. There’s a bench of sorts upon which the captive can sit, and with some effort, shuffle the surrounding frame awkwardly about. The scale of the Dalek is impressive, but it was clear the effect of human-powered locomotion was lacking. The solution was to install wheelchair motors, tires, and an ESP32-based remote control.

Quite a lot of work went into mounting the motors and wheels, and the challenges will be familiar to anyone who has done hobby robotics. One can choose ideal motors and wheels, but making them fit one another can be an entirely different story. Shafts and hubs are of different sizes, motor mounting doesn’t quite match the platform, and it’s all a bit like fitting a square peg into a round hole. But with access to the right tools, it’s nothing a little metalwork and welding can’t solve.

For the control system, the ESP32 (with a beautiful CNC-routed custom PCB) sets itself up as a wireless access point that serves a web-based control panel for piloting, and controls two H-bridges to drive the motors. What’s more, it also provides a sound board from which a second operator can trigger appropriate phrases and sounds from the Dalek.

Some folks prefer their remote-controlled Daleks plush and cute instead of large and looming, but we like the smooth movement and imposing stature of this one. Watch it all in action in the video, embedded below.

Continue reading “Drunken EBay Purchase Becomes Motorized, Speaking Dalek” →