The schematic on the left and the assembled circuit on the right.

How To Make A Simple MOSFET Tester

Over on YouTube our hacker [VIP Love Secretary] shows us how to make a simple MOSFET tester.

This is a really neat, useful, elegant, and simple hack, but the video is kind of terrible. We found that the voice-over constantly saying “right?” and “look!” seriously drove us to distraction. But this is a circuit which you should know about so maybe do what we did and watch the video with subtitles on and audio off.

To use this circuit you install the MOSFET you want to test and then press with your finger the spare leg of each of two diodes; in the final build there are some metal touch pads attached to the diodes to facilitate this. One diode will turn the MOSFET off, the other diode will turn the MOSFET on, and the LED will show you which is which.

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Inside and outside the Contrib Cal.

Reify Your GitHub Commit History With Contrib Cal

Over on Instructables, [Logan Fouts] shows us the Contrib Cal GitHub desk gadget. This build will allow you to sport your recent GitHub commit activity on your wall or desk with an attractive diffuse light display backed by a 7×4 matrix of multicolor LEDs. Motivate yourself and impress your peers!

This humble project is at the same time multifaceted. You will build a case with 3D printing, make a diffuse screen by gluing and cutting, design a LED matrix PCB using KiCad, solder everything together, and then program it all with Python. The brains of the operation are a Raspberry Pi Zero W.

The Instructables article will run you through the required supplies, help you to print the case, explain how to solder the LEDs, tell how to install the heat-set inserts for high quality screw attachments, explain wiring and power, tell you about how to use the various screws, then tell you about where to get more info and the required software on GitHub: Contrib Cal v2.

Of course this diffuse LED matrix is only one way to display your GitHub progress, you can also Track Your GitHub Activity With This E-Ink Display.

Scott and his Prompt 80

Restoring A Vintage Intel Prompt 80 8080 Microcomputer Trainer

Over on his blog our hacker [Scott Baker] restores a Prompt 80, which was a development system for the 8-bit Intel 8080 CPU.

[Scott] acquired this broken trainer on eBay and then set about restoring it. The trainer provides I/O for programming, probing, and debugging an attached CPU. The first problem discovered when opening the case is that the CPU board is missing. The original board was an 80/10 but [Scott] ended up installing a newer 80/10A board he scored for fifty bucks. Later he upgraded to an 80/10B which increased the RAM and added a multimodule slot.

[Scott] has some luck fixing the failed power supply by recapping some of the smaller electrolytic capacitors which were showing high ESR. Once he had the board installed and the power supply functional he was able to input his first assembly program: a Cylon LED program! Making artistic use of the LEDs attached to the parallel port. You can see the results in the video embedded below.

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2025 One Hertz Challenge: Abstract Aircraft Sculpture Based On Lighting Regulations

The 2025 One Hertz Challenge is really heating up with all kinds of projects that do something once every second. [The Baiko] has given us a rather abstract entry that looks like a plane…if you squint at it under the right conditions.

It’s actually quite an amusing abstract build. If you’ve ever seen planes flying in the night sky, you’ve probably noticed they all have similar lights. Navigation lights, or position lights as they are known, consist of a red light on the left side and a green light on the right side. [The Baiko] assembled two such LEDs on a small sliver of glass along with an ATtiny85 microcontroller.

Powered by a coin cell, they effectively create a abstract representation of a plane in the night sky, paired with a flashing strobe that meets the requirements of the contest. [The Baiko] isn’t exactly sure of the total power draw, but notes it must be low given the circuit has run for weeks on a 30 mAh coin cell.

It’s an amusing piece of PCB art, though from at least one angle, it does appear the red LED might be on the wrong side to meet FAA regulations. Speculate on that in the comments.

In any case, we’ve had a few flashers submitted to the competition thus far, and you’ve got until August 19 to get your own entry in!

2025 One Hertz Challenge: Blinking An LED The Very Old Fashioned Way

Making an LED blink is usually achieved by interrupting its power supply, This can be achieved through any number of oscillator circuits, or even by means of a mechanical system and a switch. For the 2025 One Hertz Challenge though, [jeremy.geppert] has eschewed such means. Instead his LED is always on, and is made to flash by interrupting its light beam with a gap once a second.

This mechanical solution is achieved via a disk with a hole in it, rotating once a second. This is driven from a gear mounted on a 4.8 RPM geared synchronous motor, and the hack lies in getting those gears right. They’re laser cut from ply, from an SVG generated using an online gear designer. The large gear sits on the motor and the small gear on the back of the disk, which is mounted on a bearing. When powered up it spins at 60 RPM, and the LED flashes thus once a second.

We like this entry for its lateral thinking simplicity. The awesome 2025 One Hertz Challenge is still ongoing, so there is still plenty of time for you to join the fun!

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Dude about to pull a fire alarm

Fire Alarm Disco Party

What should your first instinct be when the room catches on fire? Maybe get out of the room, pull an alarm, and have a disco party? Not your first instinct? Well, this seemed pretty obvious to [Flying-Toast], who retrofitted an old fire alarm to activate a personal disco party.

After finding a fire alarm being sold on eBay, [Flying-Toast] couldn’t resist the urge to purchase one to use for his own purposes. He immediately gutted the life-saving internals to fill the shell with his own concoction of ESP goodness to be activated by the usual fire alarm mechanism. This sends a signal to the next elements of the party system.

Every part of the party system receives this activation signal, including the most important part, the party lights. Using a generic crystal disco ball and its own ESP, the party lights are more than sufficient to create the proper panic party. Of course, what is a party without music? With another ESP board and salvaged speakers, the proper atmosphere can be set right before the venue burns to the ground. The final touch is the additional hacked WIFI relays to turn off the lights in the room.

Priorities are important in emergencies, and that is exactly what [Flying-Toast] gave us with this project. Learning from this expertise is important, but how about learning from the near misses? For some risky decision making, be sure to check out the near nuclear war that was almost caused by a false alarm!

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Raspberry Pi Pico LED display sitting in window sill

An Ode To The Aesthetic Of Light In 1024 Pixels

Sometimes, brilliant perspectives need a bit of an introduction first, and this is clearly one. This video essay by [Cleggy] delivers what it promises: an ode to the aesthetic of light. But he goes further, materializing his way of viewing things into a beautiful physical build — and the full explanation of how to do it at home.

What’s outstanding here is not just the visual result, but the path to it. We’ve covered tons of different LED matrices, and while they’re all functional, their eventual purpose is left up to the builder, like coasters or earknobs. [Cleggy] provides both. He captured a vision in the streets and then built an LED matrix from scratch.

The matrix consists of 1024 hand-soldered diodes. They’re driven by a Raspberry Pi Pico and a symphony of square waves. It’s not exactly a WS2812 plug-and-play job. It’s engineered from the silicon up, with D-latches and demultiplexers orchestrating a mesmerizing grayscale visual.

Pulse-width modulation (PWM) is the secret ingredient of this hack. [Cleggy] dims each white pixel separately, by varying the duty cycle of its light signal. The grayscale video data, compressed into CSV files, is parsed line-by-line by the Pico, translating intensity values into shimmering time slices.

It transforms the way you see and perceive things. All that, with a 1000 LED monochrome display. Light shows are all highly personal, and each one is a little different. Some of them are really kid stuff.

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