LED Probe: A Smart, Simple Solution For Testing LEDs

June 14, 2025 by Matt Varian 13 Comments

If you’ve worked on a project with small LEDs, you know the frustration of determining their polarity. This ingenious LED Probe from [David] packs a lot of useful features into a simple, easy-to-implement circuit.

Most multimeters have a diode test function that can be used to check LEDs; however, this goes a step further. Not only will the probe light up an LED, it will light up no matter which side of the LED the leads are touching. A Red/Green LED on the probe will indicate if the probe tip is on the anode or cathode.

The probe is powered by a single CR2032 battery, and you may notice there’s no on/off switch. That’s because the probe enters a very low-current sleep mode between uses. The testing intelligence is handled by either an ATtiny85 or, in the newest version, an ATtiny202, though the basic concept and design are compatible with several other chips. All the design files for the PCB, the ATtiny code, a parts list, and a detailed explanation of how it works are available on [David]’s site, so be sure to check them out. Once you build one of these probes, you’ll want something to test it on, so explore some of the LED projects we’ve featured in the past.

2025 Pet Hacks Contest: Cat At The Door

June 12, 2025 by Matt Varian 14 Comments

This Pet Hacks Contest entry from [Andrea] opens the door to a great collaboration of sensors to solve a problem. The Cat At The Door project’s name is a bit of a giveaway to its purpose, but this project has something for everyone, from radar to e-ink, LoRa to 3D printing. He wanted a sensor to watch the door his cats frequent and when one of his cats were detected have an alert sent to where he is in the house

There are several ways you can detect a cat, in this project [Andrea] went with mmWave radar, and this is ideal for sensing a cat as it allows the sensor to sit protected inside, it works day or night, and it doesn’t stop working should the cat stand still. In his project log he has a chapter going into what he did to dial in the settings on the LD2410C radar board.

How do you know if you’re detecting your cat, some other cat, a large squirrel, or a small child? It helps if you first give your cats a MAC address, in the form of a BLE tag. Once the radar detects presence of a suspected cat, the ESP32-S3 starts looking over Bluetooth, and if a known tag is found it will identify which cat or cats are outside waiting.

Once the known cat has been identified, it’s time to notify [Andrea] that his cat is waiting for his door opening abilities. To do this he selected an ESP32 board that includes a SX1262 LoRa module for communicating with the portable notification device. This battery powered device has a low power e-paper display showing you which cat, as well as an audio buzzer to help alert you.

To read more details about this project head over to the GitHub page to check out all the details. Including a very impressive 80 page step-by-step guide showing you step by step how to make your own. Also, be sure to check out the other entries into the 2025 Pet Hacks Contest.

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Bringing A Father Ted Joke To Life

June 8, 2025 by Matt Varian 8 Comments

Inspired by a gag from a mid-90s sitcom Father Ted, [Stephen] decided to create his own talking tape dispenser.

This project is a actually a follow-up to the first version of the dispenser he built back in 2022, and [Stephen] has documented the process thoroughly for anyone wanting to build their own. In the first version, he modified a tape dispenser to house a Raspberry Pi, enabling voice functionality. In the new version, he replaced the Raspberry Pi with a cheaper ESP8266 and designed an entirely 3D printed dispenser that looks closer to the screen-used version.

A clever change was replacing the rotary encoder with a custom encoder embedded in the printed parts. Using a photodiode and an LED, it measures the tape pulled from the spool. As you pull the tape, the encoder calculates the length and announces it through the speaker, just like in the show.

If you’re into prop recreations like this, be sure to check out the winners of our 2022 Sci-Fi Contest.

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Solder Stencil Done Three Ways

June 6, 2025 by Matt Varian 30 Comments

This project, sent in by [Henk], goes through a few different ways to make a solder stencil using a vinyl cutter, a CO2 laser, and a fiber laser.

The project starts with identifying a method to convert the board’s Gerber files to a PNG, which is ultimately used to create a vector file for use with the laser. The first stencil, made with the CO2 laser, was cut out of masking tape. This worked fine for larger cutouts and is certainly a cheap option if you don’t have too many small components. A slightly better approach with the CO2 laser was using vinyl sheet release paper, which seemed to hold together better than the tape.

Laser-cut masking tape works, but not for long.

A vinyl cutter was also used as an experiment, but it didn’t perform as well as the CO2 laser, as expected, since the cutter uses a knife rather than light, leading to some tearing issues.

The final method utilized a fiber laser and an empty drink can to create a metal stencil. First, the can had to be cut open, heated, and flattened. The fiber laser was able to cut clean footprints in the aluminum, creating a stencil that would hold up to more use than the paper variations.

The finale of this exploration into laser stencil making was using the fiber laser to solder the board together. The stencil was used to spread paste on the pads, parts were placed on the board, and then the fiber laser heated the solder paste to solder them to the board. The board looked a bit toasty afterwards, but we imagine the process could be fine-tuned to reduce the collateral damage a bit.

Once you’ve got your stencil ready to go, you can combine it with a 3D printed jig to hold the PCB while you apply the solder paste.

From Burnt To Brilliant: A Toaster’s Makeover

May 28, 2025 by Matt Varian 26 Comments

Appliances fail, but that doesn’t mean it’s the end for them. This impressive hack from [solopilot] shows the results possible when not just fixing but also improving upon its original form. The toaster’s failed function selector switch presented an opportunity to add smart features to the function selection and refine control over its various settings.

Before upgrading the toaster, [solopilot] first had to access its components, which is no trivial task with many modern appliances. Photos document his process of diving into the toaster, exposing all the internals to enable the upgrade. Once everything was accessible, some reverse engineering was required to understand how the failed function selector controlled the half-dozen devices it was wired to.

Next came the plan for the upgrades—a long list that included precise temperature control and the ability to send an SMS showing the state of your meal. A Raspberry Pi Zero, a solid-state relay, a relay control board, and a thermocouple were added to the toaster, unlocking far more capability and control than it had originally. Some tuning is required to fully enable these new features and to dial in the precision this once run-of-the-mill toaster is now capable of.

The work wasn’t limited to the toaster itself. [solopilot] also seized the opportunity to create an Android app with speech recognition to control his now one-of-a-kind Cuisinart. It’s probably safe to say his TOA-60 is currently the smartest toaster in the world. If you check out his documentation, you’ll find all the pinouts, circuits, code, and logic explanations needed to add serious improvements to your own toaster. We’ve featured several other toaster oven projects over the years, most of which have focused on turning them into reflow ovens, so it’s exciting to see one aimed at improving upon its original design.

2025 Pet Hacks Contest: Fytó – Turn Your Plant Into A Pet

May 27, 2025 by Matt Varian 2 Comments

This entry into the 2025 Pet Hacks Contest is about bringing some fun feedback to normally silent plants. Fytó integrates sensors and displays into a 3D printed planter. The sensors read the various environmental and soil conditions that the plant is experiencing, and give you feedback about them via a series of playful expressive faces that are displayed on the screen embedded in the planter.

At the core of the Fytó is a Raspberry Pi Zero 2 W, which has plenty of power to display the animations while also being small enough to easily fit inside the planter without it growing in size much more than a normal planter would be. The sensors include a capacitive soil moisture sensor, a temperature sensor, and a light-dependent resistor. These sensors all provide analog outputs to relay their measurements and so there was an ADS1115 analog-to-digital converter board also included as the Raspberry Pi doesn’t have the required analog pins to communicate with them.

The fun animated faces are displayed with a 2-inch LCD display embedded in the planter. A small acrylic cover is placed in front of the LCD to help ease the transition from the printed planter to the internally mounted screen. The temperature and light sensors were also placed in openings around the planter to ensure they could get good environmental readings. There are six expressions the Fytó can express based on its sensor readings, ranging from happy when all the readings are in a good zone, to thirsty if it needs water or freezing when it’s too cold. Be sure to check out the other entries in the 2025 Pet Hacks Contest.

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Automated Blinds Opener On The Cheap

May 27, 2025 by Matt Varian 7 Comments

We love seeing hacks that involve salvaging parts from what you have on hand to make a new project work, and this project is a great example of that. [Simon], in a quick weekend build, created an automated blinds opener using parts he had available.

The project began with the desire to have his blinds open slowly and silently, gradually letting in more light. To accomplish this, a few key components were needed, including a motor with a gearbox to provide the torque required to actuate the blinds and a magnetic encoder to track their progress. To isolate vibrations and keep the system silent, the motor is mounted using a silicone motor mount that he salvaged from a broken water flosser.

The printed holder for the magnetic encoder is a nice touch.

To mount the motor to the wall near the window, he used some 3D printed parts. A clever combination of surgical silicone tubing and silicone tape attaches the motor to the window blind shaft while limiting vibration transfer, keeping things quiet. [Simon] advises against using magnetic encoders as he did, noting that while he had them on hand and made them work, the magnetic shaft’s misalignment with the encoders makes it a less-than-ideal approach. Nevertheless, he got it working.

Automating blinds is a fairly common project around these parts, made all the more accessible with clever 3D printed mechanisms. We’ve even seen variations that can be used in rentals, dorms, and other places were permanent modifications need to be avoided.