ATTiny NFC Thermometer keychain with keys

Tiny NFC-Powered Keychain Thermometer

December 8, 2024 by Heidi Ulrich 9 Comments

What if your keychain could tell you the temperature, all while staying battery-free? That’s the essence of this innovative keychain ‘NFC_temp’ by [bjorn]. This nifty gadget harnesses energy from an NFC field—like the one created by your smartphone—to power itself just long enough to take a precise temperature reading. Using components like an ATTiny1626 microcontroller, a TMP117 thermometer, and an RF430CL330H NFC IC, NFC_temp cleverly stores harvested power in a capacitor to function autonomously.

The most impressive part? This palm-sized device (18×40 mm) uses a self-designed 13.56 MHz antenna to draw energy from NFC readers. The temperature is then displayed on the reader, with an impressive accuracy of ±0.1 °C. Creator [bjorn] even shared challenges, like switching from an analog sensor due to voltage instability, which ultimately led to his choice of the TMP117. Android phones work best with the tag, while iOS devices require a bit more angling for reliable detection.

Projects like NFC_temp underscore the creativity within open source. It’s a brilliant nod to the future of passive, wireless, energy-efficient designs. Since many of us will all be spending a lot of time around the Christmas tree this month, why not fit it in a bauble?

Building An IR Thermometer That Fits On Your Keychain

July 5, 2024 by Tom Nardi 11 Comments

Non-contact infrared (IR) thermometers used to be something of an exotic tool, but thanks at least in part due to the COVID-19 pandemic, they’re now the sort of thing you see hanging up near the grocery store checkout as a cheap impulse buy. Demand pushed up production, and the economies of scale did the test. Now the devices, and the sensors within them, are cheap enough for us hackers to play with.

The end result is that we now have projects like this ultra compact IR thermometer from [gokux]. With just a handful of components, some code to glue it all together, and a 3D printed enclosure to wrap it all up, you’ve got a legitimately useful tool that’s small enough to replace that lucky rabbit’s foot you’ve got on your keys.

If this project looks familiar, it’s because the whole thing is closely related to the LiDAR rangefinder [gokux] put together last month. It shares the same Seeed Studio XIAO ESP32-C3 microcontroller, 0.49 inch OLED display, and tiny 40 mAh LiPo battery. The only thing that’s really changed, aside from the adjustments necessary to the 3D printed enclosure, is that the LiDAR sensor was replaced with a MLX90614 IR temperature sensor.

[gokux] has put together some great documentation for this build, making it easy for others to recreate and remix on their own. Assembly is particularly straightforward thanks to the fact that both the display and temperature sensor communicate with the ESP32 over I2C, allowing them to be wired daisy chain style — there’s no need for even a scrap of perfboard inside the case, let alone a custom board.

What Is This, A Controller For Ants?!

January 31, 2018 by James Hobson 6 Comments

What’s the smallest controller you’ve ever used? [BitBuilt] forum user [Madmorda] picked up a cool little GameCube controller keychain with semi-working buttons at her local GameStop. As makers are wont to do, she figured she could turn it into a working controller and — well — the rest is history.

This miniaturized controller’s original buttons were essentially one piece of plastic and all the buttons would depress at once — same goes for the D-pad. Likewise, the original joystick and C-stick lacked springs and wouldn’t return to a neutral position after fidgeting with them. To get the ball rolling, [Madmorda] picked up a GC+ board — a custom GameCube controller board — just small enough to fit this project, eleven hard tact switches for the various buttons, and two squishy tact switches to replicate the original controller’s L and R button semi-analog, semi-digital functionality.

Continue reading “What Is This, A Controller For Ants?!” →

Surprise Your Loved One With A Heart Keychain

November 15, 2017 by Will Sweatman 20 Comments

Sometimes the simplest projects can be the most impressive. Most of the time our simple projects are not as neat and elegant as our more time consuming ones. Sometimes they don’t even leave the breadboard! When [Sasa Karanovic] first envisioned his key-chain idea, he knew it would be simple. But he made up for the lack of sophistication with style.

The heart-shaped key-chain has one goal – to flash a pair of red LEDs when a capacitive button is touched. He was able to accomplish this with a PIC12LF1822 and a handful of supporting components. We’re quite impressed with the soldering skills and layout of the PCB. The resistors, LEDs and single capacitor are 0603 surface mount devices, which push the limits of hand soldering. [Sasa] gives a great explanation of how capacitive touch buttons work and how they can be easily incorporated directly into a PCB.

What’s the smallest SMD you’ve soldered? Let us know in the comments, along with what you think about this nifty key-chain.

Quick Robin! The Bat Keychain!

August 9, 2017 by Al Williams 3 Comments

We don’t know if Batman has a keychain for the keys to the Bat mobile, the Bat copter, and all his other vehicles. But we are guessing if he did, it didn’t look like the one [krishnan793] picked up cheap. It had a little button that lit up some LEDs and played a little tune. [Krishnan] thought he could do better with an ESP8266. After chopping up some headphones and adding a LiPo battery, he wound up with an improved key chain you can see in the video below. The first video is the before video. The second is after the modification. Sure, it is only a small improvement on LEDs and a simple tune, but now it is hackable to do more interesting things if you want to take the trouble to do so.

Continue reading “Quick Robin! The Bat Keychain!” →

Multipurpose ESP8266 Keychain

May 21, 2017 by Inderpreet Singh 30 Comments

One of the best feature of the ESP8266 is its ability to self-host a web server, allowing for fairly complicated user interactions. The dEEbugger by [S-March] is a nifty little ESP8266 based device with a plethora of features in a small package.

The USB-powered device has a web user interface that enables it to be used as a low-bandwidth oscilloscope, I2C terminal, or UART terminal. As a scope, you may connect to it via your tablet and then use it as a remote voltage monitor. There is a peak detection feature which is a nice touch and gives the entire project a premium feel.

The serial terminal on an ESP8266 is not something new yet it is helpful in disconnecting the console window from the bench. The I2C terminal is where the device really shines as it can scan for connected devices on the connected bus. This Bus-Pirate like feature is useful for beginners as the software can scan the registers addresses of the devices as well.

[S-March] has made the schematic in PDF format as well as the entire code for the project available on GitHub so go right ahead and make it your own. We have had an ESP8266 based VT Terminal device in the past and merging the two would make for an excellent maker tool.

Thanks for the tip [René Arts]

Blu-Ray Laser Keychain

June 25, 2009 by Zach Banks 56 Comments

blu-ray-laser

[Jay] hacked a Blu-Ray laser diode into a keychain enclosure. He found a heavy brass keychain light from Lowe’s and stuffed the diode and a larger battery inside. The existing batteries weren’t powerful enough, so he drilled out the endcap to fit a 200mAh 3.6v lithium battery inside. He also modded the power button to only momentarily turn on the diode. With the larger battery, the laser can run for about an hour between charges. In addition to a Blu-Ray lasers, he also has versions with a 200mW red diode.

Related: Laser projector zippo