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?

Custom Fan Controller For Otherwise Fanless PCs

October 29, 2024 by Bryan Cockfield 6 Comments

Most of us using desktop computers, and plenty of us on laptops, have some sort of fan or pump installed in our computer to remove heat and keep our machines running at the most optimum temperature. That’s generally a good thing for performance, but comes with a noise pollution cost. It’s possible to build fanless computers, though, which are passively cooled by using larger heat sinks with greater thermal mass, or by building more efficient computers, or both. But sometimes even fanless designs can benefit from some forced air, so [Sasa] built this system for cooling fanless systems with fans.

The main advantage of a system like this is that the fans on an otherwise fanless system remain off when not absolutely necessary, keeping ambient noise levels to a minimum. [Sasa] does have a few computers with fans, and this system helps there as well. Each fan module is WiFi-enabled, allowing for control of each fan on the system to be set up and controlled from a web page. It also can control 5V and 12V fans automatically with no user input, and can run from any USB power source, so it’s not necessary to find a USB-PD-compatible source just to run a small fan.

Like his previous project, this version is built to easily integrate with scripting and other third-party software, making it fairly straightforward to configure in a home automation setup or with any other system that is monitoring a temperature. It doesn’t have to be limited to a computer, either; [Sasa] runs one inside a server cabinet that monitors the ambient temperature in the cabinet, but it could be put to use anywhere else a fan is needed. Perhaps even a hydroponic setup.

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How Hot Is That Soldering Iron?

September 7, 2024 by Al Williams 8 Comments

It is common these days to have a soldering iron where you can set the temperature using some sort of digital control. But how accurate is it? Probably pretty accurate, but [TheHWCave] picked up a vintage instrument on eBay that was made to read soldering iron temperature. You can see the video below, which includes an underwhelming teardown.

The device is a J thermocouple and a decidedly vintage analog meter. What’s inside? Nearly nothing. So why did the meter not read correctly? And where is the cold junction compensation?

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Upgrading PC Cooling With Software

March 9, 2024 by Bryan Cockfield 21 Comments

As computing power increases with each new iteration of processors, actual power consumption tends to increase as well. All that waste heat has to go somewhere, and while plenty of us are content to add fans and heat sinks for a passable air-cooled system there are others who prefer a liquid cooling solution of some sort. [Cal] uses a liquid cooler on his system, but when he upgraded his AMD chip to one with double the number of cores he noticed the cooling fans on the radiator were ramping quickly and often. To solve this problem he turned to Python instead of building a new cooling system.

The reason for the rapid and frequent fan cycling was that the only trigger for the cooling fans available on his particular motherboard is CPU temperature. For an air cooled system this might be fine, but a water cooled system with much more thermal mass should be better able to absorb these quick changes in CPU temperature without constantly adjusting fan speed. Using a python script set up to run as a systemd service, the control loop monitors not only the CPU temperature but also the case temperature and the temperature of the coolant, and then preferentially tries to dump heat from the CPU into the thermal mass of the water cooler before much ramping of cooling fans happens.

An additional improvement here is that the fans can run at a much lower speed, reducing dust in the computer case and also reducing noise compared to before the optimizations. The computer now reportedly runs almost silently unless it has been under load for several minutes. The script is specific to this setup but easily could be modified for other computers using liquid cooling, and using Grafana to monitor the changes can easily be done as [Cal] also demonstrates when calibrating and testing the system. On the other hand, if you prefer a more flashy cooling system as a living room centerpiece, we have you covered there as well.

Thermal Earring Tracks Body Temperature

February 13, 2024 by Kristina Panos 11 Comments

If you want to constantly measure body temperature to track things like ovulation, you usually have to wear something around your wrist or finger in the form of a smartwatch or ring. Well, what if you can’t or don’t want to adorn yourself this way? Then there’s the thermal earring.

Developed at the University of Washington, the thermal earring is quite small and unobtrusive compared to a smartwatch. Sure, it dangles, but that’s so it can measure ambient temperature for comparison’s sake.

You don’t even need to have pierced ears — the earring attaches to the lobe magnetically. And yeah, the earring can be decorated to hide the circuitry, but you know we would rock the bare boards.

The earring uses BLE to transmit readings throughout the day, and of course goes into sleep mode between transmissions to save power. Coincidentally, it runs for 28 days per charge, which is the length of the average menstrual cycle. While the earring at this time merely “shows promise” as a means of monitoring stress and ovulation, it did outperform a smartwatch at measuring skin temperature while the wearers were at rest.

This is definitely not the only pair of earrings we’ve got around here. These art deco earrings use flexible PCBs, and this pair will light up the night.

A General-Purpose PID Controller

January 27, 2024 by Bryan Cockfield 19 Comments

For those new to fields like robotics or aerospace, it can seem at first glance that a problem like moving a robot arm or flying an RC airplane might be simple problems to solve. It turns out, however, that control of systems like these can get complicated quickly; so much so that these types of problems have spawned their own dedicated branch of engineering. As controls engineers delve into this field, one of their initial encounters with a control system is often with the PID controller, and this open source project delivers two of these general-purpose controllers in one box.

The dual-channel PID controller was originally meant as a humidity and temperature controller and was based on existing software for an ATmega328. But after years of tinkering, adding new features, and moving the controller to an ESP32 platform, [knifter] has essentially a brand new piece of software for this controller. Configuring the controller itself is done before the software is compiled, and it includes a GUI since one of the design goals of the project was ease-of-use. He’s used it to control humidity, temperature and CO2 levels in his own work at the University of Amsterdam, but imagines that it could see further use outside of his use cases in things like reflow ovens which need simple on/off control or for motors which can be controlled through an H-bridge.

The PID controller itself seems fairly robust, and includes a number of features that seasoned controls engineers would look for in their PID controllers. There are additionally some other open-source PID controllers to take a look at like this one built for an Arduino, and if you’re still looking for interesting use cases for these types of controllers one of our favorites is this PID controller built into a charcoal grill.

Temperature Measurement By Wire

December 27, 2023 by Al Williams 7 Comments

There’s an old joke about how to tell how tall a building is using a barometer. The funniest answer is to find the building owner and offer them a nice barometer in exchange for the information. We wonder if [DiodeGoneWild] has heard that one since his recent video details how to measure temperatures using an ohmmeter.

The idea is that wire changes its resistance based on temperature. So if you know the resistance of a lot of wire — maybe a coil — at room temperature and you can measure the resistance at temperature, it is entirely feasible to calculate the amount of temperature that would cause this rise in resistance.

Of course, there are many ways to measure resistance, too. It’s probably possible to measure parameters like operating current and estimate temperature for at least some circuits. The wire’s material also plays a part, and the online calculator lets you choose copper, aluminum, iron, or tungsten. You also need a lot of wire, a very accurate resistance measurement, or, preferably, both.

There are many ways to accurately measure resistance, of course. Then again, you can also get resistors specifically for the job.

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