Good science fiction has sound scientific fact behind it and when Tony Stark first made his debut on the big screen with design tools that worked at the wave of a hand, makers and hackers were not far behind with DIY solutions. Over the years the ideas have become much more polished, as we can see with this Gesture Recognition with PIR sensors project.
The project uses the TPA81 8-pixel thermopile array which detects the change in heat levels from 8 adjacent points. An Arduino reads these temperature points over I2C and then a simple thresholding function is used to detect the movement of the fingers. These movements are then used to do a number of things including turn the volume up or down as shown in the image alongside.
The brilliant part is that the TPA81 8-Pixel sensor has been around for a number of years. It is a bit expensive though it has the ability to detect small thermal variations such as candle flames at up to 2 Meters. More recent parts such as the Panasonic AMG8834 that contain a grid of 8×8 such sensors are much more capable for your hacking/making pleasure, but come with an increased price tag.
This technique is not just limited to gestures, and can be used in Heat-Seeking Robots that can very well be trained to follow the cat around just to annoy it.
When they need to add temperature control to a project, many hackers reach for a K-type thermocouple for their high-temperature needs, or an integrated temperature-sensing IC when it doesn’t get that hot. The thermocouple relies on very small currents and extremely high gain, and you pretty much need a dedicated IC to read it, which can be expensive. The ICs aren’t as expensive, but they’re basically limited to boiling water. What do you do if you want to control a reflow oven?
There’s a cheaper way that spans a range between Antarctic winter and molten solder, and you’ve probably already got the parts on your shelf. Even if you don’t, it’s only going to run you an extra two cents, assuming that you’ve already got a microcontroller with an ADC in your project. The BOM: a plain-vanilla diode and a resistor.
I’ve been using diodes as temperature sensors in three projects over the last year: one is a coffee roaster that brings the beans up to 220 °C in hot air, another is a reflow hotplate that tops out around 210 °C, and the third is a toner-transfer iron that holds a very stable 130 °C. In all of these cases, I don’t really care about the actual numerical value of the temperature — all that matters is reproducibility — so I never bothered to calibrate anything. I thought I’d do it right for Hackaday, and try to push the humble diode to its limits for science.
What resulted was a PCB fire, test circuits desoldering themselves above 190 °C, temperature probes coming loose, and finally a broken ramekin and 200 °C peanut oil all over my desk. Fun times! On the other hand, I managed to get out enough data to calibrate some diodes, and the results are fantastic. The circuits under test included both best practices and the easiest thing that could possibly work, and the results are pretty close. This is definitely a technique that you want to have under your belt for most temperature ranges. The devil is in the details, of course, so read on!
Stick a 10kΩ pot in the left-side header and you can play a space shooter game, or make line drawings by twisting the knob like an Etch-A-Sketch. Be sure to check out the detailed walk-through after the break, and a bonus video that shows off Multiduino’s newest functions including temperature sensing, a monophonic music player for sweet chiptunes, and a virtual keyboard for scrolling text on the OLED screen. [Danko] has a few of these for sale in his eBay store. They come assembled, and he ships worldwide. The code for every existing function is available on his site.
We love to highlight great engineering student projects at Hackaday. We also love environment-sensing microcontrollers, 3D printing, and jet engines. The X-Plorer 1 by JetX Engineering checks all the boxes.
This engineering student exercise took its members through the development process of a jet engine. Starting from a set of requirements to meet, they designed their engine and analyzed it in software before embarking on physical model assembly. An engine monitoring system was developed in parallel and integrated into the model. These embedded sensors gave performance feedback, and armed with data the team iterated though ideas to improve their design. It’s a shame the X-Plorer 1 model had to stop short of actual combustion. The realities of 3D printed plastic meant airflow for the model came from external compressed air and not from burning fuel.
Also worth noting are the people behind this project. JetX Engineering describe themselves as an University of Glasgow student club for jet engine enthusiasts, but they act less like a casual gathering of friends and more like an aerospace engineering firm. The ability of this group to organize and execute on this project, including finding sponsors to fund it, are skills difficult to teach in a classroom and even more difficult to test with an exam.
After X-Plorer 1, the group has launched two new project teams X-Plorer 2 and Kronos. They are also working to expand to other universities with the ambition of launching competitions between student teams. That would be exciting and we wish them success.
Brewing beer or making wine at home isn’t complicated but it does require an attention to detail and a willingness to measure and sanitize things multiple times, particularly when tracking the progress of fermentation. This job has gotten easier thanks to the iSpindel project; an ESP8266 based IoT device intended as a DIY alternative to a costly commercial solution.
Tracking fermentation normally involves a simple yet critical piece of equipment called a hydrometer (shown left), which measures the specific gravity or relative density of a liquid. A hydrometer is used by winemakers and brewers to determine how much sugar remains in a solution, therefore indicating the progress of the fermentation process. Using a hydrometer involves first sanitizing all equipment. Then a sample is taken from the fermenting liquid, put into a tall receptacle, the hydrometer inserted and the result recorded. Then the sample is returned and everything is cleaned. [Editor (and brewer)’s note: The sample is not returned. It’s got all manner of bacteria on/in it. Throw those 20 ml away!] This process is repeated multiple times, sometimes daily. Every time the batch is opened also increases the risk of contamination. Continue reading “IoT Device Pulls Its Weight in Home Brewing”→
The folks at Swindon Makerspace took possession of a new space a few months ago after a long time in temporary accommodation. They’ve made impressive progress making it their own, and are the envy of their neighbours.
A small part of the new space is a temperature logger, and it’s one whose construction they’ve detailed on their website. It’s a simple piece of hardware based around a Dallas DS18B20 1-wire temperature sensor and an ESP8266 module, powered by 3 AA batteries and passing its data to data.sparkfun.com. The PCB was created using the space’s CNC router, and the surface-mount components were hand-soldered. The whole thing is dwarfed by its battery box, and will eventually be housed in its own 3D printed case. Sadly they’ve not posted the files, though it’s a simple enough circuit that’s widely used, it looks similar to this one with the addition of a voltage regulator.
The device itself isn’t really the point here though, instead it serves here to highlight the role of a typical small hackspace in bringing simple custom electronic and other prototyping services to the grass roots of our community. Large city hackspaces with hundreds of members will have had the resources to create the space program of a small country for years, but makers in provincial towns like Swindon – even with their strong engineering heritage – have faced an uphill struggle to accumulate the members and resources to get under way.
So to the wider world it’s a simple temperature logger but it really represents more than that — another town now has a thriving and sustainable makerspace. Could your town do the same?
Most of North America has been locked in a record-setting heat wave for the last two weeks, and cheap window AC units are flying out of the local big-box stores. Not all of these discount units undergo rigorous QC before sailing across the Pacific, though, and a few wonky thermostats are sure to get through. But with a little sweat-equity you can fix it with this Arduino thermostat and temperature display.
We’ll stipulate that an Arduino may be overkill for this application and that microcontrollers don’t belong in every project. But if it’s what you’ve got on hand, and you’re sick of waking up in a pool of sweat, then it’s a perfectly acceptable solution. It looks like [Engineering Nonsense] got lucky and had a unit with a low-current power switch, allowing him to use a small relay to control the AC. The control algorithm is simple enough – accept a setpoint from an encoder, read the temperature sensor, and turn the AC on or off accordingly. Setpoint and current temperature are displayed on an OLED screen. One improvement we’d suggest is adding a three-minute delay between power cycles like the faceplate of the AC states.
This project bears some resemblance to this Arduino-controlled AC, but it seems more hackish to us. And that’s a good thing – hackers have to keep cool somehow.