Gesture Sensing With A Temperature Sensor

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.

BSD Breathes New Life Into Obsolete Equipment

An old laptop or desktop computer that’s seen better days might still have a little bit of use left in it for a dedicated task. Grabbing a lightweight flavor of Linux and running a web server, firewall, or Super Nintendo emulator might get a few more years out of it. You can also get pretty creative repurposing obsolete single purpose  machines, as [Kristjan] did with some old Cisco server equipment.

The computer in question isn’t something commonly found, either. It’s an intrusion detection system meant to mount in a server rack and protect the server itself from malicious activity. While [Kristjan] mentions that Cisco equipment seems to be the definition of planned obsolescence, we think that this Intel Celeron machine with an IDE hard drive may have gone around the bend quite some time ago. Regardless, it’s modern enough to put back to work in some other capacity.

To that end, a general purpose operating system was installed, and rather than use Linux he reached for BSD to get the system up and running. There’s one other catch, though, besides some cooling issues. Since the machine was meant to be used in a server, there’s no ACPI which means no software shutdown capability. Despite all the quirks, you can still use it to re-implement a network security system if you wanted to bring it full-circle.

A Foggy Lightsaber Build

Lightsabers have enchanted audiences since their appearance in the very first Star Wars film in 1977. Unfortunately, George Lucas hasn’t shared the technology in the years since then with the broader public, so we’re left to subsist on pale imitations. This is just such a build.

The closest human analog to Jedi technology is the laser, and this build uses 8 of them in combination with two LEDs. They’re aimed to coincide at a fixed distance above the hilt. A CO2 bicycle inflater is then used to blow through an e-cigarette to create a fog. This makes the red lasers readily visible to the human eye.

This ersatz lightsaber does have its limitations – fast motion tends to scatter the fog, making it once again invisible, and it’s really at its best held in a vertical orientation. There’s also some divergence beyond the focused point. With that said, it does look somewhat impressive when held still, smouldering away.

Until we gain a better mastery of plasma physics, perhaps you can make do with this fire-based build? Video after the break.

[Thanks to qrp-gaijin for the tip!]

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Underclocking the ESP8266 Leads To WiFi Weirdness

Sometimes the best hacks come from the most basic of questions. In this case, [CNLohr] was wondering what would happen if he started to reduce the clock speed of the ESP8266’s Baseband PLL (BBPLL) while still trying to communicate with it. You know, as one does. The results ended up being fairly surprising, and while it’s not immediately clear if there’s a practical application for this particular trick, it’s certainly worth some additional research.

Code for stepping through clock speeds

The idea here is that the BBPLL is the reference clock for the entire system, including all of the peripherals. So underclocking it doesn’t just slow down code execution as you might expect, but it also slows down the chip’s interactions with the outside world. [CNLohr] demonstrates this concept in the video below, showing how the baud rate used to view the serial output from the ESP8266 needs to be adjusted to match the chip’s frequency or else you’ll only get garbage on the line.

But what happens to the WiFi? As [CNLohr] discovered, while the center frequency itself doesn’t change, the channel width gets narrower as the clock rate is lowered. When viewed on the waterfall display of a software defined radio (SDR), the transmission can be seen “compressing” in a step pattern as the clock rate is reduced. As one might expect, the 802.11 packets become indecipherable to a normal WiFi device running in monitor mode. The signal is still at the correct frequency, but the devices can no longer understand each other.

Now it was time for another of those basic questions. What would happen if you did the same thing to a second ESP8266? Much to his surprise, [CNLohr] discovered that the two devices could still communicate successfully as long as their BBPLL clock speed was the same. From an outsider’s perspective it looked like gibberish, but to the two ESPs which had been slowed by the same amount, everything worked as expected even though the 802.11 standards say it shouldn’t.

So what can you do with this? The most obvious application is a “stealth” WiFi connection between ESP8266s which wouldn’t show up to normal devices, a communications channel invisible to all but the most astute eavesdropper. [CNLohr] has made all the source code to pull this trick off public on GitHub, and it should be interesting to see what kind of applications (if any) hackers find for this standards-breaking behavior.

If your thing is devices being forced into operations they were never intended to by particularly twisted hackers, check out our recent coverage of the USB serial adapter turned SDR by [Ted Yapo].

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Return of the Logic Probe

We live in a day when it is very inexpensive to buy an oscilloscope, especially one with modest performance that hooks to a laptop. However, there was a time when even a surplus scope was out of reach for many people who liked to build things. A common alternative was the logic probe. At the low end, this could be an inverter and an LED, although it was more common to have a little extra circuitry to actually do a comparison to a reference voltage and present some indication of fast pulses — you might not be able to tell the frequency of a clock, but you could tell it wasn’t stuck. Of course, today with a microcontroller you can make a very sophisticated probe with less circuitry than a classic probe. We’ve seen a few takes on this and the latest is the DigiLogicProbe from [TheRadMan].

The probe is just a ATtiny85 board with a handful of components. A resistor and diode help protect the probe and the circuit under test. There are also a few LEDs and a buzzer. The rest of the project is software.

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Finding the Goldilocks Cell Module

If adding a cell modem is dealing with a drama queen of a hardware component, then choosing from among the many types of modules available turns the designer into an electronics Goldilocks. There are endless options for packaging and features all designed to make your life easier (or not!) so you-the-designer needs to have a clear understanding of the forces at work to come to a reasonable decision. How else will Widget D’lux® finally ship? You are still working on Widget D’lux®, aren’t you?

OK, quick recap from last time. Cell modems can be used to add that great feature known as The Internet to your product, which is a necessary part of the Internet of Things, and thus Good. So you’re adding a cell modem! But “adding a cell modem” can mean almost anything. Are you aiming to be Qualcomm and sue Apple build modems from scratch? Probably not. What about sticking a Particle Electron inside to bolt something together quickly? Or talk to Telit and put a bare modem on a board? Unless you’re expecting to need extremely high volume and have a healthy appetite for certification glee, I bet you’ve chosen to get a modem with as many existing certifications as possible, which takes us to where we are today. Go read the previous post if you want a much more elaborate discussion of your modem-packaging options and some of the trade offs involved. Continue reading “Finding the Goldilocks Cell Module”

The Mystery of the Clacking Clanking Scraping Sound

Hackers tend to face household problems a little differently than ordinary folk. Where the average person sees a painful repair bill or a replacement appliance, the hacker sees a difficult troubleshooting job and the opportunity to save some cash. [trochilidae] was woken one day by the dreaded Clacking Clanking Scraping Sound, or CCSS, and knew that something had to be done.

[trochilidae] reports that usually, the CCSS is due to the child of the house destroying his lodgings, but in this case, the source was laundry based. The Miele tumble dryer was acting up, and in need of some attention. What follows is a troubleshooting process [AvE] would be proud of – careful disassembly to investigate the source of the problem. Initial efforts found a loose bulb that was unrelated, before landing on a mysterious spring that wouldn’t fit back into place. In the end, that’s because it had no right to be there at all – an underwire had escaped from a bra, before becoming entangled in the dryer’s bearing. With the culprit identified and removed, it was a simple reassembly job with some attention also paid to the condenser and filters to keep things in ship-shape.

It just goes to show – a bad noise, if properly investigated in a prompt manner, doesn’t have to be the end of the world. A bit of investigation goes a long way, and can save you a lot of money and heartache.

We’ve seen appliances giving hackers trouble before – like this aging washing machine that got its mechanical brain replaced with an Arduino.