Hackaday Prize Entry: MappyDot, a Micro Smart LiDAR Sensor

[Blecky]’s entry to the Hackaday Prize is MappyDot, a tiny board less than a square inch in size that holds a VL53L0X time-of-flight distance sensor and can measure distances of up to 2 meters.

MappyDot is more than just a breakout board; the ATMega328PB microcontroller on each PCB provides filtering, an easy to use  I2C interface, and automatically handles up to 112 boards connected in a bus. The idea is that one or a few MappyDots can be used by themselves, but managing a large number is just as easy. By dotting a device with multiple MappyDots pointing in different directions, a device could combine the readings to gain a LiDAR-like understanding of its physical environment. Its big numbers of MappyDots [Blecky] is going for, too: he just received a few panels of bare PCBs that he’ll soon be laboriously populating. The good news is, there aren’t that many components on each board.

It’s great to see open sourced projects and tools in which it is clear some thought has gone into making them flexible and easy to use. This means they are easier to incorporate into other work and helps make them a great contestant for the Hackaday Prize.

GPS Tracker Gets SMS Upgrade

In May of 2000, then-President Bill Clinton signed a directive that would improve the accuracy of GPS for anyone. Before this switch was flipped, this ability was only available to the military. What followed was an onslaught of GPS devices most noticeable in everyday navigation systems. The large amount of new devices on the market also drove the price down to the point where almost anyone can build their own GPS tracking device from scratch.

The GPS tracker that [Vadim] created makes use not just of GPS, but of the GSM network as well. He uses a Neoway M590 GSM module for access to the cellular network and a NEO-6 GPS module. The cell network is used to send SMS messages that detail the location of the unit itself. Everything is controlled with an ATmega328P, and a lithium-ion battery and some capacitors round out the fully integrated build.

[Vadim] goes into great detail about how all of the modules operate, and has step-by-step instructions on their use that go beyond what one would typically find in a mundane datasheet. The pairing of the GSM and GPS modules seems to go match up well together, much like we have seen GPS and APRS pair for a similar purpose: tracking weather balloons.

8-bit Computer for On-The-Go Programming

If there was one downside to 8-bit computers like the Commodore 64, it’s that they weren’t exactly portable. Even ignoring their physical size, the power requirements would likely have required a prohibitively large power bank of some sort to lug around as well. The problem of portability has been solved since the late ’70s, but if you still want that 8-bit goodness in a more modern package you’ll have to look at something like retrocomputing madman [Jack Eisenmann]’s DUO Travel computer.

The computer is based around the ubiquitous ATmega328 which should make the ease at which it is programmable apparent. Even so, its 14-button keypad makes it programmable even without another computer. While it has slightly less memory than a standard C-64, it’s still enough for most tasks. And, since its powered by a 9-volt battery it doesn’t require any external power sources either.

The most impressive part of the build, however, is the custom programming language specifically tailored for this platform. After all, a 14-button keypad wouldn’t be a great choice if you had to program in Perl or C all the time. There is some example code on the project page for anyone interested in this specific implementation. While it’s not the most minimal computer [Jack] has ever built, it’s certain to be much more practical.

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Energy Harvesting Wristwatch Uses a Versatile Photodiode

There’s some interesting technology bundled into this energy harvesting wristwatch. While energy harvesting timepieces (called automatic watches) have been around for nearly 240 years, [bobricius] has used parts and methods that are more easily transferable to other projects.

Unlike early mechanical systems, this design uses the versatile BPW34 PIN photodiode (PDF warning). PIN photodiodes differ from ordinary PN diodes in that there’s a layer of undoped ‘intrinsic’ silicon separating the P and N doped layers. This reduces the utility of the diode as a rectifier, while allowing for higher quantum efficiency and switching speed.

They are typically used in the telecommunications industry, but have a number of interesting ‘off label’ applications. For example, the BPW34 can be used as a solid-state particle detector (although for detecting alpha particles you’re better off with something in a TO-5 package such as the Hamamatsu S1223-01). The fast response speed means you can send data with lasers or ambient light at high frequencies – a fun use for an LED lighting system or scrap DVD-RW laser.

Some common solar panels are essentially large PIN photodiodes. These are the brownish panels that you’ll find in a solar-powered calculator, or one of those eternally waving golden plastic neko shrines. They specifically offer excellent low-light performance, which is the basis of the energy harvesting used in this project.

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Precision Pressure In A Piston

[Scott] is building a DIY yeast reactor for his aquarium. What’s a yeast reactor? [Scott] wants to pump carbon dioxide into his aquarium so his aquatic plants grow more. He’s doing this with a gallon of sugary, yeasty water bubbling into a tank of plants and fish. In other words, [Scott] is doing this whole thing completely backward and utilizing the wrong waste product of the yeast metabolism.

However, along the way to pumping carbon dioxide into his aquarium, [Scott] created a very high precision pressure sensor. It’s based on a breakout board featuring the MS5611 air pressure sensor. This has a 24-bit ADC on board, which translates into one ten-thousandths of a pound per square inch of pressure.

To integrate this pressure sensor into the aquarium/unbrewery setup, [Scott] created a pressure meter out of a syringe. With the plunger end of this syringe encased in epoxy and the pointy end still able to accept needles, [Scott] is able to easily plug this sensor into his yeast reactor. The data from the sensor is accessible over I2C, and a simple circuit with an ATmega328 and a character LCD displays the current pressure in the syringe.

We’ve seen these high-resolution pressure sensors used in drones and rockets as altimeters before, but never as a pressure gauge. This, though, is a cheap and novel solution for measuring pressures between a vacuum and a bit over one atmosphere.

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Thermal Panorama One Pixel At A Time

Inspiration can strike from the strangest places. Unearthing a forgotten Melexis MLX90614 thermopile from his  ‘inbox,’ [Saulius Lukse] used it to build a panoramic thermal camera.

[Lukse] made use of an ATmega328 to control the thermal sensor, and used the project to test a pair of two rotary stage motors he designed for tilt and pan, with some slip rings to keep it in motion as it captures a scene. That said, taking a 720 x 360 panoramic image one pixel at a time takes over an hour, and compiling all that information into an intelligible picture is no small feat either. An occasional hiccup are dead pixels in the image, but those are quickly filled in by averaging the temperature of adjoining pixels.

The camera  rig works — and it does turn out a nice picture — but [Lukse]  says an upgraded infrared camera to captured larger images at a time and higher resolution would not be unwelcome.


Another clever use of a thermopile might take you the route of this thermal flashlight. if you don’t build your own thermal camera outright.

[Thanks for the tip, Imn!]

T-Rex Runner Runs on Transistor Tester

If you’ve ever spent time online buying electronic doodads — which would mean almost all of us — then sooner or later, the websites get wind of your buying sprees and start offering “suggested” advertisements for buying more useless stuff. One commonly offered popular product seems to be a universal component tester, often referred to as a “Mega328 Transistor Tester Diode Triode Capacitance ESR Meter”. These consist of an ATmega328, an SPI LCD display, a Button, a ZIF socket and a few other components. Almost all of them are cheap clones of the splendid AVR-TransistorTester project by [Markus Frejek]. [Robson Couto] got one of these clone component testers, and after playing with it for a while, decided to hack it and write a T-Rex runner game for it.

The T-Rex runner game is Chrome’s offering for you to while away your time when it can’t connect to the internet. It needs just one button to play. This is just the kind of simple game that can be easily ported to the Component Tester. The nice take away from [Robson]’s blog post is not that he wrote a simple game for an ATmega connected to an LCD display, but the detailed walk through he provides of the process which can be useful to anyone else wanting to dip their feet in the world of writing games.

After a bit of online sleuthing and some multimeter testing, he was able to figure out that the LCD controller chip was connected to Port D of the ATmega, which meant the use of software SPI via bit-banging. He then looked inside the disassembled firmware to find writes to Port D to figure out pin assignments. Of course not long after all this work he found a config.h file with the pin mappings.

Armed with this information he was able to use the Adafruit ST7565 library to drive the LCD, but not before having to flip the image. The modified fork of his ST7565 library is available on GitHub. His game code is also available, but reading through the development process is pretty interesting. Check out a video of the Runner game in action after the break.

In an earlier post, we did a product review of one of these cheap Transistor Testers, and if you have one of these lying around, give [Robson]’s game a spin — it could be handy while you wait for your reflow oven to finish its soldering cycle.

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