A Peek Into A Weed-Eating Robot’s Test Fixtures

July 7, 2018 by Donald Papp 2 Comments

When it comes to production, fast is good! But right the first time is better. Anything that helps prevent rework down the line is worth investing in. Some of the best tools to catch problems are good test fixtures. The folks at Tertill (a solar-powered robot for killing weeds that kickstarted last year) took the time to share two brief videos of DIY test fixtures they use to test components before assembly.

The videos are short, but they demonstrate all the things that make a good test: on the motor tester there are no connectors or wires to fiddle with, the test starts automatically, and there is clear feedback via prominent LEDs. The UI board tester also starts automatically and has unambiguous LED feedback, and sports a custom board holder with a recess just the right shape for the PCB. Once the board is in, the sled is pushed like a drawer to make contact with the test hardware and begin the test. The perfectly formed recesses in both units serve another function as well; they act as a go/no-go test for the physical shape of the components and contacts being tested.

Both videos are embedded below; and while there isn’t much detail on the actual test hardware, we do spy a Raspberry Pi and at least two Adafruit logos among other hacker-familiar elements like laser-cut acrylic, 3D printed plastic, pogo pins, and a PVC junction box.

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This Smart Pill Uses A Stomach Acid Battery

July 7, 2018 by Steven Dufresne 34 Comments

[Curt White] is working on a smart pill whose copper-zinc battery will use his own stomach acid as the electrolyte. It’s not that unusual of an idea, MIT tested a similar approach in a pig. It’s also better than using lithium ion batteries, something we covered in this PSA.

His starting point is a small, hacked activity tracker with its Nordic nRF51822 ARM Cortex-M0 and Bluetooth LE SoC. Most everything else is removed. The battery electrodes are sewn onto a plastic mesh cut to the activity tracker’s dimensions. Three coin type super capacitors and a boost converter sit between the battery and the SoC.

He uses the Bluetooth LE for communication, sort of. BLE devices constantly transmit information about themselves and it’s this which you see when scanning for available devices. Included in that transmission is a UUID (Universally Unique Identifier) and a name (e.g. “smartpillxyz”). He has the pill transmit data by putting it in that name. This saves power by minimizing the time which the pill’s Bluetooth radio is turned on. The smartphone app extracts the data from these transmissions without ever connecting.

His goal is to monitor the voltage and the maximum current. This will tell him if his stomach acid battery works and what can be powered by it. First tests will use regurgitated gastric fluid and then later he’ll swallow the pill himself. As he puts it, why not, “people swallow and pass all kinds of weird stuff without a problem.” Thay may sound cavalier but judging by his hackaday.io page, he’s doing his homework.

Pinball Wizard Hacks Table For Tommy Stage Show

July 7, 2018 by Richard Baguley 9 Comments

Ever since he was a young hacker
[Mark Gibson] has messed with the silver ball.
From Soho down to Denver
he must have fixed them all.
But we ain’t seen anything like this
in any amusement hall.
That darn devious hacker
sure hacks a mean pinball.

He hacks it like an expert,
Becomes part of the machine
Automating all the bumpers
Always wiring clean
His table plays by automation,
And radio control for all
That darn devious hacker
sure hacks a mean pinball.

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A Unique Microphone Preamp

July 7, 2018 by Tom Nardi 5 Comments

We live in a world in which nearly any kind of gadget or tool you can imagine is just a few clicks away. In many respects, this has helped fuel the maker culture over the last decade or so; now that people aren’t limited to the hardware that’s available locally, they’re able to create bigger and better things than ever before. But it can also have a detrimental effect. One has to question, for instance, why they should go through the trouble of building something themselves when they could buy it, often for less than the cost of the individual components.

The critic could argue that many of the projects that grace the pages of Hackaday could be supplanted with commercially available counterparts. We don’t deny it. But the difference between buying a turn-key product and building an alternative yourself is that you can make it exactly how you want it. That is precisely why [Sam Izdat] created this truly one of a kind microphone preamplifier. Could he have bought one online for cheaper? Probably. Could he have saved himself an immense amount of time and effort? Undoubtedly. Do we care? Not in the slightest.

The amplifier is based on the Texas Instruments INA217 chip, with an Arduino Nano and 128×64 OLED display providing the visualization. [Sam] was able to find a bare PCB for a typical INA217 implementation on eBay for a few bucks (see what we mean?), which helped get him started and allowed him to spend more time on the software side of things. His visualization code offers a number of interesting display modes, uses Fast Hartley Transforms, and very nearly maxes out the Arduino.

But perhaps no element of this build is as unique as the case. The rationale behind the design is that [Sam] wanted to compartmentalize each section of the device (power supply, amplifier, visualization) to avoid any interference. The cylindrical shapes were an issue of practicality: the compartments were constructed by using a hole saw to make wooden discs, which were then glued together and hollowed out. The case was stained and coated with polyurethane, but due to some slightly overzealous use of glue and fillers, the coloring isn’t uniform. This gives the final piece a somewhat weathered look, in sharp contrast to the decidedly high-tech looking display.

Overall, this build reminds us of the modular 3D printed amplifier we saw earlier in the year combined with these speaker-integrated Arduino VU meters.

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There’s A Computer In This Hard Drive

July 7, 2018 by Brian Benchoff 21 Comments

Throughout the history of personal computers, there are some unique form factors. The 3com Audrey was sold as a computing appliance, meant to sit on a kitchen counter, to display recipes or something. For some reason, Macs were cubes once, and it actually wasn’t a bad machine. At one point, you were supposed to put a monitor on top of your computer.

A few years ago, [glitch] read about an interesting system from the early 80s. The SIIG S286 was designed by the same people that made SCSI cards and external hard drives, and it shows: this is a complete 286-based system stuffed into what was probably an external enclosure for a 5 1/4 drive at some point. After finding one of these bad boys on an auction site a few months ago, he finally got it working. It’s weird, but it can get on a network, and you can read Hackaday with it.

The entire computer is stuffed into a case that’s about 5″ wide, 4″ tall, and 10″ long. There’s a motherboard with built-in VGA, ‘game port’, and a printer port. There’s a riser card for real 16-bit ISA cards, two serial ports, and a connector for a hard disk and floppy drive. Basically, it’s an entire 286 system wrapped up in a tiny box.

After acquiring this machine, [glitch] took it apart and found the usual damage. The CMOS battery leaked, but not too bad. This was replaced with a hermetically sealed lithium thionyl chloride battery. These are non-rechargable, but a quick swipe of the soldering iron disable the motherboard’s charging circuitry. The hard drive was replaced with a 128 MB Flash module, and an Ethernet card was installed.

With that, [glitch] has a complete system that can connect to the Internet. Of course, getting on the Internet with a 286 is a challenge, but we have a Hackaday Retro Edition for just the occasion. The browser is Arache, with the mTCP package. That’s about as low as you can go in Intel-land, and excellent proof that the computer will work for another 35 years or so.

The PT2399 Delay/Echo Chip Data Sheet You Never Had

July 7, 2018 by Jenny List 13 Comments

If you are fortunate enough to have had the opportunity to play with an analogue-reel-to-reel tape recorder in a well-equipped studio, you probably looped the tape around to create an echo, or a delay in the audio. It was a desirable effect to have, but not a practical one for a guitar pedal or similar portable accessory. Silicon alternatives for creating delays have been in production since the 1960s, first the so-called bucket brigade delay lines that used a switched chain of on-chip capacitors, and more recently all-digital chips that process the delay by storing samples in RAM. One of the more popular of those is the Princeton Technology PT2399, but it comes with something of a snag for the experimenter in the form of a sparse data sheet. Thankfully the folks at [Electrosmash] have come to the rescue on that front with a thorough technical examination of the chip that should fill in any gaps in the official documentation.

After a brief examination of the range of chips of which the 2399 is a part, they dive right into the chip’s internals by rearranging the internal circuit diagram from the data sheet to the point at which it makes more sense. At which point the difference between the chip’s delay and echo functions becomes obvious, through the inclusion of a feedback path.

We then are taken through the pins, examining what lies behind the power supply and analog inputs and outputs. We are somewhere between a data sheet and an app note here, as some of this is information rarely present even in really good data sheets. Finally, we are taken through the chip’s performance, with real-world distortion and noise measurements. Armed with this page, the would-be PT2399 designer really can say they know what they are working with.

Surprisingly few PT2399s have appeared on these pages, however one did pop up in the Synthbike.

Smart Power Strip Revived With Raspberry Pi

July 6, 2018 by Tom Nardi 19 Comments

We’re all for buying broken stuff from eBay to save yourself a few bucks: buy it cheap, fix it, and reap the rewards of being a step ahead of the average consumer. Searching through the “For parts or not working” categories is nearly the official pastime here at the Hackaday Bunker. But buying an eBay find only to have it give up the ghost in a couple weeks? That hurts.

That’s precisely what happened to [idaresiwins] when he bought this beefy looking “Web Power Switch” on the Electronic Bay. After two weeks, the controller board blew and his “smart” power strip became very stupid indeed. But with the addition of a Raspberry Pi, he’s got it back up and running. Not only that, but given the extra horsepower this device now contains, it now doubles as a basic server for the home lab.

This conversion was helped by the fact that the original controller was on a separate board from the relays, and connected with a small ribbon cable. All [idaresiwins] had to do was figure out which wire in the cable went to each of the eight relays, and fire them off with the Pi’s GPIO pins. In an interesting detail, he opened up one of the ends of the ribbon cable and used it as a punch down block of sorts to easily hook the wires up to the Pi’s pins. We might suggest some hot glue to keep everything from moving around, but otherwise it’s a neat tip.

[idaresiwins] found some information online about making a web-based GPIO interface, which he adapted to control the outlets on the power strip. He then wrapped the Pi up in plastic to keep it from shorting out, and tucked it inside the case. Note that he was able to pull 5 VDC from the relay board and run it to the Pi over the ribbon cable, so he didn’t need to bother with hacking a USB adapter in there.

Controlling AC devices over the Interwebs is an extremely popular project, and we’ve even seen a DIY device that looks quite similar to this product. Most of them are now using the ESP8266, but with the Pi onboard this hack is more like a super-sized version of the PowerPwn.