3D Printed Pogo Pin Programmer

April 6, 2015 by Brian Benchoff 21 Comments

The new hotness for Internet of Things hardware is the ESP8266. Alone it can connect to a WiFi network, but it doesn’t really have a lot of output options. Paired with an ATMega, and you really have something. That’s the philosophy behind the WIOT board, and when [Chris] was assembling these boards, he needed a way to flash firmware. The board has an unpopulated ISP header from the assembler, so pogo pins are the answer. How do you make a pogo pin jig? With a 3D printer, of course.

The ISP header wasn’t populated to give the board a slim profile, but this means a jig of sorts would be needed to program the WIOT. The first attempt was buying a few pogo pin adapters from Tindie, but this was terribly uncomfortable to hold while the board was being programmed.

To fix this problem, a small clip device was rigged up, printed out, and used for programming. Interestingly, this clip has a very deep throat, and a few holes used for bolting on a separate programmer. This shows a lot of forward thinking: the programmer can be reused for different boards with completely different layouts and programmers. If the next revision of the WIOT needs a JTAG header to program the micro, the problem of programming it is already covered.

How To Build A Thermocouple Amplifier

April 6, 2015 by Bil Herd 54 Comments

A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier circuit designed for the thermocouple being used.

Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier with Internal Capacitors — Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier
with Internal Capacitors

While researching “Zero Drift Amplifiers” as a follow-up to my video on Instrumentation Amplifiers I noticed the little schematic the front page of the LTC1049 datasheet which is shown here. I thought it was an ideal example of an analog application where some gain and some “gain helper” were needed to accomplish our useful little application of amplifying a thermocouple probe.

In the video I don’t really talk much about the thermocouples themselves other than the type I see most of the time which is type K. If you’re not already familiar with the construction of these probes you can find an informative write-up on thermocouples and the different types on the Wikipedia page and you might also want to check out the Analog Devices app note if you would like to know more. What I will cover is a reliable and precise way to read from these probes, seen in the video below and the remainder of the post after the break.

Continue reading “How To Build A Thermocouple Amplifier” →

Automated Die Testing

April 6, 2015 by Brian Benchoff 22 Comments

Are the contents of a Crown Royal bag fair? No, they never are. What about dice? In a quest for good randomness, [Apo] designed and built an automated die tester. Not only does it shake the die up, it captures images so real, actual statistics can be done on each individual die.

The setup is a n acrylic box made with BoxMaker attached to a 3D printed adapter for a stepper motor shaft. Randomizing the die happens exactly like you think it would: a stepper shakes the box, and a camera underneath takes a picture. With a bit of computer vision, this image can be translated into a number, ready for the statistics package of your choice.

There were only 559 rolls before the 3D printed mess of duck tape fell apart, but a test of the distribution revealed this die to have a 92% probability that it is fair. That’s not good.

Creating a cheating die is much more interesting, and to find out if he could do it, [Apo] stuck a die in an oven at 100° C for a few minutes. Surprisingly, the fairness of the die got better, suggesting it’s possible to correct an un-fair die. Putting it back in the oven after that threw the fairness out of the window but there was still no visual difference between this modified die and the original stock die.

More Power For Raspberry Pi USB Ports

April 6, 2015 by Brian Benchoff 56 Comments

Since the Raspberry Pi 2 was released, everyone building RetroPi emulators has been graced with four USB ports. For those of us doing useful stuff with the Pi, those ports are a little anemic: you can’t plug in a webcam and a WiFi module at the same time without suffering CPU brownouts. The maximum current all USB peripherals can draw from the USB port is 600mA. By changing a value in the /boot/config.txt file, this current limit can be increased to 1.2A for all four ports.

Pisquare — The yellow line traces the signal from the GPIO to the USB power switch.

Because the USB current limit is set in software, there must be a few bits of hardware that do the actual work. Tucked away below the right hand of the GPIO header is the hardware that does exactly that. It’s an AP2253 current-limited power switch (PDF), and the current is adjustable by tying a resistor to pin 5 on the chip.

Pin 5 on the AP2253 is connected to two resistors. One resistor goes directly to a ground plane, while the other is switched through a FET. The gate of this FET goes to another resistor, and when a GPIO pin is high, these resistors are wired in parallel. This means the resistance is halved when the GPIO pin is high, doubling the current limiting circuit in the AP2253.

This setup provides a relatively easy mod to increase the current limiting of the USB ports so they can provide 4x500mA, meeting the USB spec. The AP2253 power switch’s current limiting can be set by a single resistor, anywhere from 10kΩ to 232kΩ. By removing R50 and R4, and replacing R50 with a 10kΩ resistor, the current limiting of the AP2253 switch will be set to its maximum, 2.1A. Divide that by four, and you have 500mA per port, just like every other computer on the planet.

There is a reason the Raspberry Pi foundation set the current limiting of the USB ports so low. The Pi was originally intended to run off of a micro USB phone charger. There aren’t many phone chargers out there that will supply more than 1A, and the CPU and related peripherals will take half of that. If you’re going to change the /boot/config.txt file, you’re going to need a beefy power supply. Increasing the current limiting of the USB ports to 2A will require an even bigger, beefier supply.

Internet Of Cowbell

April 5, 2015 by Anool Mahidharia 15 Comments

If this is a sign of the times, the Internet of Things promises a lot of entertainment for hackers who can come up with wacky ideas and interactive projects. [Brandon] built a cowbell that rings when you tweet #morecowbell. Why? Because!

On the hardware side it is quite simple, and can be built in a number of different ways depending on the parts you have lying around. [Brandon] used an Electric Imp and its corresponding breakout board. A Sparkfun mini FET shield helps drive the solenoid that hits the cowbell. And because he had one lying around, he added a counter across the solenoid to count the number of times the Twitterati have rung the Cowbell.

The code for the Electric Imp consists of two parts – the “agent code” that runs on a server in the Electric Imp Cloud and the “device code” that runs on the imp itself – and is available at this Git link. Once you tweet with the hashtag, the Cowbell replies back, randomly selecting one from a list of stored responses. Would be nice to see a video of the Cowbell in action. And if it can be made to play the Salsa beat.

T-1000C: This Time The Chickens Will Be Back

April 5, 2015 by James Hobson 20 Comments

For whatever reason the city [Jenslabs] lives in decided it was a good use of taxpayer money to make some giant twig chickens and put them on the boulevard in front of his house. So he decided to spruce them up a bit with some electronics.

We’re still unsure why they did this, but [Jens] recognized them for what they truly are. T-1000C — the chicken edition. Giant robot chickens sent from the future to keep an eye on [Jens] to make sure he doesn’t stop ChickenNet. Naturally they needed glowing red eyes.

Fully expecting all his hard work to be thrown out eventually, [Jens] built the upgrades out of cheap components. A few LEDs, some transistors, resistors and a LDR (light dependent resistor). That way the eyes only glow at night. And to waterproof it all, he wrapped it in good ‘ol duct tape.

For more fun Easter hacks, why not add some LEDs to your decorated eggs?

Hackaday Links: April 5, 2015

April 5, 2015 by Brian Benchoff 36 Comments

[Dino] found something pretty cool at Walmart. It’s a USB Lighter; basically a car cigarette lighter that’s powered by a battery and charged via USB. A few bucks will buy you a battery, charge controller, and USB plug that will deliver over 2 amps at 3.7 Volts.

Speaking of battery chargers, here’s something from [Thomas]. He works in a hospital, and the IV pumps have a terrible charging circuit. After a few dozen chargers, they’ll give a battery error on the screen. They’re not bad, only unbalanced. [Thomas] made a simple rig with a Tenergy battery charger to rebalance the packs. No link, but here’s a pic. It beats paying $34 for a new battery pack.

Those Silhouette Cameo blade cutters don’t get enough respect. You can make vinyl stickers or an Arduino-themed pop up card.

Retroreflective spraypaint. Volvo has developed something called Lifepaint. It’s for bicycles and bicycle riders. Apparently, it’s clear when you spray it on, but if you shine a light on it – from a car’s headlight – it will reflect back. Any cool ideas here?

The Art of Electronics, 3rd edition, is finally out. Didn’t we hear about this a few months ago? Yes, we did. It’s shipping now, though, and there’s a sample. It’s chapter nine, voltage regulation and power conversion.

Ah, April Fool’s. I’m still proud of the Prince post, but there were some great ones this year. RS Components had Henry the Hover Drone, but we really like the protoboard with ground planes.

The market wasn’t always flooded with ARM dev boards. For a while the LeafLabs Maple was the big kid on the block. Now it’s reached end of life. If only there were a tree whose name ended in ~ino…