Re:load, An Open Source Dummy Load

February 6, 2013 by Eric Evenchick 14 Comments

When testing power supplies or LEDs, a constant current dummy load is needed. These devices will draw a constant amount of current, regardless of the voltage at the input terminals.

[Nick] was looking for a load to test out a power supply, and found commercial offerings to be too large, too powerful, and most importantly, too expensive. This lead to the design of the Re:load, his open source alternative.

Like other constant current sources, the Re:load uses an opamp to control a pass element. While most constant current loads will just use a transistor, [Nick] opted for a BTS117 smart low side switch IC. This device has a built in current limiter, over-voltage protection, over-temperature protection, and short circuit protection, which makes it much safer. The project write up goes into detail on how the device works.

If you need a constant current load, [Nick] is selling kits on Tindie. All the design files are available on Github so that you can build your own.

Y Combinator And Upverter Host Hardware Hackathon

February 1, 2013 by Eric Evenchick 2 Comments

Startup accelerator Y Combinator and Upverter are joining forces to run a hardware hackathon. This event aims to encourage hardware hackers to get together and design new products in a twelve hour sprint. Startups including Pebble, Octopart, and Lockitron will also be participating.

It’s a free event, and the winning teams will get their design manufactured. Participants will retain the rights to their designs, get free professional Upverter accounts, and have the chance to chat with some of the Y Combinator partners. This makes it a great opportunity for people looking to create their own hardware startup.

The event takes place on February 23rd at the Y Combinator offices in Mountain View, CA. Registration is open until February 8th. If you’re in the Bay Area and do hardware, you should check this event out.

The Keypad Contest

January 31, 2013 by Eric Evenchick 11 Comments

What can you do with ten buttons and ten lights? A lot.

[Andrew] and [Nathan] found a collection of Hale Research keypads being thrown out, and decided to host the Keypad Contest. The goal of the contest was to create something nifty using the ten buttons and ten lights on the keypad, and an ATtiny2313 that replaced the original 8051-compatible microcontroller in the device.

[Andrew] wanted to try making PCBs with his home-built CNC machine, so he milled out USBtinyISP programmers for the ATtiny2313. Then he gave out eleven development kits to a group, and explained how to develop on the hardware.

After a month of hacking, seven people completed projects. The winner was an internet radio controller, which had the keypad sending serial data to a TP-Link WR703N router. The router used a USB sound card and OpenWRT firmware to stream music. The runner up was a timing game called “Capture”.

The contest write up has details on all seven projects. [Andrew] and [Nathan] were successful in getting software engineers to try hardware with this contest, resulting in some neat hacks. After the break, check out a video demo of the internet radio controller.

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Automated Doors For Theatre Effect

January 30, 2013 by Eric Evenchick 15 Comments

For a theatre production, [Jason] needed a way to automatically open and close doors as a special effect. His solution, hosted on Github, lets him remotely control the doors, and put them into a ‘freak out’ mode for one scene in the play.

Two Victor 884 motor controllers are attached to an Arduino that controls the system. A custom controller lets [Jason] actuate the doors remotely, and LEDs are used to display the state of the system.

On the mechanical side, two wind shield wiper motors are used. These are connected to custom arms that were printed using a Lulzbot AO-100. The arms allow for the door to be automatically actuated, but also allow for actors to open the door manually.

The result is a neat special effect, and the 3D models that are included in the repository could be useful for other people looking to build automated doors. In the video after the break, [Jason] walks us through the system’s design and demonstrates it in action.

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Duct Tape Bagpipes

January 29, 2013 by Eric Evenchick 37 Comments

Looking to build your own instrument out of plumbing and tape? [Scott] made his own set of Membrane Bagpipes out of PVC pipes, a plastic bag, and duct tape.

Bagpipes are made out of a few parts. The drones are pipes that are tuned to play a single note. They are tuned by the fixed length of the pipe. The chanter is a tube with finger holes. This lets you play various notes depending on which holes you cover. The blowpipe is used to fill the bag with air that will pass through the membranes on the drones and chanter. Finally, there’s the bag which stores air.

[Scott]’s build uses PVC for the drones and chanter. The membranes are made out of cut up bits of plastic bags. Some crafty duct tape work makes up the bag, and seals it on to the various parts. A check valve is used to stop warm, duct tape flavoured air from blowing back into your mouth.

It’s pretty amazing what people can do with a few rolls of duct tape. The pipes aren’t exactly in tune, but they certainly work. Check out a video of them in action after the break.

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Vintage Kegerator

January 23, 2013 by Eric Evenchick 25 Comments

[Kerber] got his hands on a classic 1950’s General Electric fridge, and converted it into this classy vintage kegerator.

As his build log shows, it took an intensive restoration process to get this fridge back in shape. He completely stripped it down, scraping off the sixty year old insulation, fibreglass, and glue. Then the chassis was sanded down to a smooth finish and painted black. R-19 insulation was added to replace the old stuff.

Next up was electronics. An Arduino, DS18B20 temperature sensor, and a solid state relay were used to regulate the temperature and prevent frozen beer. There’s also a Guruplug server that reads data from the Arduino every minute. It makes this data accessible through a web page, so the temperature of the kegs can be monitored from anywhere. [Kerber] admits that this is overkill, but leaves room for future expansion.

The kegerator draws about 180 Watts, and runs for about 6 minutes per hour to keep the temperature regulated. This is pretty impressive considering the age of the fridge. The final restoration looks great, and serves up data along with the beer.

How 6502 Overflow Works

January 15, 2013 by Eric Evenchick 16 Comments

The 6502 was a ubiquitous microprocessor back in the 80s, powering devices such as the Apple II and the Nintendo Entertainment System. [Ken] took an in depth look at a small part of the processor: the overflow circuit.

In order to do signed calculations, a microprocessor’s arithmetic logic unit (ALU) needs to be able to calculate when an overflow occurs. This happens when two numbers are added that cannot fit in a single byte. The result of a calculation will be incorrect, so the processor must inform the program that an overflow has occurred. This is done by setting an overflow flag.

[Ken] uses this example to first explain how the overflow circuit works in logic. He then looks at the gates and a transistor implementation of the logic. Finally, he walks us through the circuit on the actual 6502 die, showing how the circuit is constructed in silicon.

This is a great example to learn a bit more about how ALUs work and how integrated circuits get built.