Building A Tool To Measure Melting Point

February 8, 2013 by Mike Szczys 5 Comments

melting-point-apparatus

When working with chemical reactions it may be necessary to test the purity of the components you’re using. This is especially true with hobby chemists as they often acquire their raw materials from the hardware store, garden center, or pool supply. [Ken] figured out how to get around the $500 price tag of a commercial unit by building this DIY melting point test apparatus.

In this image he’s using a thermocouple to monitor the temperature of the melting surface, but mentions that you can do this with an inexpensive dial thermometer and will still have great results. That melting surface is the hexagonal head of a bolt which he drilled out to provide a concave surface for the test compound. Inside the PVC pipe is the heating element from a 40W hot glue gun. He wrapped it in fiberglass fabric which is sold in the plumbing supply to protect the area around pipe joints during soldering. The rotary light dimmer feeds the electricity to the element, allowing for adjustments to the ramping speed.

Raspberry Pi Is Right At Home Inside Of A Game Boy

February 8, 2013 by Mike Szczys 17 Comments

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[Matt] still has his original Game Boy from when he was a kid. He wanted to pull it out and play some of the classics but alas, the screen was broken and he couldn’t find a source for a drop-in replacement. In the end he ordered a used unit and pulled the screen from that one. This left him with a pile of leftover Game Boy parts which turned into a Raspberry Pi case project.

Since the RPi doesn’t have a power switch he thought it would be pretty neat to incorporate the Game Boy power switch. He was able to cut out one section of the original PCB that included the switch and one mounting hole. This kept the switch aligned with the case and gave him some pads to solder the incoming USB cable and the jumper wires to the RPi board. In the image above the power LED is on. He mentions that there was an issue with that circuit; the voltage drop across the LED was messing up the feed to the Pi so it’s disabled for now.

We’ve embedded a couple of images of everything inside the case after the break. If you’re a fan of this hack you should also take a look at the Game Boy hard drive enclosure which uses the same pixel art printed on paper effect for the screen window.

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3D Printed Prosthetic Hand Helps Out For About $150

February 8, 2013 by Mike Szczys 26 Comments

3d-printed-prosthetic-hand-on-thingiverse

We know that there are already 3D printed hips and knees in use in the medical field, but it takes a story like this one to really bring home the idea of how this technology changes lives. 5-year-old [Liam] is missing parts of his right hand, and this open-source prosthetic hand has given him a jolt of increased function. The video clip after the break shows him on the third day with the device. He’s practicing picking up coins from a stack using the hand. Just $150 in parts, combined with the hard work and good nature of the developers, made this possible.

The design is available on Thingiverse. In addition to the 3D printed parts the prosthesis uses off-the-shelf hardware store items like bungee cord and fasteners. The tips of each finger and the thumb are given some flex and grip by covering each with a rubber thimble.

We love seeing this life-changing technology wielded by basement and garage hackers. Another great example is this scratch-built leg from last May.

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A Constant Resistance Dummy Load Design

February 8, 2013 by Mike Szczys 21 Comments

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This constant resistance dummy load has not yet been tested in the real world. [YS] was inspired to come up with the circuit after reading Wednesday’s Re:load dummy load post. That was a constant current load, not a constant resistance load. [YS] started with the schematic for the Re:load and made his changes to arrive at this.

For him the exercise was just to alter the design to achieve constant resistance. He didn’t actually build and test the hardware because he doesn’t really have a need for it. This image was exported from Proteus, which includes a ProSPICE circuit emulator. His slides run through test voltages from 5V to 50V, maintaining a constant 10 Ohm resistance.

When studying this project we needed a little refresher on the different varieties of dummy loads. We found this post very informative about the differences and uses of Constant Current, Constant Power, and Constant Resistance (Impedance) loads.

Learn Shift Registers Without Involving A Microcontroller

February 7, 2013 by Mike Szczys 14 Comments

This is a truly hands-on approach to learning. [Kevin Darrah] ditched the microcontroller and is using push buttons to learn about 595 shift registers. The test rig uses two of the serial-in, parallel-out chips. These are cascading which means that as data from the first chip overflows it feeds the input of the second. The parts are commonly used to drive LEDs, or reduce the number of pins needed to drive peripherals like this character LCD.

The five push-buttons give you a chance to intuitively learn how the chip logic works. The blank button is also commonly called Output Enable (OE). Driving it high shuts off the outputs of the chips but doesn’t clear the data. That task is performed by the clear button which is driven low to set all of the shift register memory to zero. The other three buttons set the logic level, shift it into the chip using the clock signal, and push the stored values to the outputs using the latch.

To get a visual approximation of what’s happening inside of these chips you should check out the shift register tutorial linked to in this post.

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USB Apple ][ Disk Emulator

February 7, 2013 by Brian Benchoff 14 Comments

One of the most commonly frustrating things about having an old Apple ][ lying around in your basement or attic is the lack of software. While at one time in the late 80s you may have had your own copy of Oregon Trail, that disk is either lost or non-functional, and it’s pretty hard to get new disk images onto 5 1/4″ disks.

To solve this problem for himself, [Eric] came up with an Apple disk emulator. A project like this has been done many, many times over the last few decades, but [Eric] put his own twist on it: he doesn’t use a microcontroller. Instead, he used a simple USB FTDI device to talk to the Apple disk drive.

The FTDI device in question is a UM232H chip that takes a USB connection and turns it into an SPI bus. Of course the Apple ][ disk doesn’t speak SPI, so [Eric] needed to do a little logic conversion with a 74LS251 multiplexer and a 74LS161 counter.

In the video after the break, you can see [Eric] loading Apple disk images on a IIc from his new Intel Mac. It’s a neat build, but it’s not done yet: [Eric] plans on adding a microcontroller with an SD card, allowing just about every Apple ][ game every made to fit in your pocket. Yes, [Eric]’s project is quite similar to the A][ pocket serial host we saw just a bit ago, but this will hopefully have a lower component count.

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Add Motorized Blinds To Your Home Theater

February 7, 2013 by Mike Szczys 20 Comments

motorized-blinds

[Chipsy] found himself with an interesting problem. The room that serves his home theater has a wall mirror which reflects part of the screen during viewing. In an otherwise dark room this was very distracting. His solution was to add a blind that covers the mirror during viewing, but who wants to constantly pull that down and back up again? Since the motorized projection screen he is using has a remote control he figured out a way to motorize the blind and synchronize it with the screen’s remote.

The screen uses mechanical relays to switch the motor. He patched into these with an Arduino to detect whether the screen was going up or down. It was easy enough to use his own relay and motor with the blind, but he needed a way to stop the blind once it was in position. For covering up the mirror he simply sets an 18 second timer, but for retracting the blind he wanted precise alignment so he added a magnet and sense its position with a reed switch. See the synchronized screen and blind in the clip after the break.

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