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.

A Constant Resistance Dummy Load Design

February 8, 2013 by Mike Szczys 21 Comments

constant-resistance-dummy-load

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.

PCB Production Workshop Means Everyone Gets An Arduino

February 7, 2013 by Brian Benchoff 3 Comments

nano

Over at the LVL1 hackerspace in Lousiville, [Brad] is putting together a workshop on etching PCBs at home. [Brad] wanted all the participants to take home something cool, so he settled on an Arduino clone as the workshop’s project.

The clone [Brad] used is the Nanino, a single-sided board we’ve seen before. Unfortunately, there aren’t any CAD files for the Nanino and doing a toner transfer with the existing PDFs was a pain. This led [Brad] to redraw the Nanino in Diptrace and put the files up for everyone to grab.

In his workshop, [Brad] is going to be using a laser printer, hydrogen peroxide, and HCl. one of the most common setups for home etching. If you’re in the Louisville area, you can make your own Nanino with a home etching workshop on March 16th. Be careful, though: those LVL1 guys are pretty weird; they have a moat and are building a homicidal AI.

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.

DIY Solder Stencils From Soda Cans

February 4, 2013 by Brian Benchoff 29 Comments

smd_stencil_done_w

Even if you’ve overcome your fear diddling about with tiny SMD components, applying solder paste – especially if you’re populating more than one board at a time – is still a chore. The pros use very expensive laser cut stainless steel solder paste stencils, something still a bit out of reach to the casual hobbyist. [Felix] solved this problem by making his own solder paste stencils very cheaply using empty soda cans.

The process begins just like any other home etching tutorial by lightly sanding the un-bent aluminum can and applying the etch resist via the toner transfer method. Etching is done with off-the-shelf HCl and hydrogen peroxide, resulting in an amazingly clean stencil comparable in quality with a professional stencil.

Sure, going through a dozen-step process to make a solder paste stencil may not be as convienent as [Cnlohr]’s toothpick and tweezers method, but [Felix]’ method is just about up to par with extraordinarily expensive laser cut stainless steel stencils. Not bad for something that came from the recycling bin.

Ammo Box PSU

February 3, 2013 by Brian Benchoff 30 Comments

PAB-PSU-1

Sometimes you need a power supply that can be thrown into the back of a car and taken into the field. [BadWolf] didn’t want to take his bench supply, so he whipped up this very portable power supply made from a computer PSU. To ruggedize his build a little, he put it in a 50 caliber ammo can making it more than able to handle the roughest field work.

While not a proper adjustable power supply, this ammo can is more than capable of delivering a whole lot of current in a number of different voltages. There are a few bells and whistles – a ‘plugged in’ and ‘on’ light, as well as a few very cool looking toggle switches that are sure to arouse the suspicions of unsuspecting bystanders.

[BadWolf] kept all the safety features built-in to the computer PSU, so this ammo box power supply is still protected from short circuits, and over-current, making it much safer than its appearance belies. It’s also a great example of what can be done if you don’t have a proper bench supply, so we’ve got to tip our hat to [BadWolf] for that.

Reverse Engineering Salvaged Part Footprints

February 1, 2013 by Mike Szczys 35 Comments

reverse-engineering-component-footprints

So you just pulled a fancy component off of a board from some broken electronics and you want to use it in your own project. What if the data sheet you found for it doesn’t include measurements for the footprint? Sure, you could pull out your digital calipers, but look at the measurements in the image above. How the heck are you supposed to accurately measure that? [Steve] found an easy answer for this problem. He uses microscope software to process an image of the board.

One common task when working with a microscope is measuring the items which are being viewed under magnification. [Steve] harnessed the power of a piece of free software called MiCam. One of its features is the ability to select an area of the photograph so serve as the measuring stick. To get the labels seen in the image above he selected the left and right edges of the board as the legend. He used his digital calipers to get a precise measurement of this area, then let the software automatically calculate the rest of the distances which he selected with his cursor.

MiCam is written for Windows machines. If you know of Linux or OSX alternatives please let us know in the comments.