Archive for June, 2010

Discount Glassware

I recently purchased a lab’s worth of glassware from Ginsberg Scientific on Amazon for about $70. The individual pieces are as follows: Griffin beakers, one 50ml, two 250ml and one 600ml — Erlenmeyer flasks; one 50ml, two 250ml and one 500ml –six medicine droppers — six stir rods 6″ — one graduated cylinder 10ml — one graduated cylinder 100ml — one serological pipet — twelve test tubes 16x150mm — one short stem funnel 75mm x 75mm. All (with the possible exception of the eyedroppers) are of Bomex borosilicate glass and are resistant to thermal shock. I hope to be using these soon.

How to Make a Power Supply

Power is needed for many processes and reactions, but DC current at the right voltage can be hard to come by. If you have an arc welder or a car charger then that’s great, but if not then you can just convert a computer power supply.


Computer power supply, multimeter, binding posts, soldering gun, solder

1. First, find a computer power supply (technically modifying and not making). You can get this from any old computer, some might be better than others; but I wouldn’t count on it. I would check the dump, but you could also look on Craigslist and eBay. The binding posts are not strictly necessary, but they make it neater and only cost a couple dollars at Radio Shack.

2. Crack it open with a screwdriver to reveal the wires. Cut off the plugs and wire ties (making sure to leave the power to the fan).

3. Drill holes into the side of the supply and attach the binding posts. It’s a good idea to label the voltages of each binding post.

4. Sort the wires by color. The different colors for mine are: black-ground, orange-3.3V 17A, red-5V 22A, blue-5V 22A, White- 12V 18A, yellow-12V 18A, brown-sense wire, green-DC on (for adding a switch), grey-power on (for adding an on-off LED. I only used the orange, red, and white wires because the yellow and blue wires have the same voltages and I saw no point in adding a switch or indicator light. In my power supply there were different shades of blue and orange but a test with a voltmeter revealed that the voltages were the same. If you can find wires with opposite voltage (+/-) then be sure to use them, as they will double the voltage between them.

5. Tape the wires together by color, cut all of the ends to the same length, strip the last inch or so, and solder them to the binding posts. It may be helpful to leave a single wire longer, solder all of the other wires to it, and solder it to the binding post. Make sure that you solder the brown sense wire to the 3.3V orange wires or else the power supply will not run.

6. Tape off all exposed wires, reassemble it, and find a use for your converted DC power supply. Make sure not to short out the wires because that will trip an internal safety and it won’t work for several minutes.

If you want to add a power switch or indicator LED then take a look at this.