Cheap Power Supply
From LA Biohackers
One essential piece of equipment for a molecular biology lab is the electrophoresis power supply. This page describes a cheap way to build a minimalist 60V electrophoresis power supply. It will require a small amount of soldering, but it will be super cheap.
- 12V power adapter, 1.5A minimum
- 60V boost converter
- Small plastic project box
- 2 banana plugs
- 1 coaxial power connector
- 1 toggle switch
- 4x Round 6x32 screws (the kind for mounting hard drives)
- A few inches of stranded wire
The 60V boost converter can be found for around $10 on eBay. See the photograph on the right. It uses 12V as input and generates 60V. I would link to the eBay page but it will break every few days. If you don't like eBay, here is a similar product from a different website, for $17.
To mount the boost converter onto the project box you will need 4 6x32 screws. These are the ones used to mount hard drives or optical drives in your computer so you may already have a bunch laying around.
12 Power Adapter
You probably already have a 12V power adapter. It needs to have the appropriate AC input for your region. It needs to have 12V output and be able to supply at least 1.5A. If the 12V adapter lists the specifications in terms of watts instead of amps, it should be at least 18W. It will probably have one of these coaxial power connectors. The tricky part will be finding the right female plug to match your specific coax connector. They come in different sizes so you will need a specific size plug. The best method might be to take your adapter to a local electronics shop and try them out. If you don't already have a suitable power adapter, here is one for $8, before shipping.
Project Box - minimum 12x6x4cm (LxWxH)
|12V power adapter||8.00|
|60V boost converter||10.00|
|2x Banana jacks||1.33|
If you already have a suitable power adapter, the total cost will be 15.06 USD, before shipping and tax.
- Soldering Iron
- Wire stripers
- Wire snippers / scissors
- Power drill
First make sure you have all of the necessary components. You should have a project box, 2 banana jacks, 1 coaxial power connector, 1 power switch and some stranded wire.
The next thing to do is measure the diameter of your banana jacks, coaxial power connector, and power switch. You will need to drill holes in the chassis large enough for the barrel of the component to pass through but small enough that the rest of the component cannot. I chose to drill the hole for the power connector on the back and the banana jack and power switch holes on the front. You will also need to drill 4 holes on the bottom of the box to screw the circuit board in. They need to form a rectangle measuring 27x58mm. To make things simple, print out this PDF and poke holes through the blue circles. Use it as a guide for drilling the holes.
Now cut two pieces of wire, each two inches long. With each piece of wire, strip both ends then solder one end onto one of the banana jacks. You can see these on the left side of the middle image below. These two wires will eventually be connected to the outputs of the circuit board. Now cut three more pieces of wire 2, 3 and 4 inches long. The 2 inch wire will connect the power jack to the the power switch, the 3 inch piece will connect the power switch to the circuit board, and the 4 inch piece will connect the power jack straight to the circuit board.
Your power jack will probably have 3 connectors: 2 which connect to the barrel and 1 which connects to the center pin. Use the 2 inch wire to connect the negative (barrel) to the switch. Then solder the 3 inch wire onto the other end of the switch. This 3 inch wire will eventually be connected to the negative input of the circuit board. Now solder the 4 inch wire onto the positive (center pin) of the power jack - the other end will eventually be connected to the positive input of the board.
Now connect the wires to the screw-mounts of the circuit board. To connect the wire, first use a flat-head screwdriver to loosen the screw on the top of the terminal, insert the wire into the side of the terminal and re-tighten the screw.
The 4 inch wire connected to the positive terminal of the power jack should go into position #1 (see image below). The 3 inch wire coming from the switch should connect to position #2. the black (negative) banana jack should connect to position #3. The red (positive) banana jack should connect to position #4.
Once all the wires are attached to the circuit board, screw the board down to the box. After the board is screwed down, mount the power jack, switch, and banana jacks to the box. Depending on the size of your box and the thickness of the wires, you may need wrestle with the wires to get them all inside.
Before closing the box, use a flathead screwdriver to turn the potentiostat all the way counter clockwise to set the circuit to boost to 60V. Now plug in your power adapter, connect your gel box and run a gel.
For a simple sanity check, make sure the electrode connected to the black (negative) terminal is generating approximately twice as many bubbles as the red (positive) side.
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