A variable bench power supply can be used to power all your electronics project - without having to mess with batteries of different voltages, and accompanying battery holders.
Parts of power supply
The above power supply can power three independent circuits.
- v1 can vary from 0-30V DC (max 3A)
- v2 can vary from 0-30V DC (max 3A)
- v3 can output a fixed 5V at 3A
To connect the power supply to the circuit you use special wires that have a banana plug terminals on one end, and the alligator clips on the other end. The banana plug plugs right into the power supply.
By convention, you connect the RED cable to positive, and the BLACK cable to negative. The alligator clips will connect to your circuit.
How to use a bench power supply
Before you use the power supply, you need to know two things - how much voltage do you need, and what’s the maximum current your circuit can handle, without it’s components melting away.
Got that? Good. Now proceed with the steps below:
- Press the power on/off button and turn it ON.
- Rotate the voltage dial to the voltage you need. It’s very sensitive; turn slowly.
- Connect the RED and BLACK cables.
- Now connect them together by snapping the alligator clips to each other.
- Rotate the current dial to set the maximum current you want.
- Disconnect the alligator clips and now connect them to the circuit.
Be careful not to move the voltage and current dials when the circuit is working; doing so might blow up things!
Anything less than 9V and 10mA is probably ok, but anything higher than that needs careful thought.
Your skin has a lot of resistance - 10,000 ohms or so if it’s dry. So if you’re playing with about 20V, it will not push much current through your body. In this case, it is 20/10,000…abour 2 milliamps. You will not feel it. This is why you can hold a 1.5V battery in your hands and no current will flow through you, even through the 1.5V volt battery can put out a large current in a circuit that has, say, 1.5 ohm resistance. (1.5V/1.5R = 1A)
But if you skin is wet, the resistance goes down rapidly. It can even go down to 1000 ohms, which means the same 20V is now pushing 20 milliamps of current through your body. That’s too much current. This page has a chart on how current flow can affect your body. You want to stick to AC-1 and AC-2 zones.
Avoid water at all times when working with electricity. Wet hands? BAD idea! This is the number one rule for electrical safety.
Additional safety guidelines
Never ground yourself when working on your circuits. Keep your body isolated from ground by using dry clothing, rubber shoes, rubber mat or any other insulating material? Why is this important? Well, if you’re not insulated, it means you’re a conductor. And that means, electrons will flow through your body if you make a mistake. The bench power supply can provide sufficient current to harm you.
Never touch exposed wiring, or connections when working on a live circuit.
Use rubber gloves.
- Is there ever a time when you have to connect all three terminal - positive, negative and ground?