Electronic – What considerations should I have for high-current power supplies

power supply

I'm still pretty novice at electronics. I've recently been thinking of a project to make. The difference in this from my other projects is that for this I would need quite a bit of power. I'm use to using only a USB or battery powers supply. For this one though I think a PC power supply will be needed.

What precautions and considerations should I have when working with more amps(though the same amount of voltage)? If I hook an LED up to 5V, 500ma then it lights and works well. Will that be the same if I hook it up to 5V, 22A? What about for microcontrollers and other integrated circuits? Will they not be fried by the higher amperage?

If I do have something that does specify a max amperage rating, how do I decrease the amperage without affecting the voltage?

Best Answer

This is a pretty common mistake for people new to electronics. Most power supplies are designed to provide a constant voltage (5v in your case). Your circuit then provides a resistance of some sort, with microcontrollers and capacitors and such the resistance will change with time, but for beginners its usually best to think of your circuit has having a constant resistance as well.

So V/R=I, since V and R are constant, I will stay the same also.

The current that is given for your power supply is just the max that the power supply can output and guaranty a steady 5v. So if you work the V/R equation out and get 1Amp, then a 500mA power supply wont work for you, but a 22Amp supply will.

Sometimes this analogy helps people understand what is happening

Think of:

  • voltage as the height above the ground you are
  • current being the act of an object falling
  • max current as how much area you have to fall down in
  • an orange and an elephant as being 2 different circuits you have built

So if you have an elevator shaft that you drop an orange in from 100ft it will act the same (or close to if you ignore stuff like wind) as dropping an orange from 100ft off the top of the building. Now if you try to drop an elephant down an elevator shaft it will act much differently then if you drop an elephant off the top of a 100ft building.

So in the case of your original circuit (the orange) a 500mA max power supply (the elevator shaft) will act just the same as a 22amp power supply. (Off the top of the roof)

But when you go to your new circuit (the elephant) a 500mA max power supply will act much differently then a 22amp power supply.

Warning

A power supply that can output more current means that you have a greater chance of killing components if hooked up wrong. If you always hook stuff up correctly it wont ever be an issue, but I don't know anyone who has never accidentally hooked something up wrong.

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