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In my campus i am using a power supply unit, in order to supply 5V and 0.02A, to my analog circuit that interacts with a microcontroller.

I am unable to go to the university because of work, and i want to take the circuit and the microcontroller to my house for programming work.

It's easy to carry the circuit that resides in a breadboard and the microcontroller, but i cannot take the big power supply.

So i want to provide 5V and 0.02 amps to the circuit.

I have never worked with power supplies before.

From a multi transformer i have in my house, i can get the voltage right. Heck, even USB proved 5V. I could solder some wires and provide supply to my circuit from the USB cable.

What i don't know is the amps. How will i be able to provide 0.02A to the circut?

Can i buy smoe power supply wit hthis value, or eevn varying amperes? Can i create a circuit that will amke sure i am supplying 0.02A?

user1584421
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2 Answers2

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Your circuit will draw what it needs, apparently up to 20mA. So any 5V supply will meet your stated requirement, provided it's capable of 20mA or more (see below).

20mA is a rather small current, so any decent USB charger will work, as will a power bank (with the advantage that you don't need to plug it in if it's charged). You just need to find a way to connect it.

If you have a sensitive analog circuit, there may be other requirements for noise, ripple, regulation, for it to work optimally, but for a typical microcontroller digital circuit, pretty much any such circuit will work.

Use a good quality supply with genuine safety markings, there are some really bad USB chargers out there that are actually dangerous. A spare power supply from an old brand-name router or switch would be a good possibility, and probably free.

Spehro Pefhany
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With rare exception, most circuits are arranged in constant-voltage mode. That means you supply them a constant voltage, and the circuit knows how to self-limit the current it draws so it doesn't burn up.

(History note: raw LEDs and raw fluorescent tubes are not like that, and incandescents are like that only due to herculean effort by Edison. Meanwhile, Tesla resigned himself to lamps requiring constant-current mode, and made transformers to do that; which Edison couldn't do because transformers require AC).

As long as your device is like that, you just need to get a 5 volt power supply. Let's see, you could order one from Mouser and have it in a wee--- just kidding, they're sold at every gas station and convenience store. USB blocks output 5 volts. Just get a USB cable and mutilate it to find the 5V and GND.

Harper - Reinstate Monica
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