Can we connect to a 5V 20A power supply on a 5V 3A card?

Hello,
the whole question is in the title :wink: i think the answer is yes but i prefer to be 100% sure that it will not burn out or damage my card.
Thank you in advance for your answers!

An electronic device, such as an Arduino, will try to take as much current as it needs from the supply as long is the supply is capable of providing it. The fact that the supply may be able to supply more than required has no bearing on how much the Arduino actually uses

In fact it is good practice to use a power supply capable of providing more current than is required in order to maintain stability of the system and to prevent overheating of the power supply

1 Like

However a 20A supply will be less forgiving if you make mistakes like shorting things out. With 20A you will get enough current to vaporise PCB tracks, where as with a 1A supply mistakes will have less dramatic effects and you might even get away with them.

1 Like

I understand the point that you are making Mike but @mariecurry seems to need a 3A supply so a lower capacity supply would not be appropriate

Ideally the project would initially be powered by a current limited supply so that the current could be properly monitored and limited during testing

1 Like

Here is the standard answer.

My power point ("wall outlet", whatever you call it) is rated 240 V, 10 Amps, so it is clearly a "240 V, 10 Amp power supply".

I plug in my Ikea 240 V 3 W reading lamp. This device is then a 240 V, 0.0125 Amp appliance. What actually happens when I plug it in? :worried:

1 Like

That's all fine and good until an IC gets shorted by a miswire or IC failure, in which
case a 10A P.S. powering an LM555 with a shorted output can enable it to spontaneously ignite and burst into flames and glow red (melting the plastic solderless breadboard. (been there, done that) (more is better but too much is a recipe for disaster.) If you don't believe me, try it. (or not)

1 Like

Surely the suitably rated fuse that you have put into the circuit to prevent such problems will have blown long before such a disaster occurs

Also note the second paragraph of reply #4

1 Like

In the real world of amateur hobbyists, current limited supplies are rare, while in the
professional world , nobody would think of using anything but. Did you ask the OP if she even has one ?
Also, I didn't see any mention of a fuse by the OP.

1 Like

In the absence of current limited supplies what is your solution to the problem of matching the power supply to the current requirement of the project ?

You are correct. The OP didn't mention using a fuse and I should have included it in my first reply

1 Like

No, it will not burn out or damage your card, but it may burn out or damage your mistakes. :astonished:

1 Like

Fuses are really to stop the wires catching fire - semiconductors overload and burn out typically much faster than a fuse... The bond-wires on most semiconductor devices act as fuses too. Say you overload a 1A fuse with a heavy short-circuit, say 20A - the fuse vaporizes, the vapor arcs over and that 20A will flow for some time (millisecond or so perhaps) before the fireworks die down. So the fuse is needed, but not going to protect the circuit as much as you might naively guess.

1 Like

I could not not have said it better. I tried, and you're reply was much more elequent !