breadboard safety with 6V 3.5A power supply

by mightcouldb1 on Wed Nov 14, 2012 7:02 am

Hi there,
I am planning on buying a regulated 6V 3.5A power supply to power 2 servos drawing 300mA max current at 6V each.

I am new to external power so am planning on using the 2.1mm jack for the breadboard and hooking up that power supply directly to the breadboard.

I just want to make sure that I and my breadboard are safe to use that power supply if it is to power 2 servos (in parallel) together drawing 600mA current. Is there any risk of a current spike or supplying too much current since the power supply can send up to 3.5A? Will I need to use resistors?

Any help is greatly appreciated!
Best,
Jason
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Re: breadboard safety with 6V 3.5A power supply

by adafruit_support_mike on Thu Nov 15, 2012 5:05 pm

You shouldn't have any problems. A quick look through some datasheets says the 2.1mm jack will probably be rated for about 5A.

It's harder to get specific information about breadboards.. Wikipedia says they're rated for 5W, which the article interprets as 1A at 5v and 1/3A at 15v. I have a problem with that interpretation though, because power dissipation is measured in terms of the voltage across the component, not in terms of the supply voltage. To make the "1A at 5v equals 5W" thing work, you'd need a 5 ohm resistor. To make "1/3A at 15v = 5W" work, you'd need a 45 ohm resistor.

The actual resistance of a breadboard clip is usually a few thousandths of an ohm. If you send an amp through one, you shouldn't lose more than a few millivolts from one end of the clip to the other and the power dissipation will be a few milliwatts.

I'd say it's a good idea to stay below 2A in a breadboard, not because I expect the breadboard to blow up, but because you need heavier wire when you start passing serious current around. Once you go above a couple amps, the best wire to use won't fit in the holes any more.
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