using an AC Power Adaptor

[Pyromidion]

I've just bought an item that has a 9V 500mA requirement.

My local Radio Shack offers a 300mA and 800mA 9v adaptor, but not the 500 that my toy needs. Question is, would it be better to use the 800mA so that it's not straining itself, or would using the 800 burn it out?

-John

 

[Savij]

800 and add a resistor in parallel with the toy?

and try not to burn the house down.

You're going to destroy the toy either way.

 

[rockyct]

The item needs to draw 500mA, so anything equal to or greater than 500 mA. In this case, it's the 800 mA adapter.

 

[Jeff7]

Originally posted by: rockyct
The item needs to draw 500mA, so anything equal to or greater than 500 mA. In this case, it's the 800 mA adapter.

Exactly. The device will only take what it needs.

Using the 300mA adapter would overload it, and likely cause the adapter to overheat.


It's the same reason you can plug a 4W nightlight into a wall socket capable of delivering 20A (assuming the breaker trips properly) without any problems, or one of those EL "limegreen" nightlights that only draw a few microamps. The device only takes what it needs.


Voltage is a measure of how much the electrons "want" to move.
Amperage is more of a measure of how many electrons are available to do work.

So if you've got low voltage, but lots of amps, you will get a little bit of power flowing through, but could do so for a long time.
If you've got high voltage, but very low amperage (like an electrostatic spark), then you've got a few electrons that really want to move. But once they zzzzzt! move across, that's it. Done. There aren't any more available.

High amperage and high voltage is where you get the damage. Volts * amps = watts. More watts potentially (haha, get it?) means more capacity to do work. Or damage.

 

[chorb]

like it has been said, get the 800mA adapter. This will not burn out your item, the adapter can handle up to 800mA of current draw, but since your item only will draw 500mA that is all the adapter will give.

I doubt your item will work properly with the 300mA adapter.


If possible get a regulated output adapter (although I doubt the packaging will say). Something like this: http://www.sparkfun.com/commer...fo.php?products_id=298

 

[So]

Pyro, just in case you're not aware -- does your device need DC output or AC output? There are both types. Most devices need DC these days, but just check.