General DC Power Question

[semaj4712]

If I bought for example this Power Converter to go from AC to DC...

http://www.voltage-converter-transformers.com/product_info.php?category_id=10016648&products_id=10061388

And for example I wanted to test a car radio off of it, and the car radio is rated for 7.5 amps...If I ran a fuse in the positive line before the radio that is 7.5 I would be fine and wouldn't need to worry about the fact that the converter is 20 amps...that way I can use it for a wider variety of applications.

Can I do this or am I missing something?

[IP2GSR]

You are on the right track for sure. I would not rate the fuse at exactly the current drawn by the radio. As an example if the radio draws 7.5 in your example rate the fuse at 10A so that it would allow for short current spikes that may happen like when you first turn it on. If it has a CD then the motor loading mechanism will draw a short current spike as it loads.

The supply is rated for 20 amps but it will only put out what is required by the radio. If that is 2 amps so be it. If you crank the volume or do some other function that requires more power say like 5A then the supply adapts and puts out 5A all while keeping the voltage very close to +13.8V.

[semaj4712]

Ah ok that makes sense, thanks man for the info

[IP2GSR]

Ah ok that makes sense, thanks man for the info

I should add that a power supply salvaged from a desktop computer will have a +12V output that will supply upwards of 12 to 15A. You could use that as well. Those supplies like to have the other outputs loaded as well (+5, +3) but most times it will work fine.

Since the battery voltage is about 12.5 Volts when the car is off most all radios are designed to work with a voltage that low.

A salvaged supply is cheap or free but will not be as stable or low noise as the one you linked to.

:D

[semaj4712]

Gotcha cool man thanks