I always seem to get confused when dealing with voltages and power supplies.

I have been told that as long as the Voltage is higher than you need and the amperage is what you are looking for you are OK but it always scares me when I see something that say 19V and all of my info says 12V. Please correct my thoughts if they are incorrect and give me an easy way to remember what I need to look for.

Thanks
Jeff

 

#12 has got you covered...

 

You supply the rated voltage for your design application, so if say the circuit requires a 5V supply, then do so otherwise it will take more current than it needs to and may blow up.

As long as the input to the psu is higher than its regulating down to your ok.

 

You've actually got it backwards. In general, it's alright if the power supply has a higher current rating, so long as it has the correct voltage rating. The only catch is that some power supplies (Typically unregulated ones) will actually output slightly higher voltage than you'd expect under lighter loads than it was designed for, this is because they are rated at their expected load, and at different loads the voltage drop will be different.

 

I always seem to get confused when dealing with voltages and power supplies.

I have been told that as long as the Voltage is higher than you need and the amperage is what you are looking for you are OK but it always scares me when I see something that say 19V and all of my info says 12V. Please correct my thoughts if they are incorrect and give me an easy way to remember what I need to look for.

Thanks
Jeff

A mentioned, you want to keep the voltage very near the specified voltage. Current is a different matter. The required current is drawn by the device. If your device requires 12 volts DC at 1 amp, The power supply should be rated at 12 VDC 1 amp or higher. If the power supply is rated at 12VDC but at much higher current, say 2, 3 or more amps, that's fine.
The device needs the voltage specified, but only draws the current it requires.

EDIT: If using non-regulated wall-worts the current rating should be kept just a bit higher (maybe 20%-50%) than required, because if the current rating is a lot higher than required the voltage can rise considerably.