Yes, that was very helpful. Thank you.

For my current projects, I forsee needing to create special power supplies
quite often. This will probably mostly involve putting together battery
packs, adding resistors or otherwise tweaking existing power supplies. Do
you (or any reader) know of a good source of education on this subject that
would focus on practice instead of theory? Basically I need to know how
long a battery will last a lot more than I need to know what a sin wave
looks like right now.


"Alexander" wrote in message
...

"B" schreef in bericht
news:sy%Ie.28780$HV1.4937@fed1read07...
I've read every electricity intro that I can find, but I still cannot
find the answer to one question about amperage:

Does a device (e.g. computer peripheral, 12 volts DC, one amp) use only
the amperage that it needs, or does it accept the amperage that it is
given. To put it another way, if I provided the above example with a
power source of 12 volts, *3* amps, would the device operate safely and
normally, or would the extra amperage overload it?

My instinct tells me that, knowing how amperage and wattage are related,
a device will only use what it needs. If that is the case, then a power
source with too much amperage will allow the device to operate normally,
safely, and for a very long period of time since it's using less power
than the power source is made to give. Nevertheless, I can't melt a
perfectly good piece of equipment because I refused to admit ignorance.

Your help is appreciated.

Brennan

Most PSU Power Supply Units Supplies a voltage, this voltage is stable on
the voltage given by the supplier.
If you have a 12V/1A Power supply, the voltage is stable to 1A load, if
you come above the 1A some might pull the voltage down others my overload
or shut down.
If you pot a 24 Ohms resistor to this PSU the cuurent drown form it will
be 0.5A because U=I*R.
So you can savely use a 3A PSU where you only need 1A.

One warning with this some PSU are really dedicated to one load and the
voltage will change if the load changes to much.

With the question you asked, the device must have a 12V Power Supply and
draws the current it needs. The 1A is the maximum under normal
operation/startup. So if you add more devices to one power source you
should add the Amps given and make sure the PSU can supply at least this
amound (if you use all the devices at once).

Hope this gives you more insight and answers your question,

Alexander