Randy,
Do you have the LEDs picked out yet? If so, do you know any of the
electrical specs? Specifically you want to know the current thru the
LED and the forward voltage drop of the LED.
Typically a data sheet will list a maximum current (say 60mA) and a
nominal forward current (say 10-20mA) or one that they used to list
other specs like brightness. LEDs are current devices and you control
their brightness by how much current you allow thru them. Current
control is usually done by simply selecting a proper sized resistor
inline with the LED to limit current to whatever you need and below
what would damage the LED. If you hook up an LED to a power source
without a current limiting resistor, you will likely blow it.
LEDs have a forward voltage drop that tends to be related to color. For
example, typical RED LEDs have a forward voltage drop of about 2V or
so. I think White LEDs have a much larger forward voltage drop, like
3V-4.5V or there abouts. This is important because your voltage source
needs to be a bit higher than this to work with the LED and will help
you determine if you can hook up the 8 in series, parallel, or a
combination of both. As an example, let's say your White LEDs have a
forward voltage drop of 3.3V. If you took 8 and connected them in
series, this would be a total forward voltage drop of 8 x 3.3V = 26.4V,
so you would need a power supply of at least that, 28V being the
typical common size or maybe 32V.
So instead you might hook them up in a combination of 2 or more
parallel strings or a couple/few LEDs. As an example, if you used two
strings in parallel of 4 LEDs, this would be a forward voltage drop of
13.2V, so a 24V power supply would work. Or 4 strings of 2 LEDs so you
need a power supply of over 6.6, so a typical 9V or 12V supply would
work or even a nine volt battery could be used.
Anyway, back to your original question, yes, you would be best off
buying a small wall-wart type transformer from Radio Shack or somewhere
like that. Something about 9Vdc or larger would probably do the trick
and have a current rating of maybe 200mA or larger would be plenty. Or
you might look in your junk drawer at old chargers and transformers you
may already have for cell phones, radio controlled toy chargers, etc.
The specs (voltage and current) should be listed on the case.
Then the other thing(s) you will need are current limiting resistors,
but you first have to know what current(s) you are going to supply to
the LEDs so you can calculate what values and wattages you need.
To give you an idea, again using the 3.3V drop LED as an example and
say the LED is best run at 20mA and say you have a 12Vdc source.
Ohm's law is V=IR (voltage = current x resistance).
Power is P=VI (power = voltage times current).
For one LED off the 12V source at 20mA you have...
R = V/I = (12-3.3) / 20x10-3 = 435 ohms. Then you just pick a standard
resistor value that is in that ballpark (430, etc.).
Of course any errors I might have made above will quickly be corrected
by the rest of the group.
PT