heres a question about an external supply i found at the thrift shop for a buck.
it says on it that it is an 11 volt 2 amp power supply. dc.
when i hook it up to the multimeter (when it isnt attached to anything but itself) i get a reading of 14.23 volts. i am looking for a supply that will run three arduinos...the arduinos in turn are running many optocouplers, switches, relays, multiplexers, and are sensing to all get-out across the board (pun intended). im thinking each will be drawing(requiring) in the ballpark of 600 mA of 5 volt goodness.
my question is this-- will this 11 volt supply that reads 14.23 volts fry my boards...? or will this voltage drop as i connect the supply to all three boards at once and make it into the safe zone of operation suggested by the manufacturer of 12 volts or under?
i hooked up a 7 volt that supplies 2 amps to the three arduinos and the third one got a little
schiztzy after the hookup and the multiplexing turned unreliable.
will i need, most likely, a 9 volt 2 amp supply?
or will this 11 volt most likely work for me?
also, if the 14 volts is a problem, could i retrofit some additional heat sinks on the 7805 so it doesnt cook my board and still use it?? i love this wall wart---its perfect---id love to paint it with acrylics and install it with indian beads. no seriously.---if this one aint a gonna work , ill look for the right one. any suggestions on what the right one could be? or perhaps you can advise me of a way to use the one i found for a buck.
thanks a bunch
arduiYES
An unregulated wall wart will always read a much higher voltage when there is no load connected. So your experience is very typical. When attached to a load like your Arduino (even this small load), it should read 11V. This is suitable for powering an Arduino, but since it is at the high range (7-12V), the voltage regulator on the board may be quite warm, especially if your project draws a fair amount of current.