I apologize in advance for knowing practically nothing. I'm a programmer who has escaped the lab and really shouldn't be trusted with a soldering iron.
I have a USB Boarduino and I got it working with a single ShiftBrite last night. Now I want to hook up multiple of these and I know that the power coming from the USB port is not enough. I have a power adapter that can give me 5V at 2.6A which should be enough. But I don't know how to interface this with the Boarduino so that it is controlling the power output.
The instructables sounds like its telling the user to power the blinkM off of the voltage regulator on the arduino.
But yea tying the two grounds together will work.
10:47 < mage__> if I power a microcontroller off of 5volt supply A, and want to interface it with SPI to another chip thats powered by a different 5volt supply I just need to connect the two grounds together right?
10:47 < avrFreak> mage_ yes
That's right...attach all wires except V+ to the Arduino. Attach the external supply's ground to the Arduino's ground, attach the external supply's V+ to the V+ pin on the ShiftBrite. Should work! If you have problems with flickering, you may need to bridge the solder jumper on the bottom of the ShiftBrite, since you're using a 5 volt supply (but after that, never use it with a higher voltage). If you're able to find something like a 5.5 or 6 volt supply, the ShiftBrites will be a lot happier.