In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Sparks-R-Fun wrote:

T'Saavik,

To a degree, less is often better when it comes to providing voltage to a regulator.  Unless you have a high efficiency one, most generate greater heat with higher input voltages.  This is a result of how they "regulate" the output voltage and in a sense turn the excess input voltage into heat.  So a nine or six volt input supply should generate less heat within a five volt regulator as there is less "excess input voltage" to spoil away.

As you increase the amount of power being used many unregulated supplies will actually drop their voltage level with an increase in electrical load.  (That is why they are called unregulated supplies!)  So with a light electrical load you could probably decrease your input supply voltage thus decreasing the heat generated in the regulator and still be fine.  As you begin to increase the electrical load within your development board you may find that your input supply begins to drop its voltage below the level that your regulator requires to function properly.  At that point, and especially if you are running servos, you may need to return to your 12V supply.

Please note that Parallax recommends the use of their 12V 1A supply!  So while the regulator may run warm for the reasons stated above and you might be fine using a smaller supply voltage if your circuits do not draw much current, you should certainly be all right with the recommended power supply levels.

 - Sparks

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