Just a few additional components are needed to turn a Raspberry Pi into a DC voltmeter capable of reading up to 5 V and displaying the results in color on a monitor. The entire display area can be used, which makes the project an ideal basis for demonstrations, for example in schools.
 
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The program that accompanies this project is written for revision 2 of the Raspberry Pi in Python: a good three-part introduction to this language for people more used to BASIC has been published previously in Elektor [1]. There are two versions of the code. In both cases the Raspberry Pi communicates with an A/D converter chip using a small number of GPIO pins and displays readings on its screen.