This is something I've been meaning to make for quite a while.
Basically the idea was that should you go around charity shops, car boot sales, yard sales, thrift stores and other such places it would be nice to have a power supply capable of giving you various voltages to check if things you are potentially going to buy actually work. the resistors are selected for 3 volts, 5 volts, 9 volts and 12 volts and you may notice that the resistor values (R2, R3, R4 and R5) are very specific and in some cases not available - these values are due to not being able to alter R1 when you switch the voltage.
there are 2 ways to get around this
1.add resistors in series or parallel eg. for R5 I put 2K and a 68r resistor in series and that was near enough to get me my 12 volt output
OR..
2. use 5K/4.7K trimpots and calibrate with your DMM - using that method you can of course easily set it for voltages you think you will need the most.
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Basically the idea was that should you go around charity shops, car boot sales, yard sales, thrift stores and other such places it would be nice to have a power supply capable of giving you various voltages to check if things you are potentially going to buy actually work. the resistors are selected for 3 volts, 5 volts, 9 volts and 12 volts and you may notice that the resistor values (R2, R3, R4 and R5) are very specific and in some cases not available - these values are due to not being able to alter R1 when you switch the voltage.
there are 2 ways to get around this
1.add resistors in series or parallel eg. for R5 I put 2K and a 68r resistor in series and that was near enough to get me my 12 volt output
OR..
2. use 5K/4.7K trimpots and calibrate with your DMM - using that method you can of course easily set it for voltages you think you will need the most.
