Stepped Desktop Power Supply
Most of the times a fixed voltage power supply is very much required for quickly connect and test an electronic equipment. Having bi-polar (both positive and negative) DC power supply is added advantage for working with op-amp circuits etc.
The circuit of Stepped Desktop Power Supply is simple and easy to construct. The input should be in between -18VDC to -21VDC for negative output voltage power supplies -3VDC, -5VDC, -8VDC, -12VDC & -15VDC. Similarly, the input should be in between +18VDC to +21VDC for positive output voltage power supplies +3VDC, +5VDC, +8VDC, +12VDC & +15VDC.
All the output Voltages are generated using fixed voltage regulator ICs, 7805, 7808, 7812, 7815 for positive voltages and 7905, 7908, 7912 & 7915 for negative voltages. For +3V, adjustable positive regulator IC LM317 and for -3V, adjustable negative voltage regulator IC LM337 are used with resistances 330Ω and 220Ω for fixed voltage outputs.
Refer full circuit diagram:
Two berg strip sets are used on the PCB, for Positive and Negative Voltage outputs separately, for easy connection as per individual's requirements.
GOOD LUCK. ENJOY.