D is 1N4001 diode or any of the same maximum current capacity. Fuse must be 0.5A, 250V or much lower amperage rating. Transformer is 220VAC to 26V -0 -26V, 2A or 120V to 26V -0 – 26V rating of 60VA or higher, bridge diode must be rated 3A or higher for good circuit operation. The resistors used are rated 1/2W.The input capacitor must be 4700uF or larger for better regulation and stability. The output capacitor Cout is 10uF.
This power supply uses LM317 for the positive regulation that can supply an output of 0V to 28V dc at a maximum current of 1.5A (with heatsink or cooling fan). The output voltage of the positive regulator is given by the formula:
Vout = 1.25(1 + 5K/240) + (100uA) (5K) - 1.4V
Where,
240 is the resistance from adjust and output terminal of LM317
5K is the resistance of the potentiometer connected to adjust terminal
-1.4V is the forward voltage of the two diode connection
Similar to LM317 operation, LM337 control the negative regulation of output voltage to ensure its output to 0V to -28V of a maximum current of -1.5A (of course wit heatsink). The variable negative output is given by the formula:
Vout = -1.25(1 + 5K/240) – (100uA) (5K) + 1.4V
Where,
240 is the resistance from adjust and output terminal of LM337
5K is the resistance of the potentiometer connected to adjust terminal
1.4V is the forward voltage of the two diode connection
Note: This power supply project is powered through 220V main and can cause electrocution
This power supply uses LM317 for the positive regulation that can supply an output of 0V to 28V dc at a maximum current of 1.5A (with heatsink or cooling fan). The output voltage of the positive regulator is given by the formula:
Vout = 1.25(1 + 5K/240) + (100uA) (5K) - 1.4V
Where,
240 is the resistance from adjust and output terminal of LM317
5K is the resistance of the potentiometer connected to adjust terminal
-1.4V is the forward voltage of the two diode connection
Similar to LM317 operation, LM337 control the negative regulation of output voltage to ensure its output to 0V to -28V of a maximum current of -1.5A (of course wit heatsink). The variable negative output is given by the formula:
Vout = -1.25(1 + 5K/240) – (100uA) (5K) + 1.4V
Where,
240 is the resistance from adjust and output terminal of LM337
5K is the resistance of the potentiometer connected to adjust terminal
1.4V is the forward voltage of the two diode connection
Note: This power supply project is powered through 220V main and can cause electrocution