By using a transformer without ct, a bridge rectifier circuit system, and rotary switch, we can create a power supply for electronic equipment with voltage range from 3 V, 4.5 V, 6 V, 7.5 V, 9 V, to 12 V.

Add component such a rocker switch or a slide switch as the main switch, and put one LED as an indicator tool.

Power supply circuit with variable voltage as shown below

Click to enlarge

Components are required:
  1. S1 = Rocker switch
  2. S2 = Rotary switch (2 pole 6 lanes)
  3. T1 = Step-down transformer without ct (220V/12V 500mA)
  4. D1, D2, D3, D4 = Diodes IN4002
  5. D5 = LED
  6. R1 = Resistor 220 Ω
  7. C1 = Elco (electrolytic capacitor) 2200 μF/16V


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