This tutorial explains how to make your own power supply unit for all your electronics andembedded system experiments. It also has a backup battery which will be used in case of power cuts and a display.
1. SLA 12V battery
2. Banana Jack connectors female (2 pairs each)
3. Screw Terminals (1 pair)
4. SPST switch (ratings 5A or more)
5. Adjustable Voltage Regulator LM317 x 2
6. Voltage regulators 7805, 7809, 7812
8. Step-down Transformer 16-18V/3 Amps
9. 1N4007 Diodes x 4
10. Two Relay Module
13. ATmega16/8 Development board
14. 16×2 LCD
15. Heat Sinks
– Inputs: 220-240V, 50Hz AC
– Outputs: 1 X 5V and 1 X 9V (available through banana jack)
1 X Adjustable voltage (available through screw terminal)
– Adjustable Voltage Range: 1.25-14.5V in Mains Mode and 1.25-10.5V in Battery Mode
– Modes: 1) Battery Mode and 2) Normal Mode (Through Mains)
– Automatic Switching and Shutdown by Microcontroller
– LCD with various indicators.
Blue line indicates signal lines and black lines indicate power lines.
Let me explain you what each block consists of and its function.
Mains Block: This consists of the transformer, bridge rectifier (4 diodes) circuit and a capacitor. This block takes in the power from a wall socket which provides 220-230V AC. The step-down transformer scales down the amplitude of the sine wave, followed by the bridge rectifier which converts it into pulsating DC which when passing through capacitor yields a unregulated DC power of 16-18V (voltage depends on transformer)
Charger Circuit: This block mainly consists of an adjustable voltage regulator LM317 which along with other components works as constant voltage, current limited charger for our battery. Once the battery is full charged, the circuit automatically supplies low current to the battery and goes into trickle charging mode.
For more detail: Un-interruptible Bench-top DC Power Supply With Display