Digital DC Power supply using PWM and PIC

In our lab I saw many DC power supply which have a variable knob to regulate the output. I was dreaming to make such a project where I can regulate the voltage using push button.As I am not an industrial level expert so this project is just about a digital DC power supply of small range(5V-12V). You can press push buttons to increase or decrease output voltage.Here we use LM317 to regulate the output voltage. Output voltage is controlled by the PWM output of a pic microcontroller.An OP-AMP is required to amplify the PWM output level. The idea is simple and easy to implement in circuit.

Necessary Software:

1. Proteus 7.8 Professional
2. MicroC Pro
3. PICKIT 2.61 Boot Loader

Necessary Equipment:

1. PIC 16F73
2. LCD 16x2
3. 20 MHz Oscillator
4. Variable resistor (5k Ώ, 1k Ώ, 50k Ώ)
5. 7805 Voltage Regulator
6. 7818 Voltage Regulator
7. LM317T Voltage Regulator
8. LM741 Op Amp
9. Push Button Switch
10. Resistor (1k Ώ, 220Ώ)
11. Capacitor (47, 10, 1, 0.1 uF)
12. Vero board
13. Heat Sink

Methodology:

Figure1: Block Diagram of whole system

Schematic Diagram:

Figure 2: Schematic Diagram of the circuit

Description:

· LM317 can give output of 3-37V . It can change its output voltage according to the adjust pin voltage.
· PWM signal is generated from microcontroller. The signal is applied to RC low pass filter which makes a DC voltage level.
· This voltage is applied to Op Amp to get required gain.
· This amplified voltage is applied to LM317 adjust pin.
· From microcontroller we adjust the width of PWM signal. More width gives higher DC level.
· It also changes the adjust pin voltage which controls the output of LM317.

Final Output:

Possible Application:

· Smooth speed control of DC motor

· Valve control of liquid and gas flow.
· Supply for different Electronic Circuit etc.

Downloads:

Download the full project file here.