How to make your own power supply unit
for all your electronics and embedded system experiments. It also has a backup
battery which will be used in case of power cuts and a display.
Components Required
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
7. GPCBs
8. Step-down Transformer
16-18V/3 Amps
9. 1N4007 Diodes x 4
10. Two Relay Module
11. Capacitors
12. Resistors
13. ATmega16/8 Development board
14. 16x2 LCD
15. Heat Sinks
16. Enclosure
Features:
- 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.
Block
Diagram
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.
Charge Indicator: This is nothing but two
resistors arranged in from of a voltage divider circuit. It scales down the
voltage level of battery for the microcontroller to read it.
Relay 1: This is a relay module which
switches between the charge indicator circuit and charger circuit depending on
the command from microcontroller.
The battery’s +ve terminal is connected to the
common pin. The charging circuit is connected to the Normally Open pin and
charge indicating circuit is connected to the Normally Closed pin.
When the mains supply is in OFF state, the relay
disconnects the charger from battery and connects it to the indicator so that
the microcontroller can read the battery level and display on the LCD. When the
supply is ON, the indicator circuit is disconnected and the charging circuit is
connected to the battery.
Relay 2: This relay module switches
between mains supply and battery supply depending on the command from
microcontroller.
The battery’s +ve terminal is connected to the
Normally OPEN pin and +ve line from main power supply block is connected to the
Normally CLOSE pin. The common pin of relay is connected to the DC PSU block.
When the mains are unavailable, the
controller automatically switches the relay to battery mode.
Note: The +12V for
powering the relay is given directly from the battery. This allows the relay to
purely function based on the command from microcontroller instead of
availability of power.
DC PSU: This block consists of the voltage
regulators and a bunch of capacitors. +5V, +9V and adjustable voltage levels
are provided by the ICs 7805, 7809 and LM317 respectively.
The +5V line is also connected to the microcontroller
board and LCD.
Note: The +12V for
powering the relay is given directly from the battery. This allows the relay to
purely function based on the command from microcontroller instead of
availability of power.
DC PSU: This block consists of the voltage
regulators and a bunch of capacitors. +5V, +9V and adjustable voltage levels
are provided by the ICs 7805, 7809 and LM317 respectively.
The +5V line is also connected to the
microcontroller board and LCD.
Panel Display: This is the front and outer
panel block which consists of the main switch, LCD displaying the voltage
level, Potentiometer Knob to adjust the voltage, Banana connectors and screw
terminals.
This is how I want it to look like:
The icons on
the LCD indicate the following:
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2 comments
Write commentsWe do not see them often and when we do, we have a hard time recognizing them. However, most of us must have used a single board computer in one form or another.
Replyembedded board
What does enabling 'remote automation' in the advanced settings do? click here to get more.
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