5 5V UPS Circuit

This UPS has a regulated and uninterrupted 5V output. This type of UPS is very useful to low power 5V devices, microcontrollers, and some memory modules. This UPS design has a very stable 5V output but the drawback is very low efficiency. 

5V UPS schematic

Part List:
R1 - 39 ohms 1/2W
D1, D3, D4 - 1N4001 or similar diode
D2 - 13V zener rated 1W
C1 - 220uF electrolytic capacitor rated 25V
C2 - 10uF electrolytic capacitor rated 10V
IC - 7805 or similar 5V regulator
BAT - 12V lead acid battery rated 1.2Ah minimum
DC INPUT - see AC-DC converter below

AC-DC converter

Part List:
D - 1N4001 or similar dioded
C - 2200uF electrolytic capacitor rated 25V
Transformer - Primary (220V or 110V), Secondary (12V-0V-12V) rated 12VA minimum

Similar UPS circuits:
6V UPS
Simple 12V UPS

4 6V Uninterruptible Power Supply (UPS) Circuit

This is a simple 6V UPS circuit that you can use to device that plays a critical function and needs not be interrupted .This UPS is much cheaper compared to the 12V version since it uses only transistor and no IC.

UPS schematic

Part List:
R1, R3 - 560 ohms 1/4W
R2 - 1 kilo ohms 1/4W
D1 - 1N4736A or any 6.8V zener diode
D2 - 1N4001 or similar diode
LED - red LED or any low power LED ( see Led info to know more)
C1 - 47uF electrolytic capacitor rated 16V
Q1 - 2N3440 or similar NPN transistor
BAT - 6V battery (Lead Acid or chargeable)
DC IN - see AC-DC converter below

2N3440 pinout

DC IN:

AC-DC converter schematic

Part List:
Transformer - Primary (220V or 110V)' Secondary (9V-0V-9V) rated 10VA
D - 1N4001 or similar rectifier diode
C - 470uF electrolytic capacitor rated 16V

1 Power Supply with Selectable Output

This simple power supply unit (PSU) uses LM317 IC and can deliver 1.5A current with selectable voltages. Outputs are 1.5V, 3V, 4.5V, 6V, 9V and 12V. The output voltage is controlled only by the resistor combinations. You can use the LM317 calculator to determine these resistor values.

PSU schematic diagram

317 pinout

Part List:
C1 - 2200uF electrolytic capacitor rated 25V
C2, C5 - 100nF Mylar or ceramic capacitor
C3, C5 - 22uF electrolytic capacitor rated 16V
R1, R2, R7 - 120 ohms 1/4W
R3, R4 - 240 ohms 1/4W
R5 - 100 ohms 1/4W
R6 - 20 ohms 1/4W
D1, D2 - 1N4004, 1N4007 or similar silicon diode
317 -  LM317 or similar regulator IC
S1 - rotary switch
DC - see AC to DC converter circuit below

Part List:
Transformer - 220 to 12V center tap rated 15VA minimum
D - Any rectifier diode rated 2A minimum
C - You can omit since we got C1 (2200uF)

Note: I recommend using 220V/15V center tap but excessive heating might occur on when 1.5V is selected and with 1.5A output. The lower the output voltage with higher current, the higher the tendency the LM317 will overheat.

0 Switchable DC Power Supply

This is a simple way of converting your standard DC source in a switchable power supply unit. Shown below is a simple circuit using a discrete regulator out from a transistor and zener diode combination. The circuit can deliver a maximum current of 1A (higher current if modified) at an output of 3v, 6V, 9V, and 12V.

Regulator schematic

Part List:
R - 56 ohms 5W (3W is the minimum)
Q - TIP41C, 2N3055 or similar NPN transistor
D1 - 1N4728A, or 3.3V zener diode rated 1W
D2, D3, D4 - 1N5225B, or 3V zener diode rated 0.5W minimum
Fuse - 1A fuse
DC input - 14V to 18V DC source

2N3055 pins

TIP41C pins

Note:Transistor must have a heatsink. You can add capacitors across the input and output terminals for better regulation and clean DC output.

1 +12V and -12V power supply

This power supply is useful in powering opamps, comparators, and small amplifiers that uses dual input voltage source specially  +12V, ground (0V), and -12V voltages.The circuit is based on the two complementary voltage regulators the 7812 (+12V) and 7912 (-12V). In building the circuit, check the polarity of the electrolytic capacitor to avoid problems.

dual 12V power supply

Materials:

1 - Transformer is 220VAC to 15V -0 -15V, 2A   or  (120V to 15V -0 -15V, 2A)
1 - bridge rectifier diode  rated 2A 
2 - 2200uF 25V electrolytic capacitor
2 - 220uF 16V electrolytic capacitor
1 - 7812 or any +12V regulator IC
1 - 7912 or any -12V regulator IC


Note: This power supply project is powered through  main supply and can cause electrocution.