Circuit Project Electronic

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Here is circuit 9V power supply regulator with battery 12V backup system.
Use IC 7812 and 7805 control voltage output by R3 1K output 9V 1A max.
This is a 9V power supply which will work even on power failure. It uses a rechargeable battery and regulators. A transformer with 15-0-15 [...]

This power supply is not designed to use the prefabricated IC voltage regulators, even though such regulators do exist. The 7812 and 7912 ICs are quite capable of providing regulated +12 volt and -12 volt outputs, respectively. However, we have two problems with doing it this way. First, each regulator provides an output voltage accurate [...]

Three LEDs signal bumper-barrier distance
Infra-red operation, indoor use
Parts:
R1_____________10K 1/4W Resistor
R2,R5,R6,R9_____1K 1/4W Resistors
R3_____________33R 1/4W Resistor
R4,R11__________1M 1/4W Resistors
R7______________4K7 1/4W Resistor
R8______________1K5 1/4W Resistor
R10,R12-R14_____1K 1/4W Resistors
C1,C4___________1µF 63V Electrolytic or Polyester Capacitors
C2_____________47pF 63V Ceramic Capacitor
C3,C5_________100µF 25V Electrolytic Capacitors
D1_____________Infra-red LED
D2_____________Infra-red Photo Diode (see Notes)
D3,D4________1N4148 75V [...]