This is a variable power supply controlled with PIC microcontroller. There is LCD display in this circuit which will show the actual value of power supply output. This power supply use push on switch to adjust the output voltage and current value.

Schematic Diagram:

Component List:
C1 = 2000uF per AMP, 40V (adjust capacity to power supply amps)
C2,C3,C12,C15,C18,C21 = 0.1uF CER
C4 = 0.01uF CER
C5A,C5B,C5C,C5D = 0.01uF CER
C6,C7 = 0.05uF CER
C8 = Not used
C9,C11,C19,C20 = 1uF CER
C10 = 470uF 15V EL RADIAL
C13 = 4.7µF 50V EL RADIAL
C14 = 0.001uF CER
C16,C17 = 22pF CER

This battery charger circuit is used for rechargable lithium battery.

Charging is accomplished with a constant current of 60 mA for AA cells to a cutoff of 2.4V per cell, at which point the charge must be terminated.

This low power inverter uses only 9 parts and turns 10 to 16VDC into 115V / 60Hz square wave power to operate AC equipment up to 25W.

The first section of the 555 timer is wires as an astable oscillator with R2 and C1 setting the frequency. The output is available at pin 5. The second section is wired as a phase inverter. That output is available at pin 9. Resistor R3 and R4 keep output transistor Q1 and Q2 from loading down the oscillator.

This is an adjustable power supply which have adjustabled output voltage from 6-12 DC volt.

Component Parts List:
T1 = 115[220]/8 VAC transformer. Center Tap not needed.
Q1 = 2N1613, NTE128, or substitute. (TO-39 case) On coolrib!
BR1 = 40V, 4A. (Check max current of your mini-drill and add 2A)
R1 = 470 ohm, 5%
R2 = 1K, 5%
P1 = potentiometer, 10K
C1 = 1000uF, 25V

This is a 12VDC to 9VDC Converter circuit. You may use this circuit if you have fixed 12V power supply / battery, but you need 9V power supply for your electronic devices.

Component Part List:

R1________ 560 ohm
C1________ 1000μF/16V, Electrolytic
C2________ 100μF/16V, Electrolytic
C3________ 330nF, Ceramic
Z1________ 9.1V, 0.4watt zener
Q1________ ECG184, NTE184