This is a simple charger circuit for charge single cell 3.7V lipo battery. The heart of the charger is TL431 shunt regulator that controls the incoming current. Charger comes with a convenient charging LED indicator. As charging current goes down so does the intensity of the LED.source

This is a solar power center, it can be used to handle all of the power functions for small 12 Volt solar powered devices. It contains a photovoltaic charge controller and a low voltage load disconnect circuit. The low voltage disconnect has a load on-off switch, and a battery low voltage indicator. source

You can add this high-efficiency dimming and flashing circuit to an existing battery-powered lantern or flashlight or to a custom design. For the car it makes a great lamp for changing a flat tire, back seat reading or emergency engine work. The flasher mode is useful for warning other drivers of your troubles and it [...]

This is DC motor speed control based on PIC16F867.The circuits use frequency PWM about 10KHz which does not make a noise in the motor.This project can drive 1 Amp motor current without over heat.The motor speed controled by potentiometer which is connected to ADC input pin.source

Ultra-Linear operation provides a compromise between the high efficiency of tetrodes and the low distortion and uncritical load impedance of triodes.There is an undoubted advantage in modulator service because the matching of the modulator to the RF stage is not so critical and the screen (DC) supply is obtained “automatically” from the transformer.source