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Arduino - controlling high voltage device using transistors

Arduino - controlling high voltage device using transistors

Arduinos and raspberry pi's operate at a lower voltage (5v) and controlling led's, servos etc can be done this voltage or with a simple transistor based switching. In this post i will show different techniques used to control devices at a higher voltage and power levels. These techniques can be used in conjunction with many other projects for e.g remote controllers  to control high power devices like room heaters, lamps e.t.c In general, you need to couple the 5voltage control signals to the input of these switching circuits.

Controlling DC motors at 12 volt with Speed controle (PWM)

Controlling DC motors with PWM (pulse width modulation, to control the intensity/speed) is straight forward. Here we use a special transistor (TIP-122, datasheet) which is a darlington pair and can switch a device up to 100Volts (DC). It is a TO-220 package with all inside the package (see figure). Connect the PWM output (for speed control) to the base of TIP-122. Connect emitter pin to ground and collector pin to C fan/motor and the other end of fan to positive end of 12v DC.

Use any pwm pin (eg Pin 9 with analogWrite(9,speed_value);) and connect it to the base of the transistor (TIP-122) via 1k resistor

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