Motor speed controller with timer 555

Posted on Jul 7, 2012

Pulse width modulation (PWM) is a technique to control analog circuits with a digital output. PWM is used in many applications, Specially to control light intensity and speed on motors. A PWM circuit makes a square wave with a variable width. The pulse width in this circuit can be varied from 5% to 95%. Used in a dimmer, this circuit controls the light intensity according the pulse width. On speed controller, the power of the motor depends the width from 5% (low power/speed) to 95% (full power/speed). The main disadvantage of this circuit, as all PWM circuits, is the possibility of generating radio frequency interference (RFI). It can be reduced changing the capacitor.

Motor speed controller with timer 555
Click here to download the full size of the above Circuit.

Parts needed: * 1 1k Resistor * 1 1mF Capacitor (Tantalium capacitors works great) * 2 4148 Diodes * 1 100k Variable resistor * 1 IC 555 oscillator. Germanium diodes can be used to increase the range of the PMW up to 1% to 99%.

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