Tsukure Mad Labs DC Motor Speed Controller

The DC Motor Speed Controller circuit is primarily a 555 IC based PWM (Pulse Width Modulation) circuit developed to get variable voltage over constant voltage.

When power is supplied, 555 TIMER generates PWM signal with a duty ratio based on the pot resistance ratio. Because of the pot and the diode pair, here the capacitor (which triggers the output) must charge and discharge through a different set of resistance and because of this, the capacitor takes a different time to charge and discharge. Since the output will be high when the capacitor is charging and is low when the capacitor is discharging, we get a difference in high output and low output times, and so the PWM.

This PWM of timer is fed to the signal pin of L239D h-bridge to drive the DC motor. With the varying PWM ratio we get varying RMS terminal voltage and so the speed. To change the direction of rotation the PWM of timer is connected to the second signal pin.                                  

Components used in this module...

Find out more about the components used in this STEM Module.

Let's Get Started!

Below you will find a list of bits to gather before hand, followed by a detailed schematic. Using a breadboard lay out the components and connect them together as shown. Alternatively you can purchase this module from our shop and simply solder the components in the places indicated on the quality assured printed circuit boards provided.

What You Need...

1 103 (10nF / 0.01uF) Capacitor (Ceramic)
2 1N4148 Diode
1 555 Timer Integrated Circuit (IC)
1 L293D Stepper Motor Driver Integrated Circuit (IC)
1 9V DC Motor Motor
1 100R
[ Brown, Black, Black, Black ]
Resistor (0.25 Watt)
1 1K
[ Brown, Black, Black, Brown ]
Resistor (0.25 Watt)
1 100K Resistor (Potentiometer / Variable)

NB: Any resistor colour codes specified relate to 5 band resistor codes, the 5th band has not been shown intentionally. The 5th band indicates the resistor tolerence, we use only the highest tolerence resistors in our products.

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