Universal motor speed control by a microcontroller (arduino)

TL;DR

Learn how to control the speed of a drill motor using an Arduino and a simple circuit involving a triac, variable resistor, capacitor, CDS photo resistor, and LED.

Transcript

okay in this video I'm going to talk about uh speed controlling a drill motor with an Arduino uh I originally started this and thought the best way to do it would be to rectify the AC into plain DC and then use an optoisolator and raw pwm just to chop up that DC and send it to the motor uh but this turned out not to work very well because uh my cir... Read More

Key Insights

• 🥺 Controlling the speed of a drill motor using rectified AC and optoisolator with raw PWM can be unreliable and lead to circuit failures.
• 😵 Using a triac and opto triac for controlling AC voltage with an Arduino requires a zero cross detector and programming with interrupts, adding complexity to the project.
• 🧑‍🦼 Hardwiring the trigger switch of the drill motor and using a circuit board with a triac, variable resistor, and capacitor can provide a simpler solution for speed control.
• 😴 The speaker's solution involves replacing the potentiometer with a CDS photo resistor and an LED, controlled directly by Arduino through a PWM pin.
• 😘 This alternative solution eliminates the need for complex programming and additional components, resulting in a low-component solution.
• 🧑‍🦼 The speed of the drill motor can be finely controlled by varying the brightness of the LED through PWM signal.
• 🙂 The circuit can be protected from room lights by using tape or designing a light-tight case in the future.

Questions & Answers

Q: What were the challenges faced when trying to control the drill motor using rectified AC and optoisolator with raw PWM?

The circuit was not robust, leading to frequent failures, blowing out mosfets and protection diodes. The high power and design of the drill motor posed difficulties in this approach.

Q: How do people typically control the drill motor with Arduino using a triac?

By using a triac and opto triac controlled by Arduino, a person can control AC voltage. However, a zero cross detector and two optocouplers are needed for timing, making the programming complex.

Q: What is the alternative solution proposed by the speaker?

The speaker replaced the physical potentiometer with a CDS photo resistor and LED controlled directly by Arduino through a PWM pin. This eliminates the need for a zero cross detector and reduces complexity.

Q: What additional components are required for the alternative solution?

The additional components required are a triac dimmer circuit (which can also be a standard dimmer for house lighting), a CDS cell, and an LED.

Summary & Key Takeaways

• Initially tried rectifying AC into DC and using an optoisolator and raw PWM to control the drill motor speed, but encountered circuit failures.

• Explored using a triac and opto triac controlled by Arduino, but this required a zero cross detector and programming with interrupts, which increased complexity.

• Found a simpler solution by hardwiring the trigger switch of the drill motor and using a circuit board with a triac, variable resistor, and capacitor for speed control.