How to Limit the Top Speed of a Stepper Motor

Stepper motors are awesome for their precise movements, but sometimes you just need them to slow down.

Here’s a quick look at some of the methods you can use to limit the top speed of your stepper motor:

1. Pulse Width Modulation (PWM)
2. Current Limiting
3. Microstepping

#1 Pulse Width Modulation (PWM)

PWM doesn’t give the motor full power all the time. Instead, it turns the power on and off very fast, making pulses. The longer the pulse stays on, the faster the motor spins. It’s like making a light brighter or dimmer by flicking the switch fast – the longer it’s on, the brighter it gets.

1. Fast Timer: There’s a timer that counts really fast, like 100 times every second.
2. Pulse Length: This timer decides how long each pulse lasts.
3. Duty Cycle Control: You control the ‘duty cycle,’ which is how much of the time the pulse is on. It’s like a percentage.
4. Speed and Duty Cycle: If the duty cycle is high, the motor gets more ‘on’ time. It’s like a light being on more, so the motor goes faster.
5. Slowing Down: If the duty cycle is low, there’s less ‘on’ time. It’s like the light being dimmer, so the motor goes slower.

#2 Current Limiting

Current limiting in stepper motors is like controlling the flow of fuel to a car’s engine. In a car, less fuel means the engine runs slower. In a stepper motor, the current is the fuel. When you limit the current, the motor slows down.

Ways to Limit Current:

1. Using a Driver:
   • Most stepper motors use a driver, which controls the motor.
   • These drivers usually have a way to limit current. It’s like a knob or a setting.
   • By adjusting this, you decide the maximum current the motor can use.
   • This is like controlling how fast water flows through the hose.
2. Using a Resistor:
   • You can also add a resistor to the motor.
   • A resistor limits how much current can flow through the motor.
   • The bigger the resistor, the less current flows, and the slower the motor turns.
   • It’s like using a smaller hose to slow down the water flow.

Current limiting is a good way to control your stepper motor’s speed. It’s useful when you need the motor to move at a certain speed, like in 3D printers or CNC machines. By controlling the current, you control how fast or slow the motor turns. This method is simple but very effective for precise speed control in different applications.

#3 Microstepping

Microstepping in a stepper motor is like adding small steps between the big steps. It gives you more control over how the motor moves and how fast it goes.

How Microstepping Works:

1. Dividing Steps:
   • Your motor’s normal steps are split into smaller parts.
2. Motor Controller Role:
   • The motor controller activates different parts of the motor to make these small movements.
3. Controlling Speed:
   • By changing the number of microsteps, you can adjust the motor’s speed very precisely.

Benefits of Microstepping:

1. Smoother Movement:
   • It reduces shaking and noise when the motor moves slowly.
2. Increased Precision:
   • It allows the motor to be placed very accurately.
3. More Power at Low Speeds:
   • Microstepping can give the motor more strength at slower speeds compared to normal stepping.

Microstepping is useful for jobs that need careful and smooth movements. This includes things like robots, 3D printers, and machines that cut or shape materials (CNC machines). It helps these devices work better and more accurately.