FAQ - PWM

Frequently Asked Questions about Apollo Controllers and PWM

 

Do the Apollo Controllers use PWM?

Yes.

Is PWM bad?

No. Absolutely not. 

What is PWM, and why does Apollo use it?

Pulse Width Modulation (PWM) is a modern, efficient method of delivering precise voltage control to motors. Apollo uses high-frequency PWM to provide smooth, consistent control with excellent torque and low heat—ideal for model railway operation.

How common is PWM?

Pulse Width Modulation (PWM) is widely used in electronics and control systems where precise, efficient control of power is needed. Common applications include controlling motor speed in robotics and appliances, dimming LEDs in lighting systems, generating audio tones or signals in embedded systems, and regulating voltage in power supplies and DC-DC converters. Many everyday appliances use PWM to control motor speed efficiently and quietly. Examples include:

DVD Players use PWM to control the motor that spins the discs with absolute precision. 

Power Windows in cars use PWM. 

Ceiling fans often use PWM to vary motor speed without the hum or heat of traditional resistive control.

Blenders and food processors use PWM to offer variable speed settings while maintaining torque.

Washing machines (especially front loaders) use PWM to control drum rotation smoothly during wash and spin cycles.

Cordless power tools use PWM via their electronic speed triggers to regulate motor output depending on how far the trigger is pressed.

Electric toothbrushes and shavers also use PWM to maintain consistent motor speed even as battery voltage drops.

I heard PWM can damage model railroad motors. Is that true?

Some controllers in the 1970s and 1980s used high-voltage spikes on the rails to drive the motors. These controllers were notorious for burning out motors. They called themselves "PWM" but they were not actually true PWM - not even close. Proper PWM uses a clean square-wave signal at the same normal voltage that any other controller would use. 

Apollo controllers use well-filtered, high-frequency PWM that is safe for modern and vintage motors alike, including coreless and can types.

Is PWM bad for older motors or open-frame types?

No. Apollo’s PWM is gentle and compatible with most traditional motors, including open-frame and Triang-style designs. In fact, PWM often gives better low-speed control and improved efficiency compared to older variable-voltage systems.

Is PWM currently used in model railroad applications?

Yes. Every DCC module uses PWM. Let me say that again, EVERY single DCC module uses PWM. If your locomotive is "DCC-ready" or "DCC-compatible" it will handle PWM just fine. 

Aren’t traditional DC controllers safer or better?

Traditional linear DC controllers waste power as heat and offer less torque at low speed. PWM gives superior performance with less stress on motors, and Apollo’s design ensures clean, reliable operation with modern protection features built in.

If PWM is so good, why do some say it’s bad for certain motors?

Ironically, the same manufacturers warning against PWM say their products are DCC compatible, which themselves use PWM internally to drive the motor. In fact, all modern DCC motor control is based on PWM—often at similar or even higher frequencies than Apollo controllers. If your locomotive can be fitted with a DCC decoder, then it is already designed to handle PWM safely. Apollo simply delivers PWM from the track rather than through a decoder, giving you many of the same performance benefits without the cost or complexity of DCC.

So manufacturers that warn against PWM don't really know what they're talking about?

You got it!