Table of Important PWM Motor Characteristics

After characterizing a few brushed DC motors from the workshop inventory, the results concluded that a low PWM frequency will improve a motors' low-speed performance and overall speed range. All motors saw a significant reduction of spin threshold voltage when changing the PWM frequency from the MotorKit library's default of 1600Hz to a more compatible 25Hz.

The following charts show each motor's speed, power, and current characteristics as the motor tester swept through PWM Equivalent Voltage values and PWM frequencies. Let's walk through the first, the 1:20 Gearmotor with Encoder, to learn how to read each motor's chart collection. Click on the chart image for an enlarged view.

1:20 Gearmotor with Encoder

The first step in a robotics project is to get a motor spinning. Once you've done that you quickly learn that not all motors go the same speed, even if they are the same part...
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The 1:20 gearmotor combines a high quality motor and gearbox with a quadrature magnetic encoder to measure motor shaft RPM and direction. It's quiet and smooth.

The two charts on the left show the results of sweeping the PWM equivalent voltage from 0 to 5 volts using a PWM frequency of 25Hz and 1600Hz. At the lower PWM frequency, the motor started spinning very slowly at 0.1 volts compared to 1.4 volts at the higher frequency.

The right-hand charts show the motor's response to changing the PWM frequency when the throttle was held at 0.150 (0.75 volts). The first of the two frequency response charts is a closeup of the PWM frequency spectrum from 20Hz to 600Hz; it's a detailed view of the frequency response chart just below it. The motor spins the fastest when the PWM frequency is 20Hz. It drops to 50% of that speed at 142Hz and completely stops spinning when the frequency reaches 508Hz. Note that the motor continues to draw current at frequencies above 508Hz even when not spinning.

1:20 Gearmotor with Encoder, Adafruit PID#4416

130-Size Toy/Hobby Motor

These are standard '130 size' DC hobby motors. They come with a wider operating range than most toy motors: from 4.5 to 9VDC instead of 1.5-4.5V. This range makes them perfect...
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130-Size Toy/Hobby Motor, Adafruit PID#711

RF-300-EH-1D390 CD Spindle Motor

This is a repurposed motor, typical of the smaller round, short-length motors used to spin CD/DVD spindles. The motor's operating range is 2.8 volts to 7.0 volts. The rated voltage of 3.9 volts produces a speed of 4400 RPM.

RF-300EH-1D390 CD Spindle Motor

RF-300FA-12350 CD Spindle Motor

What's this? A record player for ants?? Not at all! This is a DVD/CD Spindle Motor, that thing that's inside a CD or DVD player, that turns the disc...
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RF-300FA-12350 CD Spindle Motor, Adafruit PID#3882

RF-500TB-12560 BoomerPong StringCar Motor

This is a round short-length motor typically used for small fans and CD/DVD drives. The motor's operating range is 6.0 volts to 12.0 volts. The rated voltage of 6.0 volts produces a speed of 2700 RPM.

This is the motor used for the 9-volt series of StringCar racers, including the classic BoomerPong.

Source: Jameco

RF-500TB-12560 StringCar BoomerPong Motor

RF-500TB-18280 String Car M0 Express Motor

This is a round short-length motor typically used for small fans and CD/DVD drives. The motor's specified operating range is 3.0 volts to 6.0 volts. The rated voltage of 6.0 volts produces a speed of 5600 RPM.

The motor will operate reliably with voltages as low as 1.0 volts and is highly efficient at 3.0 volts.

This is the motor used for the LiPo battery powered series of racers, the modern StringCar M0 Express.

RF-500TB-18280 String Car M0 Express Motor

Servo DC Motor

This tiny DC Motor in Micro Servo Body is an interesting motor - it's the same size and shape as our micro servo but it isn't a servo. It's...
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Servo-Sized DC Gearmotor, Adafruit PID#2941

Blue TT Motor

These durable (but affordable!) gearbox motors (also known as 'TT' motors) are an easy, low-cost way to get your projects moving. This is a TT DC Bi-Metal Gearbox...
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Blue_TT Gearmotor, Adafruit PID#3801

Yellow TT Motor

Perhaps you've been assembling a new robot friend, adding a computer for a brain and other fun personality touches. Now the time has come to let it leave the nest and fly on...
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Yellow_TT Gearmotor, Adafruit PID#3777

Uxcell-ux0188 Motor

This is a round long-length motor typically used for RC vehicles. The motor's operating range is 3.0 volts to 9.0 volts. The rated voltage of 6.0 volts produces a speed of 6300 RPM.

This is the noisiest and most unpredictable motor in the workshop's collection. It found a home in an audio-powered laser galvanometer project. Besides chattering bearings, the motor's internal windings vibrated as loudly as a small loudspeaker.

Uxcell-ux0188 Motor

This guide was first published on Feb 23, 2021. It was last updated on 2021-02-23 15:22:04 -0500.

This page (Motor Performance Charts) was last updated on Apr 22, 2021.

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