I’m building a robot using Pololu micro metal gearmotors, and I’ve noticed that the torque is very low using PWM (I’m using the Dagu Mini Driver). If I try running one of the motors directly off a battery pack with the same voltage as the PWM is generating, the torque is much higher. Is this normal? Thanks for your help–I’m very new to all this.
Your newness is showing.
You really haven’t provided enough information for anyone to seriously help you. Voltage being provided to the motors would be a good start and at what PWM you are noticing your issues. I am sure there is more relevant information you could offer, but, my mind is not offering the answers to me at this time.
Motor Drivers
There is a voltage drop across the motor driver chip. Also make sure the PWM is on full for comparsion purposes. Do you have the tools to measure?
It’s normal to have a lower
It’s normal to have a lower performance with a motor driver that directly from the battery, but usually they have 90% efficiency. Try with 255 as pwm value, which is the max speed. Be sure to connect dagu mini driver to the battery and switch it to battery powered, the current from usb is too low.
The timer settings that
The timer settings that effect PWM can be a cause of loss of torque. OddBot has a posting or two about the ideal settings for small motors. I’m not sure what the ideal setting are, but I recall around 100Hz or so.
EDIT: the article is at https://www.robotshop.com/letsmakerobots/changing-pwm-frequencies-arduino-controllers
Okay…
Thanks for the comments so far. When I have a chance I’ll try 255 and see how the torque feels then. I don’t have the code in front of me to check the current setting, but I’m measuring 6V on the motor pins, and I was hoping not to have to run them much faster. I’m using a 6-cell NiMH pack.
OddBot, what the default PWM frequency setting on the Mini Driver, and can this be changed?
Okay, got it. Thanks again
Okay, got it. Thanks again for helping out a newbie!
Question regarding PWM, frequency and torque
Can I use the 490.2Hz PWM pins on my Spider controller or do I
have to change the frequency somehow?
Also: may a PWM value lower than 30 damage the motors? My Dagu Rover 5 only
makes humming noise with PWM values below 30 (and yes I limit the PWM at 200
max).