DC motor options

Discussion in 'The Projects Forum' started by willy_d, Aug 6, 2010.

  1. willy_d

    Thread Starter New Member

    Aug 6, 2010

    I am wanting to measure the torque produced by motor under a dynamic. The only constraints i have is that the power supply is DC, the motor needs to be able to supply around 1Nm of torque and i want to keep a reasonably constant speed of around 80-100 rpm...

    I am current using a simple brushed dc 12v Drill motor fitted with a speed control. i am measuring the current and voltage and by calibration i have found a relationship between power and torque..

    i have been told that a brush less DC could be better option as the speed can be controlled more accurately and torque computed more easily??

    Or has anyone seen motor packages with a load cells fitted to the stators so that torque can be directly measured???

    i am pretty new to all this sort of stuff so any help will be appreciated.. even if you could just point me towards some good shops or websites to check out.

    i am purely looking for the simplest and most robust solution, cost is not too much of an issue.

    Thanks, willy
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    I am confused. By power, I assume you mean the input power. How did you measure the torque?

    How big a motor are you talking about? At what speeds will you be operating? Can you put something like a propeller on the motor shaft for a load?

  3. willy_d

    Thread Starter New Member

    Aug 6, 2010
    thanks for the reply John

    Yip, by power i meant the power input. I have done a de prony brakes test to find relationship between input power the torque output, characteristic of the motor.

    I am then monitoring the current/voltage input when the motor is in use and sending it to my laptop where i then convert the current/voltage to a power, then finally using the relationship found i am converting it to a torque.

    This method works alright but i wanting more accuracy. once the battery becomes a little depleted my speed drops and causes more error. I am told that brush less DC motors are far better for speed control and current voltage can be monitored more easily.

    I have also been told about motors that come with strain gauges or load cells fitted where the motor mounts to its housing so that torque can be directly measured. Although I have not been able to find info on these yet.

    i am looking to make torque reading i'm getting as robust and reliable as possible ie little dependence on battery level and temperature of components.

    thanks again, willy