Rc speed controller

  • I have a berdair pump and have been debating on using a spare brushless quad copter motor and speed controller. Would the duet be able to controll said controller?

  • Sure others will reply with detail but essentially you are sending a servo control signal to the speed controller and many have used servos in their printers. Think they use a spare hot end heater output for the pwm signal. The speed controller should act as a nice protector from any of the inductive nastyness you would get with direct drive too. Have a look for how the CNC lot control the speed to the spindle. I could see speed controllers being needed there too.

  • @bendiesel
    ESC's for RC use have safety features built in that prevent them from being easily used for PWM input for example. When you power up an ESC, the motor is disabled so that a prop doesn't chop you up the second you connect a battery. You can buy cheap BLDC drivers via ebay that handle far more power than you'll ever need and have PWM input. Tese devices don't have the ESC-type safety features. I have used this type to run CPAP blowers for remote print cooling.

  • Interesting.
    My understanding was that the remote transmitter the "arm" feature.

  • @bendiesel said in Rc speed controller:

    My understanding was that the remote transmitter the "arm" feature.


    The transmitter just sends something (many different ways) that ultimately becomes a PWM signal. 1.0 millisecond pulse width is "off", 2.0m is "full on", and intermediate things like 1.5ms would be half throttle.

    Arming is a matter of the ESC seeing 1.0 ms (or less) for a second or two. If, when the ESC powers up, it is receiving no pulses (because the ESC booted faster than the RX 'linked'), that's fine. However, if the first pulses it sees are, say 1.4ms, then the idiot human did not zero the throttle on the transmitter before powering everything up. The ESC will just not do anything until it sees 1.0 for a while, then it will beep (actually, use the motor coils for a speaker). AFTER that, if it sees the pulses go up, it will spin the motor, etc.

    Short version: The TX just sends a position. The ESC arms when it sees that position at or near zero for a while.


    Having said all of that, there are two or more slight caveats:

    First, 1.0 to 2.0 is a pseudo-standard, and some RC radio systems will really be .9 to 2.1 or 1.1 to 1.9 or whatever. Sometimes, the ESC will 'self calibrate' to all of this. Sometimes, the ESC has an explicit sequence it wants to see to 'memorize' the endpoints. Sometimes, the human has to adjust the endpoints in the transmitter (generally the low endpoint, even lower) to get the ESC to arm.

    Second, remembering that this standard was originally for SERVOS, back there were no hobby ESCs, in their infinite wisdom a few manufacturers decided that 2.0 was "all the way left" and a few that 2.0 was "all the way right". When ESCs came out, there really was no standard about 1.0 being "min" and 2.0 being "max"... and... very few ESCs had the concept of 'arming'. Early electric ESC/Motor/Prop were infamous for starting at full power, when used with certain brands of TX. Arming helped solve this.

    So, a long time ago, and to some extent still today, if an ESC flatly won't arm, step 1 is reverse the throttle channel on the TX. Step 2 is lower the 'bottom' endpoint. Step 3 is read the book or call an expert. 🙂


    Anyway, this all ties back to using a hobby ESC with servo output on a 3D Printer (or CNC) controller that it going to use G-Code to make outputs happen, in PWM form, to that ESC. A hobby ESC is quite likely to require a "Start Script" with the appropriate G-Code to output "all the way min" (really 1.0ms pulse) and delay for several seconds.

  • Last time I used much in the RC world it was racing model cars when it was still 27mhz and brushed DC motors! 😄

    Thinking on it that was about 22 years ago! Did have a car project with 4 mini bldc motors but it got shelved when a full sized car project came along. I'll remember your comments though as that would have caught me out!

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