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Servo Torque Question — Parallax Forums

Servo Torque Question

PlusOn3PlusOn3 Posts: 15
edited 2012-01-20 15:42 in Robotics
After looking up data about servos I might use for a project I am working on I notice that they all seem to have a range of voltages that they would work at. And they also seem to correlate the amount of voltage being applied to how much torque is maintained. The project I am trying to start would require the use of at least 8 or so servos (not 100% sure how many exactly yet). I would be using the propeller servo controller usb (http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/28830-PropServoControllerUSB-v1.0.pdf) to control the servos. So if I plugged in 7.5V to the propeller servo controller usb, and the maximum voltage for the servos I plug in in 7.5 volts, would they all be operating at the maximum torque or would it be reduced because I using that 7.5 volts to cover multiple servos? Also, if the maximum voltage for the servos was only 5.5V and I plugged in 7.5V to the propeller servo controller would that damage the servos even if I had multiple servos plugged in (I'm pretty sure the answer is 'yes it would', but I just want to make sure.)

I hope I explained that well enough. If not, please let me know and I can try to reword and explain more.

Thanks!

EDIT: Also is there any circumstance to which I should use any other type of battery than just standard batteries, like duracell or something like that. (Ni-Cd, Ni-MH, LI-Ion)?

Comments

  • Martin_HMartin_H Posts: 4,051
    edited 2012-01-20 15:38
    All the servos are in parallel, so they all experience the same voltage drop. But the current from the power supply divides among them. So the torque they produce is a function of voltage and adequate current for the motors. The propeller servo controller spaces the servo control signals out in time, so they don't all draw peak current at the same time. So you have a bit more headroom than if you were running a bunch of dc motors.

    I would avoid over voltage of the servos as it will likely decrease their life. But I've done it and my servos survived.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-01-20 15:40
    For heavy duty use you could connect the power and ground of all the servos to a separate power source using appropriately sized wire. Only the signal wire and ground need to go to the servo controller.

    For high current draw use NiMH or LiPo.
  • PlusOn3PlusOn3 Posts: 15
    edited 2012-01-20 15:42
    Wonderful! Excellent advice as always from these forums!! Thanks so much to everyone that provides help to those of us that don't know too much. Maybe one day I will know enough to pay it forward to other beginners!
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