Estimating Torque for Solar Panel-Powered Servo Motor

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Discussion Overview

The discussion revolves around estimating the torque required for a servo motor that will rotate a solar panel mounted on a shaft. The context includes considerations of the panel's weight, dimensions, and the operational mechanism of the servo system, which is intended to function as a sun tracker.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the minimum torque rating needed for the servo motor to rotate a solar panel weighing 0.8 kg, plus additional weight from the holder.
  • Another participant suggests that an estimate of the radius of gyration or moment of inertia is necessary, along with a specified rate of angular acceleration.
  • A participant provides additional details about the operational parameters, including the desired rotation of 135 degrees over eight hours and the dimensions of the solar panel.
  • Some participants propose that if the collector is balanced and the angular velocity is small, the required torque from the motor would be minimal.
  • There is a question regarding the sufficiency of a servo with a torque rating of 3.40 kg-cm for the given setup, considering the weight of the panel and the potential need for additional support from bearings at the base.

Areas of Agreement / Disagreement

Participants express differing views on the torque requirements, with some suggesting that the torque needed is small if the system is balanced, while others raise concerns about the weight and structural support, indicating that the discussion remains unresolved.

Contextual Notes

Participants have not reached a consensus on the exact torque requirements, and there are unresolved assumptions regarding the balance of the system and the implications of the panel's weight on the torque needed.

rngd
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Guys, I have a solar panel screwed onto a shaft which connects directly to a servo motor shaft. How much should the torque rating of the servo be to be able to rotate it ? I mean an estimate of the minimum torque required. The panel weighs 0.8kg plus a few grams for the solar panel holder (made of perspex). No gears are used.

Thank you.
 
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You'll need an estimate of either the radius of gyration or the moment of inertia about the rotating axis. You will also have to either assume or specify a rate of angular acceleration about that axis.
 
FredGarvin said:
You'll need an estimate of either the radius of gyration or the moment of inertia about the rotating axis. You will also have to either assume or specify a rate of angular acceleration about that axis.

I would need the servo shaft to rotate a total of 135 degrees, rotating a few degrees every half an hour for eight hours (It will operate like a stepper, stepping during each hour). The speed of rotation is not important, as long as it rotates. The panel's length is 32cm and height is 18 cm. It is a sun tracker.

There will also be another servo to rotate the round base.

Pls see diagram attached below.

Does this help ?
 

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If the collector is balanced, and with the angular velocity being small, the torque required from the motor is tiny. I'd look into a telescope clock drive (if they still make them). Otherwise, you can get a stepper-motor upgrade kit, but they are more expensive than one that just plugs in and runs at the clock rate.
 
russ_watters said:
If the collector is balanced, and with the angular velocity being small, the torque required from the motor is tiny. I'd look into a telescope clock drive (if they still make them). Otherwise, you can get a stepper-motor upgrade kit, but they are more expensive than one that just plugs in and runs at the clock rate.

How tiny ? The panel weighs 0.8kg. Is this servo sufficient (3.40 kg-cm torque) ?

http://www.databitz.com/Resources/crservo.pdf

What about the servo at the bottom (there will be some bearings below the base) ? It seems like the top would be a bit heavy. The whole frame will be made of perspex.
 
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