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I'm using a Raspberry Pi, a PCA9685 controller, and a servo to control the air intake lever on my woodstove based on stove and room temperatures. My code adjusts the servo position every 2 minutes and there is no force from the stove lever on the servo except when it's moving to a new position (and the servos were perfectly quiet when idle). The system runs 24/7 and is working great. Except that now two servos have burned out - the first lasted 6 weeks and the 2nd one only 4 (seems the internal electrics failed, all the gears are fine). Are servos designed to be "on" 24/7 for months at a time? If not, is there a way to turn the servo off via the PCA9685 controller to lengthen its lifespan?

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Answer

There are a couple of things to prolong servo life:

(1) Using a switching regulator with a small current limit, say, less than 5009mA, then when the servo is over loaed, get stuck etc. stall current will be small, and therefore not heating up the motor and fry it.

(2) Use Rpi or PCA9685 GPIO pin to switch off eg, the LM2596 switching power supply to save working or idle current.

(3) Do not buy fake servos from eBay. Instead, buy from authorized distributors.

(4) Move servo in small steps for a smooth travel, therefore reduce abrupt movements causing unnecessarily large current and wear and tear by friction and heat.

(5) Regularly lubricate the stove damper lever to reduce friction and therefore lighten servo work load.

(6) Replace the dc motor and potentiometer (need DIY skill, but they are sort of standard parts, therefore easy job for hobbyists) with good quality ones, before or after burning out, to prolong servo life.


Problem Analysis

1. The following wood stove is used as a case study and example for reference.

Wood Stove and stove Lever

I am assuming the OP's wood stove and the stove lever is similar to the picture below.

wood stove


2. TowerPro MG995 and SG spec are used as references

sg90 and ms995 servo


3. MG995 Spec is used to design speed and current for the wood stove servo

mg995


I am assuming genuine servos are used.

fake mg995


References


Appendices


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