Powered up Static Servo Service Life Query

[BrendanP]

I have been off the forum for a while. Greetings to all my friends here.

I have two Hitec HS311 RC servos acting in a pan/tilt app. The control move a small circular pcb (110 mm diameter tightly loaded with smd) with a 3G camera, module etc on it.

I see the servos in effect "lock up" when the pcb (and consequently the servos) is powered up. When the power is removed the servos can free wheel. Obviously they are designed like this to holds control surfaces on RC aircraft rigid whilst in flight.

In my app the servos will be continuously powered up for months on end. I cannot detect any heat emanating from them on the test bench. What sort of life span could I expect to get from them in this role? Do the internal motors wear (over heat) even though they are not moving? I thought the windings insulation might break down etc.

Any advice will be appreciated.

 

[srnet]

A servo at rest consumes very little current, but consumes a lot more current when its moving.

Use a multimeter to check the current draw of the servo ?

 

[boriz]

Some servos will be better than others in this respect. The crucial thing though, is to make sure your load is mechanically balanced so there is no net torque on the servo shaft when at rest.

 

[BeanieBots]

Windings and insulation will be of no concern at all.
What you need to worry about is brushes and gears.
As boriz points out, a lot depends on the servo itself and the static load. Obviously, brushless servos won't have any issue with brushes!
Due to the very nature of how the position demand is delivered, many cheaper servos will have a slight 'buzz' even when sationary. This can cause significant mechanical wear. The first thing to fail in most servos (excluding over stress dameage) is the position feedback pot. This type of failure manifests as 'glitching' and erratic behaviour which often causes the gears to wear very quickly which then get blamed for the overall failure.
If your mechanism can cope with being inactive when not moving, I would suggest dissabling the servos when they are not required.
Hobby servos are not designed for continuous use.