Hi Pololu friends,
I use different digital servos on my Mini Maestro, a total of 6 servos, to control the landing gear doors of my C-123 and basically it works. However, my micro digital servos burn up after a short time at servo output 3 and 4 I have already burned 3 of them and before I continue to burn my money, I am looking for causes.
The supply voltage is 6.18V which should be ok but the servos hum, squeak and creak in every position, they are not even under load and there is no tension voltage, no pressure on the linkage.
But the result on the Mini Maestro was the same. I tested them via the Pololu Maestro Control Center, WITHOUT load on the linkage and at the slightest touch on the servo arm and in any hold position they creak, hum or squeak, get hot after 1,2,3, minutes and burn up. Unfortunately I noticed it as it was too late.
Something is not right at all but I don’t understand it ? … Does anyone have an idea, an explanation of what this can be?
Can it have something to do with the control of the Mini Maestro? Are there parameters that I can adjust? On the one hand, it can’t be that these digital servos hum and squeak in practically every position and on the other hand, they shouldn’t burn off at all … should I use analog Servos instead?
Using analog servos instead of digital, that could be an option, but it’s important to ensure that the analog servos are compatible with the Mini Maestro and that they are rated for the same voltage and current as the digital servos you were using.
I suspect that these cheap, digital micro servos have a problem holding a position and being constantly triggered. Therefore, the high-frequency squeak. If now in addition the motor runs constantly to adjust the position and that even with the maximum permissible voltage of 6V such a tiny servo pretty quickly burns up.
I do not know if the Mini Maestro can influence this, but I suspect not. A digital servo should hold its position in Hold, regardless of whether a force is applied or not. So it is rather a design problem of the servos.
Til now, I have not found any digital servos that do not squeak. also my digital, bigger standard Hitec servos are squeaking and they are controlled by a Jeti Central Box … but they don’t burn up.
Is there a technical specification of what requirements analog servos must have to be used on an Mini Maestro? I have ordered these analog servos for testing and will report the results.
There is no special specification that a servo needs to have to be used with the Maestro, aside from accepting standard hobby RC servo signals. I agree that it sounds like those particular servos are probably poorly tuned, causing them to try to move the motor back and forth very rapidly instead of settling at the commanded position, which quickly wears out the motor. It is not unusual for digital servos to draw more power than their approximately equivalent analog counterpart, but a good quality one that is well tuned from the manufacturer shouldn’t burn itself out just trying to hold a position when operated under recommended loads (which is generally around 20-25% of the stall torque).
There is no adjustable parameters to help this from the Maestro side; it is just sending the specified pulse width. However, if you do not need the servo to actively hold its position between movements, you could try sending a target position of 0 to turn off the pulse widths from the Maestro, but please note that some digital servos will continue holding the position of the last valid signal received.
I got the analog D-Power AS-225BB MG servos, plugged them into the Pololu Mini Maestro and they run smoothly, no hum, no squeak and steady. Interestingly, they hold their position even under load. That was actually the reason I originally chose digital servos. In the modeling world, digital servos have been around for many years, and of course they have their uses and I’m not saying you can’t use digital servos on the Pololu Mini Maestro … but from my point of view and for my purpose, analog servos are clearly better, without a doubt.
I am very relieved. One big problem less and I can finally take care of the choreography of all components.
I have already burned 3 of them and before I continue to burn my money, I am looking for causes.
? … Does anyone have an idea, an explanation of what this can be?
