Hi, 

i know most people with InMoov has had one or two servos burn out on them and i been thinking on how to stop this, this is just another level of proctetion, but the idea is to install a temperature sensor in each servo and monitor them using th ADC on the arduino and when they get hot it gets turned off and maybe InMoov can tell you about it. 

to start off i needed a cheap temperature sensor and they don't come much cheaper than a silicon diode.

i found this page that explanse how a silicon diode can be used  https://www.openimpulse.com/blog/2012/07/low-cost-diode-temperature-sensor/#more-261

installing the didode in a mg946r servo.

after installing it i then ran some tests , due to the small voltage we looking at 0v to 750mv, a line needed to be added into MRLCOMM.INO "analogReference(INTERNAL1V1)"  to change the analog reference voltage from 5v to 1.1v more info about this is : http://arduino.cc/en/Reference/AnalogReference

once this is done and uploaded to the arduino, using the oscope, with  servo not running you get a nice flate line.

but with the servo running pass its movment point, its not so nice, 

but the lowest points could be used as when the servo heats up the voltage drops.

this is where im up to.

 

wvantoorn

9 years 8 months ago

what about the thermistor the repraps use? they are pretty stable, accurate and also very cheap, and you can use the bias tables from the marlin firmware. they also use the adc line i think from my head, and that would be an improvement to save the expensive 805bb's. But if the upgrade from adolph works in the shoulder and maybe the lower abdomen, that would save us from buying the expensive hs805's. At least a few of them!

 

I am currently printing the last parts for the lower abs, and want to use steppers in stead of servos, and use thermal protection!

So thank you Jhack, with this we can save our inmoovs!

kwatters

9 years 8 months ago

Nice work JHack.  Excellent suggestion. I was thinking about this problem too. Nice to see others are also.I've actually had servos get so hot that they began melting the PLA that the robot was printed out of..  eek!

It'd be nice to have the MRLComm.ino automatically detach the servo when the temp got too high...  Or even better yet, have the temp sensor trigger a relay to detach the servo..

I've also been a bit worried about input voltage surges or accidentally crossing + and - to the servos. I think a few servos have been burned on me that way also.

Servo mass grave.  Evidence of war crimes against InMoov nation.