SPEKTRUM DS821 Digital Servos Oscillate, Jerky

Help & Support Robot Parts
1

I built a Phoenix using some Futaba S3001 servos and it worked very well, I did notice that they seemed to not have much authority in the movements. So I replaced them with some Spektrum DS821 Digital servos and they do make a difference in the performance of the Phoenix. I have had so much fun with this thing I used Basic Atom and BOT Board for awhile then converted the code over to run in a PIC18F252.

I do notice the DS821 servos are jerky or they oscillate I can stop this by steadying the Phoenix with my hand but it will start up again when am at rest after walking. I did go through a lengthy alignment process using the Lynx Terminal.

I am testing this using a 12 volt 11 amp Bench power supply I use a separate battery supply for the logic I also tried my Lipo 7.4 volt battery. I am drawing a less than 2 amps through a Castle Creations 10 amp BEC. I placed a scope on the servo power side on the SSC-32 and its very smooth and consistent at 5.94 volts.

I was wondering if anyone else has experienced this or might have an answer to solve this. I would like to use these servos but if not I will get some of the Hitech HS-485 servos from Lynxmotion.

Thanks

2

I suspect your CC regulator is not keeping up with the servos demand. Phoenix should draw 1 amp at rest, but can demand 8 amp surges. If the CC regulator isn’t up to the task the voltage will drop and the servos will not act right.

3

Thanks for the reply, I will split the servo load on the SSC-32 board with two 10 amp BEC’s that I have and see if this helps.

John