Jittery servos at 6v and 7.4v but not at 5V

Lynxmotion Electronics & Software
1

Hello.

I am building a hexapod using an Arduino Mega, and a SSC32U.
I am powering the SSC32 from a 3S Lipo using a UBEC which allows me to change the voltage supplied to the SSC32 VS1 terminal from 5v / 6v / 7.4v.
Arduino Mega is currently powered from USB.

The servos I am running are these CheapIsh Robot servos from ebay, however are stated to be rated at 15KG. Working voltage is 4.8 to 7.4v.
They seem ok actually. No slop.

So far I have built one leg to allow me to get my gait and IK working. I started with 6v supply to SSC32.

I was getting extreme vibration in my leg during movement, especially at slower speeds, and I noticed that changing
the voltage supplied to the ssc32 to 7.4V made it even worse.

So I dropped the voltage to 5V and that seems to be much better, but i know that i am losing the top end torque and speed that these servos can deliver.

Can anyone suggest why i might be getting such vibrations and servo jerkyness at higher voltages, but not at lower voltages ?
Is it possible i can use a capacitor across each servo’s power supply to smooth the movements ?
Is it worth trying a seperate power supply to the VL terminal ?

Thanks
Martin

2

Hi,

You are using “no name” servos from ebay. It is impossible to know if it is related to the build quality of these servos. You can always try putting some capacitors on the power supply to see if it helps.
Also, is your UBEC also a “no name” product from ebay? If it is the case, maybe it is of poor quality and is not able to produce smooth voltage levels.

Best regards,

3

Having purchased 6 Dynamixel AX-12’s and found them to be sloppy and not fit for purpose I was looking for a better / cheaper solution.

These no-name servos are better, all be it that they don’t have the feedback. I was so disappointed with the dynamixel servos. I sent them back.

I have 10 years RC experience, but i have never come across servo’s that are happier on less volts.
The BEC is a quality 20A product from hobby wing and the voltage output is absolutely bang on. I have tested it.

Any other suggestions ?

4

Hi,

If you are able, try to contact the servo company. Maybe they will be able to tell you if there is a problem when the servos are operated at certain voltage levels.

We never had this kind of problems with the SSC-32u and standard servos.

Best regards,