Hi,
Last weekend I tested half of my servos for my Hexapod, just got around to do the remaining half today. But the problem that I have now is that the servos are jittering. I am using the SSC32, 645MG servos and a 6V 2800mAh battery. When using lynxterm and I click on All 1500 or give a command such as #3 P750 T3000 the servo jitters like mad. I have checked the voltage of the battery and it is reading 6.5V.
What could be wrong 
I have added a picture below.
the picture is fine. nothing wrong there.
have you tested a different pin and different servos? you only mention servo not servos. do all servos do this?
Assuming you are using 18 servos, you tested 9 of them and every thing was ok. Now are you testing the second 9 by themselves, or are you now testing all 18 at the same time? When you measure the battery voltage, you need to do the measurement when the servos are loaded.
I was testing two servos at a time, and I was trying them in different pins and this was when they were jittering.
I think I have the problem solved now, I connected four servos and they worked fine, I then connected all 18 and they all responded to my commands (except one I’ll explain this below). Were they jittering because they had too much voltage? I presumed the voltage regulator on the board has an output of 5V?
The one servo that wasn’t responding had a constant buzzing noise coming from it, it then got very hot so I removed it from the SSC32, I presume I have one faulty servo since its not responding and because it got very hot
If you are using a NiMh battery its recommended to use another battery for logic. (remove the VS-VL jumper). The voltage drop a lot when all servos are commanded at ones, that might trig a reset too.
Thanks Zenta i’ll do that. Would you know why my servos were jittering? When I had two servos connected they were jittering mad when given commands but when I connected four or more the problem went away and they worked perfect.
There are only two reasons for a servo moving inconsistent (apart from them being broken)
1: power
2: signal
Power has to be rather the same all the sime, whith no or low overtunes (small waveforms), and not to low
The signal is very important because the 645 are analog, this meens that the servo has no or allmost none errorcorrection on the signal, if there are a small disturbanse in the signal to an analog servo, it thinks “ok, i’ll go there instead of here”, but a digital whould think “i whont go there because the signal cant move that fast, it is probably an disturbance, Ill just stay where i am”
Supplying a servo with a voltage higher than its max rated voltage can cause jitter or eratic behavior. This may explain why the the servos jitter when only one or two are connected, but the problem goes away when more are connected, loading the battery and dropping the voltage.
Thanks PappaNiklas and zoomkat, Ya I know what you mean but I thought the voltage regulator on the SSC32 would have a constant output of 5volts as long as you were supplying 5volts or more to the board.
The 5 volt regulator is for the on-board logic. The servos are powered directly from the VS terminals. Btw, does the two servos jitter under load too? Monitor the VS under the jittering conditions. Also try the separate VS/VL solution first.
My input on this is… Although at very first the voltage from a 6vdc battery is around 7.2vdc, but this will drop to around 6vdc in a short time. It is acceptable practice to power a 6vdc servo directly from a 6vdc battery. When only a couple servos are connected to a large capacity battery, (2800mAh) it may take a few minutes for the battery to get down to the 6vdc area of the discharge curve. A voltage regulator capable of dropping the VS to 5 or 6vdc at a current that can power a hexapod (8-10amps) would be rather large, and would not fit on the SSC-32 board.
Thanks again Jim and Zenta for the information, I didn’t realize the regulator on the board was for the logic. The problem is solved, the servos work perfect when 4 or more are connected. No more jittering.
All going well I should have my hexapod assembled by the weekend.
