Hi
I recently purchased the SSC 32 for a biped that I am making. I am using it in tandem with a Motorola processor which sends the commands to the SSC via a serial port.
I have connect 26 servo motors equally disdributed on both VS1 and VS2. But, when i try and send out signals to all 26 at the same time, the servos power down for a brief period of time , and then restart.
The thing is, I dont think it is a power problem as only some motors are deriving their power from teh SSC board. The rest are being powered externally. The Motorola processor also shows no signs of resetting during the time the motors power down.
What is the maximum number of motors that the SSC can provide signals to at one time/in one command.
I have scoured this forum but have found no such related quesiton.
Am at my wits end.
Any suggestions? Please help. Would appreciate any assistance.
I had removed the VL=VS jumper and was powering the controller through a separate Li-Pol using a 6V regulator. Is this sufficient to drive the SSC to full capacity ? The motors power down only when the signal is being sent to a lot of motors at once.
so long as VL=VS1 jumper isn’t installed it should be. actually if it’s only a 2S li-po you don’t need to pre-regulate it as VL can be up to 11V if I remember correctly. Once you initialize the servos to some position I don’t believe the SSC-32 VL power input requires any significant difference in power between commanding a couple servos or commanding all 4 banks at the same time… it’s pretty much running the same loop non-stop.
how about if some of the servos are not connected? the thought is to verify there is no other problem hiding behind what appears to be a power issue. I assume the servos are going through some sequence. Plugging half of them in and verifying they move correctly reduces the power level and lets you verify the commands were properly received and executed. If that works with 2 or 3 different sets of “half” the servos then it would suggest some other less obvious type of power issue. some things to consider may be some sort of ground loop or too small AWG wire from the servo power supply, or sharing power ground path with signal ground path (although the last one is a pretty extreme situation).
Are you also using separate VS1 and VS2 supplies, or just a single supply and the VS1=VS2 jumpers installed?
Can you go into more detail of your wiring? I suspect you are only using one battery to power both VS servo voltage, and VL logic battery. Definitely lose the 6vdc regulator on the VL side…
I am using 3 Castle creation BEC ( set at 7.4 V), all parallely connected to a 4000mah 2 cell lipo .
This BEC has a 5amp continuios and 10 amps peak rating each.
I have checked live performance through a Eagle tree V logger and found that the peak amp pull from the batteries is 13 amps and drop in V is max 7.4 .
Detailed wiring description :
I am using 26 5990TG (14 in the legs + 12 in hands).
Power from the lipo is divided into 3 BEC and then shorted together again. ( this i did so that all the amp drain is equally divided ).
all the leg servos are given +V and GND from another daughter board . one set of +V and Gnd is then taked from the daughter board to the SSC where the hand motors get power. thus on the ssc 32 only signal and power to the 12 hand motors is given.
Will it make a big difference if i continue using the 6 V bec for the logic , as i use this as power supply to my new micros ISOPOD which gives the stored servo positions to the SSC also .
Preparing to participate in robogames, so currently in a big soup!
According to the CC BEC FAQ, question number 5, the answer is you can’t do this without a isolation diode. castlecreations.com/support/faq/faq-ccbec.html#ccbec5
You can feed a BEC into the VS1 port, another BEC into VS2 port, and the third into the VL port… removing the VL=VS and VS1=VS2 jumpers entirely. You may not meet your peak current requirements however and cause the CC BEC to shutdown. I guess it might depend on how much of the 13A is being consumed by the SSC-32 VL and your controller.
Are you saying that the voltage drop does not go below 7.4v, or that the span of the drop is 7.4v? If you are pulling 13a with the voltage dropping to near 0, then there is a serious power supply problem. The no load running current of the servos per the spec sheet appears to be .38a, with a stall current of 4.2a to 5.2a. Starting all servos at the same time would give an amp pull somewhere between 9.88a and a potential 109.2a. The quick answer may be to not start all the servos at the same time, or find a “rest” position for the bot to be placed in that would have a minimum current draw, and then power the servos up to this rest position so there would be minimum curent draw from the servos. Another issue might be that the servos are digital. You can preclude the voltage drop on the ssc-32 in various ways, but the chips in the servos are probably powered from the servo supply voltage, and issues might arise when the servo supply voltage drops below the minimium 6v in the servo spec sheet.
Never ever thought it would be a power problem ( especially with the BEC, i thought putting 3 in parallel eliminated any problem possible due to over drain.) i used to break down my moves as i thought the controller can’t handle giving so many single changes at the same time!
I would now also check the ‘V vs t’ & 'A vs t 'on the output side of the BEC.
To save time due to a lot of rewiring needed ( have cut the wires short to reach the daughter board only). Can i simply put any common diode between the +V output of the BEC ( for all the three ) ?
Thanks
Today i understood when most of the support sites say that 90% problems are power problems! Always thought i was the 10%
