I have built an 3 dof hexapod, containing 18 645mg high torque servos.
The design is much like the standard 3dof-R hexapod.
When i issue some routines, (like the one which makes it stand up).
The SSC-32 recieves the command and starts executing it. But suddenly
it drops it and there’s no response.
Moreover, this doesnot happen always. if i give the command again and again, it stands up after a few trials.
I am using double battery connected in parallel, 2800 mAh NiMh 6 Volts.
Otherwise , SSC32 works well with fewer motors.
Another problem comes when i try to update the firmware, it is not able
to do so. It gives an error message “Check ur power source”.
I wonder what your voltage drops to when commanded to move the servos. It’s possible that it drops to a low level that is causeing this problem. how many servos are you using (im guessing 18 ) and what kind are they? You mentioned the ssc-32 works fine with fewer servos, how many is fewer?
Since the ssc-32 works fine with fewer servos, my guess is that the added seros is drawing more current than what the source can provide. Just a guess, dont hold me to that.
I had similar behavior from my 12-servo hexapod a while back.
After much head-scratching and note-checking, it turned out to be due to processor/controller brownouts from overdrawing the battery.
In working to reduce weight, I ganged everything together onto a single power supply, and it worked beautifully - while the battery was completely and fully charged. Even a slight dip in the battery, however, and I began to see the “bot fall down” behavior, often at the most inopportune times, such as demonstrating the robot to others. What made it maddening to troubleshoot was the fact that this was happening fairly close to a full charge, and the servos were simply drawing too much current for the battery and/or power supply chain. Put the bot on the workbench, and the battery showed a full charge, because it wasn’t being taxed as much as when it was operating in the field.
Switching back to independent batteries for logic and servos eliminated my problem, at only a slight increase in weight.
What you are describing is defenitely the SSC-32 resetting. After answering this same problem on the forum just yesterday I added the following information to the SSC-32 manual.
Troubleshooting Information
If you notice the servos turn off, or stop holding position when moving several servos at one time. This indicates the SSC-32 has reset. This can be verified by noticing if the green LED is on steady after the servos are instructed to move. The green LED is not a power indicator, but a status indicator. When the SSC-32 is turned on the LED will be on steady. It will remain on until it has received a valid serial command, then it will go out and only blink when receiving serial data.
The SSC-32 has two power supply inputs. The logic supply (VL) powers the microcontroller and it’s support circuitry through a 5vdc regulator. The servo supply (VS) powers the servos directly. In single supply mode (default) the jumper VS1=VL will provide power to the VL 5vdc regulator from the VS terminal. This works great for battery use, and with most wall pack use, as long as the voltage does not drop too much. However if it does drop, the voltage to the microcontroller is interrupted and the SSC-32 resets. To fix this you remove the VS1=VL jumper and connect a 9vdc battery clip to the VL input. This isolates the servo and logic supplies so one cannot effect the other.
Using the single supply mode is generally safe for the following conditions:
VS of 7.2vdc 2800mAh NiCad or NiMH battery packs for up to 24 servos.
VS of 7.4vdc 2800mAh LiPo battery packs for up to 24 servos.
VS of 6.0vdc 1600mAh NiCad or NiMH battery packs for up to 18 servos.
VS of 6.0vdc 2.0amp wall pack for up to 8 servos.
Note, these are just general guidelines and some exceptions may exist. The only other thing that can cause this effect is a poor power delivery system. If the wires carrying the current are too small, or connections are made with stripped and twisted wire, or cheap plastic battery holders are used, the same problem may occur. 99% of customers problems with the SSC-32 are power supply related. If you are noticing erratic or unstable servo movements, look at the power delivery system.
It helps me. So far I am not having this problem, but to be on the safe side I will make the suggested changes.
Previously I added a 9v battery and a second on/off toggle switch to run the ABB and Atom processor. Would you recommend using the same battery and switch to run both the Atom and the VL of the SSC?
It may be worth using a low voltage drop diode and a large capacitor to isolate the controller power supply from the main power supply to protect against momentary low voltage to the controller.
Thanx for the suggestions, now since i dont have a strong battery, i m going for a constant power supply. I think a 10A 9V supply will be sufficient for VS and VL both. Then i will also monitor how much current and voltages are being consumed, and then decide which battery to fix on it.
BUT I DID NOT GET ANY SOLUTION TO THE PROBLEM I M FACING WHILE
TRYING TO UPDATE THE FIRMWARE. IT GIVES AN ERROR MESSAGE “CHECK UR POWER SOURCE”
PLEASE TELL ME WHAT SHOULD I DO TO UPDATE MY FIRMWARE.
You can not use a straight 9V power supply for your servos. Most servos will take up to 7.2V, but some will only take up to 6V. You need to check the power requirements of your parts before you go plugging power into them. No servos I know of will take 9V.
It’s only for the servos that you can not use 9V for power. For the electronics, it is OK. You mentioned using 9V for both Vs and Vl, which means both servo and logic power. Vl (logic power) can be 9V. Vs (servo power) can not go above 6.0V to 7.2V - depending on your servos. Check the power requirements and restrictions of your servos.
It was assumed that the low power problem disscussed in great detail was also causeing your firmware update problem. If it didn’t I will try to help you more…
What baud rate are you using? It must be set for 115.2k to do the firmware update. If you changed it to 38.4 or other, it will not work.
Are you able to type VER and get a reply from the SSC-32?
You can use a 7805 voltage regulator with a diode to get 5.7v for the servos from the 9v source. I’d use one regulator per servo as they are rated at 1a each. I like higher voltage bench power supplies as they will have more power output capability than a lower voltage unit of the same current capability. I’ve have a schematic at the bottom of the brlow page showing the regulator/diode setup.
Regarding the question about getting a reply for the VER query, it works well
and i always get a reply.
But when i try to update the firmware, the procedure runs half the way and
then as soon as verfication starts, it gives the error message.
And regarding the baud rate, i m already at 115.2k , i dont think that’s a problem.
I will try doing the same as soon as i get my power supply
ONE MORE QUESTION,
if i use a 6V 10A power supply, will it be safe for the servos ?
Coz as mentioned, in the above post, each servo has a current rating
of 1A. In this case, at some point of time if all servos are drawing less than 10 A, then there is a chance that any one servo, out of load may
draw more current and get burnt up!
So tell me will it be safe or not.
if i use a 6V 10A power supply, will it be safe for the servos ?
Coz as mentioned, in the above post, each servo has a current rating
of 1A. In this case, at some point of time if all servos are drawing less than 10 A, then there is a chance that any one servo, out of load may
draw more current and get burnt up!
So tell me will it be safe or not.
Please try removing the VS1=VL jumper, install a 9vdc battery connector to the VL input and try the update that way.
Do you have another PC you try?
The timing for the firmware update is a little more precise than normal operation. I haven’t heard of anyone not being able to do the firmware upgrade.
but i m not using any usb to serial cable,
and yes i have tried updating from a different system also
it does not work.
The error message is about power supply.
I REPEAT THE QUESTION REGARDING SAFETY
Do i need to use 1 A current limiting resistance along with the servos in order
to ensure they dont get burnt up ?
Ok, the error saying check power supply is a general reply. What I mean is, it gives that response no matter what the problem is. I can’t think of ANYTHING that would cause this, and I have received no other complaints of this nature. I would be happy to test it here and replace it if it is defective.
I didn’t miss the question about safety. I meant to address it with the comment “The power supply should be fine” I’m trying to do my best. For a more complete explanation… There is no need to current limit the supply. Servos will draw the current they need to operate, and no more. If you attempt to limit the current to 1 amp and they require 1.2 amps, the voltage will drop and the performance will be adversly effected. I hope this helps, Jim
For a more complete explanation… There is no need to current limit the supply. Servos will draw the current they need to operate, and no more. If you attempt to limit the current to 1 amp and they require 1.2 amps, the voltage will drop and the performance will be adversly effected. I hope this helps, Jim