I’ve been researching servo controllers for my next robotics project which will involve at least 15 digital servos and liked the specifications for the SSC-32. I will be using the HSR-8498HB digital servo.
Does the SSC-32 work with digital servos and how can it be used to get current/voltage/position feedback from the servos?
Thanks,
Aaqil Khan
Yes, the SSC-32 works with all the digital and analog servos sold by Lynxmotion.
You can not get feedback from the servo through the SSC-32.
8-Dale
“You can not get feedback from the servo through the SSC-32.”
You can get servo position feedback from a servo using the ssc-32 by using a simple servo modification like below.
I don’t think the original poster is talking about modifying servos. That modification may not even apply to the HSR-8498HB servos he will be using. Are you familiar with the HSR-8498HB robot servo?
I don’t think modifiying an HSR-8498HB would be reasonable, especially considering it can already give the desired feedback via other means.
8-Dale
does any canned servo controller other than (I am assuming) the one on the robonova actually have the ability to read position information back from these? Just to be clear I am not talking about a programmer, I mean an actual servo controller you would include on a project.
None of the commercial servo controllers I have looked at make use of servo feedback features.
8-Dale
This is promissed by Mike D. for the new controller he is working on for me. He is expected to have it completed early next year.
I think this points up some of the issues with “digital servos”, beyond them being 2-3 times more expensive than standard servos. One should some homework and make sure a digital servo will actually provide some advantage over a standard servo, and that appropriate controllers are available. That being said, the hsr-8498h spec says “Potentiometer Drive: Indirect Drive”, indicating it uses a pot for internal position feedback which probably could be tapped for info if needed.
I remember a while back Jim saying that digital servos have more resolution vs. standard servos and because of this, it has more turning power, not necessarily more torque if that makes any sense.
I look forward to the new servo controller with position feedback! Wooo Hooo! 8)
That’s holding power. Digital servos try harder to hold a position. An analog servo can be 15° off when under a heavy load, where digital servos never stray more than a few degrees.
actually indirect drive potentiometer on a servo is not a good thing as you get backlash in the gears which becomes a position error. What it gains you is probably better bearing support on the output shaft so the servo is more rugged. Ideally though the position feedback potentiometer should be directly mechanically coupled to the output shaft of the servo.
Hold on thar Eddie, your missing the real meaning of that spec. The potentiometer connects directly to the final gear in both scenarios: Indirect drive means the final gear has bushings or bearings that support the load applied to the final gear to the body of the servo. Direct drive for them means the potentiometer IS the bearing component. Let me tell you a story about a servo called the HS-300… 
When abused (as we do in robotics) the load on the final gear could after a little break in, cause the pots wiper to lose contact with the resistive element. Talk about walking robot sadness. weeping weeping 
Way too much “hanger flying” going on. I propose some actual testing be done comparing actual analog vs. digital servo performance. Would be a good “educational” introduction to scientific methodology for the younger crowd. Most of the “facts” being presented appear to be somewhat slanted and based on speculation instead of demonstrated facts. I have a cheap TS-53 servo sitting here with the pot completely removed for continous rotation and it still works. I guess it must be a high end “indirect drive” pot servo. Analog servos can be off 15 deg under load. So how far off is a comparable digital servo under the same conditions? 1 deg or 14 deg? As to resolution differences between digital and analog servos, where does that data come from? I haven’t seen any such data given in the manufacture’s specs for either type. I think a “bamboo skewer” resolution challange would be an easy start, as I’ve already done this and it is very simple.
Hi Jim Frye,
So there’s no way of getting feedback from the HSR-8498 using the SSC-32? 
How come theres no servo controller out there that utilizes hitec’s HMI protocol, considering the growing popularity of digital servos?
For my new robotics project, I really liked the specifications of this servo and its unfortunate that after investing so much in them, I can’t really utilize them to their fullest. Although, I appreciate zoomkat’sidea of dissecting the servo and getting analog info from the POT, I dont want to hack 15 expensive servos.
Um, ok. I am guessing from your description they have, um, adjusted the terminology from what you would expect it to mean in an industrial setting to simply mean the potentiometer bushing is not load bearing? So long as the potentiometer is not geared indirectly to the output shaft that should be a great thing. Do they use a shaft coupler or something? Personally I’ve never taken apart a $100+ servo 
so… I’m just working off terminology in how it’s applied to things other than hobby servos.
Actually I don’t think I even own any $100 servos but I digress… 
That was zoomcat’s idea, not mine.
8-Dale
We are developing a servo controller for them. Remember the 8498’s are a non-standard form factor. That didn’t help. And they aren’t really that old, under two years. The 5980 and 5990 servos have only been availalbe since about the middle of this year. It’s coming.
You probably need to look at your project and determine just what benefit you expect to gain from servo feedback. A lot of people talk about how great it is, but nobody I’ve seen in this forum is actually using it even though it is fairly simple to obtain from standard servos.
Maybe I didn’t give enough information about my robot. Its going to be completely autonomous, capable of navigating on its own and will be designed to adjust its quadrupedal movement based on terrain. It is vital for an autonomous system to continuously monitor its health (system voltage, current drawn by motors, servo position and load on servos among other feedback voltages from sensors etc.
So its not a matter of “benefit” - its a matter of utilizing 100% of what’s available to make my system as autonomous and failsafe as possible. My only intent with posting this question on this forum was to find out if anyone out there made any servo controllers which tap into this useful feature of digital servos. In particular, I liked the specs of SSC-32.
If you already bought the servos and nobody makes a controller for them, then you are some what between a rock and a hard spot with your project unless you can return or sell them. Take a look at the mythical “open servo” schematics and see how the servo data is obtained. With some electrical tinkering, you probably can use a similar setup to get the required data from your digital servos and an ssc-32. These types of projects are not always plug n’ play easy, but can be done. From the below, looks like the bottom of the servo comes off easily. I suggest you take the bottom off of one and see whats going on inside.
