Hi all,
I have a Hitec digital 5125MG digital servo. I’m trying to drive it with a Ferretronic FT639 servo cotroller chip via a serial line. I was not able to get a 180 degree rotation. The maximum i can get is a little bit more than 90 degree.
Does digital servo able to rotate 180 degree?
Please help!
Cheers
Is any modification needed to the digital servo in order to have a 180 degree rotation?
Please help, Cheers
The Hitec digital servos are capable of moving a full 180 degrees, but they have to be programmed for it using the HFP-10 servo programmer. It is not difficult, but the programmer is expensive.
On Most of the Hitec servo data sheet, it says that they are capeble of 360 degrees modification. Does anyone knows what is that mean? And any ideas how to do it?
Yes, you cut off the plastic/metal stops on the reduction gears.
However, once you do this, the servo is unable to hold a position.
It pretty much turns into a regular DC motor with an on-board speed-controller.
This is nice if you’re using the servos for a vehicle, but not helpful if your building a jointed robot.
Jim, I’m confused.
I never have used the servo programmer to get 180 degrees with the 5645 servos.
Is it only necessary for some servos?
Is this the only solutions? I need this feature to hold a position as I’m using the servo to drive some pressure gauge which required exact position.
Well, you can get 360 degrees of rotation with added gears.
A 2:1 ratio will get you the 360 that you need, but it’ll sacrifice half the torque.
This may not be an issue if you’re only turning a valve, though.
I know that Servo City makes reduction servo gearboxes, but they’re all 180 degrees.
You’d probably be stuck making your own gear/belt assembly.
Come to think of it, the Vex robotics kits have servos with gear outputs.
You can pick up an accessory servo and an accessory gear kit at your local radioshack.
You can probably use these servos with the SSC-32, but you should check with the people on the vex forums, first.
Thanks for the Vex robotics kits, but I’m having problem to fit 2 servos with gears or chain into a 100mm diameter gauge.
Can we make a 180 degree rotation using analog servo? Any modification needs to be made on the analog servo?
Cheers
Pending Jim’s response, I’d say that you’ll need the servo programmer (see Jim’s post above).
Both digital and analog Hitec servos are able to do 180 degrees (it’s actually more like 190-200 so that offsets don’t disturb the total).
Out-of-the-box, I can only say that 5645’s are capable of this.
I have no experience with any other servo models, though, so others may also not need the servo programmer.
Do you guys happend to know that what sort of signal that the programmer send to the servo in order to programme it?
Can we actually build one these programmer?
Hold on there… I just realized you are referring to the 5125, which is a “thin” servo. I’m fairly certain this servo can’t do more than the 90 degrees due to mechanical limitations. It can’t be modified for continuous rotation either. Sorry…
It is required. You probably never noticed the range limitation. In order to get the full 180 degree range you must change the left end stop from -100 to -200, and the right end stop value form 100 to 200. The result is 900uS to 2100uS will provide 180 degrees of range.
Any Hitec analog servo is capable of 180° range.
No Nick, I’m sorry, but you’re wrong. 
Aww, poop!
So that’s why my servos don’t want to go that last bit of distance.
It always seemed like I could turn them farther with my hands than they could be turned with the software.
Well, until I finish paying off my biped, 160 or so degrees will have to do.
At least the added range is the same on both sides, so I won’t have to reprogram the positions after I get myself a programmer.
Do you mean by physically modifying it, or just by using a pulse range outside the typical 1 to 2 mS range (w/20mS frame rate)?
The only servo modification that I am aware of is for 360° continuous rotation. All Hitec analog standard size servos are capable of a full 180° or rotation. This is acomplished by sending (approximately) 600uS to 2400uS positive going pulses that repeat every 20mS. Our SSC-32 makes sure the range is achievable by allowing pulses a bit beyond these values as each servo is a little different. The SSc-32 does 500uS to 2500uS.
Remember analog servos accept a range from 600uS to 2400uS, but the digital ones are set for 900uS to 2100uS regardless of the range they are programmed for.
By the way. This thread prompted Beth and me to do a quick tutorial on how to adjust the end stops on a digital servo. Check out the following link. lynxmotion.com/images/html/build100.htm
Not to be picky, but if you haven’t programmed the 5645’s they can’t move beyond +/- 45°, (90° total). I’m more than a bit curious why you are seeing 160°…
I think Nick was lying to you Jim. Hes not getting 160 Deg. hes only getting 90 Deg. But he wants everyone to THINK he’s getting 160…
JK 
