I’ve noticed while searching for additional servo specs that Lynxmotion specs the HS-475HB and HS-645MG Hitec servos as having a 180 degree operating angle, while Servo City specs them at only a 90 degree operating angle? I have and use the '475 servos, I know they do 180 degrees, or nearly so. What’s the difference? Have Lynxmotion servos been modified or specially prepared? I’d rather buy them from LM anyway.
I also ran into the fact that Futaba 3004 servos turn the opposite way 'round! Very perplexing when replacing the Futaba knee servos on Loki with Hitec '475s. Loki walked, but backwards! Well, kinda. I still haven’t figured out what he was doing.
All better now. Added two lines of code to “flip” the Position command of the knee servos. I’ll get around to swapping out the shoulder servos later. with a little more code, I will be able to select between Futaba and Hitec servos with a jumper.
if(ServoNbr == 0 || ServoNbr == 2) /* "FIX" for reversed Knee servos */
Position = 3000 - Position;
The below is from the servo spec for 45 deg rotation. A pulse change of 1500 to 2300usec may well produce 90 deg rotation (which it probably does in real life).
Direction: Clockwise/Pulse Traveling 1500 to 1900usec
Yeah, 5645 says the same. I did now see a 180 option for an additional 10 spot. and the 311 states them the same.
2300? May be. But the “options” suggest they’ve modified them, as for the continuous. I get the continuous, maybe there are stops that have to be removed for 180 operation as well?
Don’t these these R/C servos have some sort of standard? I was able to verify that the '475 and the 3004 that I have access to rotated the same for a pulse width within their range. I’ll do some additional tests later (getting ready for “Yuri’s Knight” at NASA (Moffett Field, CA), I’m taking Carol my wife, and my two 'bots, Loki and Shelob to show.
If they are charging $10 to get a standard analog servo with 180 degree rotation, then they are ripping people off… they are 180 degrees out of the box. I’ve been using them for years in RC cars (mostly the 645). All of the standard hobby servos use the same pulse ranges; otherwise they would be useless in RC applications.
The shorter range of the digitals is intentional because they can be programmed, which means you have to buy the $150 programmer. The analogs can’t be programmed, so obvisouly Hitec can’t sell RC hobbyists useless 90 degree servos.
I’m not really a big Hitec fan at this point. The 90 degree thing bugs me. Their HMI protocol is crap. Robotis is kicking their ■■■■ in the hobby robot space, period.
Don’t confuse analog and digital servos. The servos in question are analog servos. Businesses that buy large amounts of servos might have them made special, or have a second party perform mods on the servos (Lynxmotion offers a continous rotation servo). These servos could probably be modified to do the intended functions. If the servos use the usual 5k pots, then removing the pot and replacing it with two 2.5k resistors, and removing the gear hard stop would set it for continous rotation. I’ve never tinkered with reversing direction or changing range, but this probably could be done with various pot modifications.
Well, I have no reason to order from them, other then maybe the PayPal connection. Used to be a good way to spend money that I made from my Steam engine plans.
Yeah, that makes sense for them to be the same. But after swapping out Futaba servos for new Hitec servos and the gait going really bad (and the day before a show as well), I’m now suspicious. Only the direction was backwards, no big thing if one knows about it, but it looked like I had a different angle per pulse width, and I didn’t have time to re-do half a dozen gaits.
That’s a real trick. A good reason to stay with simple analogs.
90 degree servos could be of use in airplanes. I don’t think bell cranks can use much more then that. I could be wrong. But then I’d want the full resolution in this range. Or maybe they don’t need it.
I’d rather just use simple DC servo motors (not R/C servos) in that case, and add my own servo electronics.
I can see how the mods for full rotation could be done easily enough. And reversing the direction can’t be too hard, simply reverse the servo leads and the pot leads, something like that.
I just want to get a good 180 out of a servo. I’m OK with the ones I have. But I suspect there are some “traps” out there. I’d hate to see someone buy servos for a 'bot, and not have them work. Other then junk servos, has any complaints come up in robotic use?
Sure, there are applications where 90 degrees is plenty. But transmitters have End Point Adjust, so you can always make the range smaller. No reason not to ship from the factory at 180 degrees… unless you’re trying to sell servo programmers that is.
Wow… a 475 is a 475 from me or anyone else. Same for any other Hitec analog servo. We are in the trenches making hobby robotics accessable at the component level. We’d like to have your servo business. We try harder and I think we deserve it. But the truth is there is no difference between Lynxmotion analog servos and servo cities. We list them as 180° capable, because they are. You just need to send an expanded range of pulses. Here is some additional information. lynxmotion.net/viewtopic.php?p=33232#33232
When I read this thread, I was under the assumption that the pages meant +/- 90 degrees, but having clicked on the link, the diagram on servo cities’ page clearly shows that it is +/- 45 degrees with an additional $10 for a 180 degree rotation. I found that intriguing, since I have 18 645s and have always noticed the 180 degrees. I’m wondering what makes these 645s only 90 degrees of rotation. I wonder if it is some sort of a gimmick or perhaps it is some special lot that they bought…
Anywho, any of the analog servos that I’ve bought at Lynxmotion and Tower have always been to the default specs of 180 degrees of range.
I love marketing terms, “ultra torque” for a 133oz-in servos. These servos barely met my application when I used them in my 4WD 1/10th electric off-road buggy. The Hitec HSR-5990TGs and Robotis RX-64s are “ultra-torque” IMO. Again, it’s just an opinion
yeah, That’s what I’m talking about. I went to ServoCity to find additional specs for the servos I have (24 so far from LM), an they are advertising them as ± 45 degree servos. For several models. Extra charges for 180 models and continuous models. Now I get it for the continuous revolution mods, they essentially “cripple” the servo by removing the stops and apparently disabling the pot feedback. But what (if anything) do they do for 180? Are there several errors in their pages, or are they charging $10 extra for nothing?
I can put up with the marketing hype like “ultra torque”. I went there for valid information, and hard to find parts, not tricks. I understand the limitations of “consumer” products, and I can live with that. I can even deal with getting servos with reversed rotation, or varying ranges of motion (hopefully one finds that out before buying 10’s of servos), but It would be nice to know ahead of time what is “basically the same”, and what is not. Especially if one is going to make recommendations to others!
Sigh… They charge $10.00 to either change a servo to CR, or program a digital servo for 180. If their website is so goofed up that it’s allowing that option to appear on an analog servo then I guess they are charging $10.00 for nothing.
I hear there is some way to add resistors to either end of the pot to give the servo increased travel. Thats the only reason I can even imagine they would charge money for 180 degrees. So, that would give their ‘180’ servo the ability to do 180 degrees of travel over a pulse range of 1100ms to 1900ms, whereas the unmodified servos will do 180 degrees over a pulse range of 500ms to 2500ms (the free way that the SSC uses).
The only reason you would want to use the ‘ServoCity’ way is if you have RC equipment that only generates pulses in the 1100ms to 1900ms range.
If you have a SSC (which you should!) then don’t waste your money.
a 475 is a 475 from me or anyone else. Same for any other Hitec analog servo. We are in the trenches making hobby robotics accessable at the component level. We’d like to have your servo business. We try harder and I think we deserve it. But the truth is there is no difference between Lynxmotion analog servos and servo cities. We list them as 180° capable, because they are. You just need to send an expanded range of pulses. Here is some additional information.