Questions about Continuous Rotation Servos
I am very behind the times for radio equipment. Are servo's still interchangeable between receivers? I am thinking about buying some Hitec HSR-1425CR Continuous Rotation Dual Ball Bearing Servos for Nassau. If there was any question if it would work I can just buy one for testing...
While I am asking questions... How well would servo's react to having their power or ground wire switched open (cut) while it was running? Could I use this to turn servo's on and off while rotating turrets? If so it would be easier than rigging everything up with steppers and a PIC.
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Re: Questions about Continuous Rotation Servos
Any brand of modern servo should work with most any receiver. The only exception is that Futaba puts a tab on one side of their connectors that someitimes has to be trimmed off with a knife to make them fit. I really wish Futaba would just use a standard connector like everyone else.
I generally like ServoCity better as they generally have more technical information and better prices.
http://www.servocity.com/html/hsr-1425cr__continuous_rotatio.html
As I suspected the position potentiometer has been removed. You should be able to modify most any servo for continuous rotation but widening the deadband to prevent creep might be tricky. You could cut the leads to the servo to stop iit but why would you want to? This servo is for all intents and purposes a really slow motor with a built in bidirectional speed controller. However, performance wise it is fairly mediocre for a full size servo. I think I would just put a similar servo on a three position switch and adjust the end points of that channel so that the servo rotates at the desired speed. Then when you want the servo to stop you can simply center the switch. You could also use a proportional channel to control it
If you are looking for great budget servos, Hyperion has a pretty good reputation and seems to make a quality product. They do however use the wonky Futaba style connectors. Allerc.com carries just about everything Hyperion makes. The DS20UMD would probably serve your purposes. These are "digital" servos so, continuous rotation modification may be more difficult because of their electrical speed and sensitivity. However, if you don't need continuous rotation, they do have an inexpensive (~$15) USB adapter for programming their servos. I may pick one of these up myself.
http://media.hyperion.hk/dn/at-ser/ATLAS-MAN-EN-PG1-DS16-DS20all.pdf
http://media.hyperion.hk/dn/pc/doc/ATLAS-PROGMAN-EN.pdf
Keep in mind that while the torque numbers are "smaller" the units are Kg-cm which is a much larger unit than oz-in. (20 (kg cm) = 278 (oz in))
CR instructions: www.societyofrobots.com/actuators_modifyservo.shtml
A great deal of the RC world is moving towards "HV" or high voltage. Many servos and receivers can run directly off 6.0v power and "HV" servos can run directly off a 2s (2 cells in series) lipo (3.7v/cell nominal 4.2v/cell full charge) or 8.5v max. In other words, If you are building a new ship today, you may not need a voltage regulator at all for your radio gear.
Re: Questions about Continuous Rotation Servos
We really need continuous rotation... I've modified a ton of servos for continous rotation and to be honest I am tired of it. However, super-gluing the pot is easier than what I have done... which is remove the pot entirely and replace with resistors... Next time I will try using glue - plus now I know I can drill out the gear at dead center!
I am hoping the Hitec HSR-1425CR continuous rotation servos will give me something that works well enough. I am thinking about order two tomorrow. If I do then I will post a review once I can experiment with them a little. I would like something a little smaller though... so I might get some standard servo and hack them for continous rotation...
BTW: Yes... I am putting a simple, crude, rotation system in Nassau. I have room for the servos, pulleys, belts, etc. It will not be anything fancy but it should work well enough. This is going to be worked on when other parts of the project are stalled waiting for material or parts.
Re: Questions about Continuous Rotation Servos
You could easily get the same performance as that hitec in a modded mini size servo. 42oz-in isn't squat. The trade off is that a mini that has that kind of performace is going to be at least $45. Just for example, the sub mini servos in my lepton produce ~60oz-in. I would be careful about drilling out the output gear because if the servo doesn't have dual ball bearing support then the lower end of the output spline will be essentially unsupported. Good news is that there are a lot of servos out there today that are dual ball bearing.
Yeah, pulling the pot completely sounds like entirely too much work. I think that using Hyperion servos is the way to go since their programmer is cheap and you could increase the deadband to eliminate drift and adjust the other parameters to get them working exactly the way you want them to. Not to mention that they have tons more torque than that wimpy Hitec. Just for comparison, the Hitec programmer is ~$200 while the Hyperion usb cable is like $18 and I just learned earlier today that their e-meter II (data logging system, ~$100?) can also program their servos. I'm still trying to figure it out but I think their servo programming cable can also be used to get data from their chargers and upgrade the firmware on them. I'll be honest, aside from their ESCs, I really like Hyperion's products these days.
Re: Questions about Continuous Rotation Servos
I should have updated this post a long time ago. I bought some of the Hitec HSR-1425CR servos. They work great except for one thing: they do not turn at the same rate. So if you want two or more servos to turn things syncronously these servos are not for you. Most people don't care; so generally they should be fine.
Re: Questions about Continuous Rotation Servos
New here and I know this is a rather old post. but the rotation syncronization is a problem I face a lot with robotics. several things can cause issues with syncing the servo. the main issue i've ever encountered is a mild resistance in the wiring harness to the servo. the on-board electronics don't have a very stable voltage regulator. check the harnesses and the driver motors. if there is more wear on the brushes they will also have a varried rate.
Hope this helps anyone else who might have the same issue.
Re: Questions about Continuous Rotation Servos
Thanks Jay. These were new servos, just out of the box, on a new y-connector. It was about as 'best case' as it gets. Things would only be going down hill in an actual boat with varying length leads and constant exposure to moisture. They are still a great product - people just need to assume the rates will not match.