Type of coupler needed
Hey all I would like to know what type of coupler I would need for this type of servo ?https://us.banggood.com/Wholesale-Warehouse-JX-PDI-6221MG-20KG-Large-Torque-Digital-Coreless-Servo-For-RC-Model-wp-Usa-973947.html
https://i.stack.imgur.com/nZmaZ.jpg
The specs is this:
https://i.stack.imgur.com/VGT0S.png
I'm guessing that the **25T** means it has 25 teeth in the part that holds the adapters?
So I would guess I would need something like this?
https://i.stack.imgur.com/OJ8Zg.jpg
But I also would like to know what **size** those are called for my servo. I've seen them advertised as 5mm to 8mm. 6mm to 8mm, etc etc so I don't know if those are going to work? Some also just have a smooth round hole without the **teeth** and I'm not sure if that's something I could use as well?
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Re: Type of coupler needed
What are you planning to use these tiny little servos for? They were designed to run RC toys, and they're really small, weighing only a couple of ounces or so. I suppose you could power a very small CNC machine with them, but it doesn't seem worth it, considering that you'd have to come up with a power supply that put out current at 300hz.
It looks like they're set up to run a timing belt, but you can probably pull off those pulleys and use any coupler you wanted.
[FONT=Verdana]Andrew Werby[/FONT]
[URL="http://www.computersculpture.com/"]Website[/URL]
Re: Type of coupler needed
They are set up to run control arms like the ones pictured in the Bangood ad. They are not continuous. Most RC servos rotate +-45 degrees, some rotate +-90 degrees. They are controlled by a digital signal input. The input is like PWM, but not exactly and the duty cycle of the signal dictates the rotation position of the output shaft. Standard PWM works on most RC servos. If you are looking for these to turn continuously like a stepper motor, they don't. Some cannot even be hacked to rotate continuously because the gears are made such that they would mechanically limit the amount of rotation that could be achieved. There is usually a potentiometer inside that is used as the position feedback and they have a mechanical limit too.
Re: Type of coupler needed
i am modifying them in order for them to turn constantly.
Re: Type of coupler needed
It hardly seems worth the effort. If you need a small servo to run a CNC machine, just get a regular dual-end DC motor that's powerful enough for your needs that will run off a normal transformer, and put an optical encoder on the back.Originally Posted by tdgcnc
[FONT=Verdana]Andrew Werby[/FONT]
[URL="http://www.computersculpture.com/"]Website[/URL]
Re: Type of coupler needed
The general name for that kind of shaft is called a spline. Every manufacturer has their own spline profile, so you need to identify which spline the servo uses and then see if anyone sells a compatible shaft coupler (ex: https://www.servocity.com/servos/ser...ments/couplers ).
In most cases it is difficult and expensive to source an appropriate shaft coupler so its easier to make something that connects a shaft to one of the existing plastic arms instead. You could also trim down an arm to leave only the female spline and glue it into a coupler.
Note that if you modify a servo for continuous rotation you will no longer have position feedback and they become nothing more than a low-cost gear-motor.
Re: Type of coupler needed
If you are dead set on this plan, why not just use one of the control arms that comes with it and screw the arm to an appropriate coupling for what you are connecting it to.
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