I also have the Myoware muscle sensor, the Arduino, plenty of wire, and have purchased a 12V battery. I was beginning to muddle through adapting the code to replace the servo with the N20 when I stumbled upon some information that indicated that I may need to add a magnetic encoder to the motor in order to use it with this setup.
I found a Pololu encoder on Robot Shop that seems to be made for an N20. Will it work with the N20 I have, even though it’s a different brand? Is there anything else I need to make this adaptation? I noticed other people were using some sort of controller or driver as an additional intermediary. Is that something I’ll need? Thanks!
And I should mention that I’ll be replacing all the 3D-printed parts in this kit with a new design I’m making that will work with the style of motor (basically using a rubber band connected to the rail on the claws and the area where the claws exit the glove, so that when the motor unspools, the claws will quickly extend).
Fair. Okay, I see the longer shaft there. Are there encoders that would work with what I already purchased? I need higher torque than the motor you linked, and had a really hard time finding any other N20 that seemed like it might be feasible.
Also, it seems like I will probably need a motor controller for this project? I’ve seen the DRV8833 recommended, as everything I use needs to be really tiny, to fit inside a bulky glove, but those seem to go up to only 10.8 V. Will that be a problem with a 12 V N20?
Finally, I thought I had the battery figured out, but looks like somehow I ended up with something way under 12 V, and honestly much bulkier than I had in mind. Does anybody have recommendations for a tiny 12 V battery? I understand it might not be as small as the motor, but the smaller the better. I would rather use something rechargeable, but I’m open to disposable if the size difference is substantial enough.
I am not sure how to attach any encoder without the extended shaft. But, you can go here on the Pololu page and find the same motor you have but with extended shaft:
If you scroll down, you will see a table where you can choose voltage, RPM, torque, type of the motor and then you can find the SKU and order this motor. Some of these are also sold by RobotShop.
For the driver, something like this for a single motor should work:
And for the battery, it depends how much capacity you need? What are the size limitations?
I appreciate all the help! This is a difficult development in the project, though. I thought I had finally found the right motor, and nothing on the Pololu site is especially comparable to 1.5kg.cm rated torque at 500rpm. Let me ask you this. If I don’t need extreme precision, is it possible for me to use an Arduino to control the motors I already have without an encoder? I’m wholly inexperienced here, and learning while doing, so I don’t know if it’s possible to just pulse from the Arduino for a split-second to have the motor go forward and a split-second the other direction to have it wind back. It seemed like the encoder was only to control the rotation with precision.
The MP6550 looks great. Thanks for that! Are you able to give me the quick and stupid explanation on what the motor driver does and why it’s necessary?
As for the battery, I’m flexible on capacity, but obviously the higher I can get this without significantly increasing its profile, the better. This would be part of a costume that might sometimes be worn for long periods of time. It wouldn’t get activated very often, but it would still be ideal to completely negate any risk of needing to charge in the middle of a convention or something. I don’t have specific size limitations yet, because I’m designing the frame of the device around the hardware I need to make it work, but the smaller and flatter, the better. It could be long, potentially as long as 16cm or so, but it would need to to have a height and width (or diameter) no greater than 12mm or so, as it couldn’t extend off my arm any more than the N20.
@bennroe if you want to run motor precisely to a certain position, you would need an encoder. Otherwise, you cannot know where the motor is. But if you don’t need precise position, just simple rotation you can work without encoder. Apply voltage on the motor, it will run, cancel voltage, it will stop.
Motor driver is usually needed to control the motor via microcontroller but when microcontroller is not able to control such big currents or voltages. Meaning, bigger motors you cannot connect directly to Arduino for example.
Regarding the battery, maybe you can have a look here to get some impression about the size:
All right. I’m back on trying to make this happen. I’m thinking I should probably use the encoder and motor driver after all, but I’m still struggling like hell to find a motor with an extended shaft that has comparable torque and speed to the ones I originally bought (rated torque 1.5kg.cm and no-load speed 500rpm). At a comparable speed, those Pololu ones are showing extrapolated stall torques under 1kg.cm (which, correct me if I’m wrong, is probably closer to a rated torque of .25kg.cm). Does anyone have a line on N20s with extended shafts (ideally with back-connector encoders included) and comparable torque and speed to the ones I originally bought? I’m not picky about voltage, as long as it doesn’t exceed 12V, and will figure out my battery accordingly with the chosen motor.
On the note of batteries, though, 6V J batteries seem like they have a great profile for this project. Does anyone know what sort of connection I would use to connect J batteries to the device? I’m having a hard time figuring out what words to use to figure this out on my own. Thanks!
I see there are high torque N20 motors with encoder already installed.
Regarding J batteries. I see they were used in medical devices, old cameras, phones, etc. But not used very much anymore. Although, they can be a good choice is space for battery is very restricted. I guess you would need to have a slot for this battery card (something similar like for microSD card), but I did not find where you can buy this slot. In the end, I guess you can solder your contacts directly to battery terminals.
