It is long time can't figure out with suitable device, I need your help
I use 8 servo motors in my Arduino Uno with Adafruit Servo Shield project Power HD High-Speed Digital Micro Servo DSM44 and FEETECH Mini Servo FT1117M which is quite cheap and useful for my prototype assembly. DSM44 works fine, because it is small, fast and quite powerful, with taking into account that my mechanics acceleration requires a small mass, but there is two problems with DSM44, maybe because I have not permanent, but intensive load on motors, I'm really not sure about reason, possibly brush failure with intensive load and also almost servos is loud. I'm looking for suitable device which will cover most of specifics required for my device:
Speed: No less 0.07 sec/60° with 6V
Power: Torque no less 1.5 kg cm with 6V
It does not requires get feedback, as if I use smart servo, but must be digital, because degree position should operate in short ranges with high speed, so quick response, fast acceleration and accuracy is important
Small size: from 20x9x26 or less to 35x12x30 plus/minus 1-5mm max
Must be a quite, silent as much it is possible
Must be secure for not constant, but intense work processing of serial events
Control method uses Arduino Uno and Adafruit Servo Shield 6V 8A power supply, sanding of PWM degree value via serial port from C# desktop application , so controller sketch contains only receiver conditional function per each unit
Maybe I have to use some professional device, if it is possible to find something not very expensive, but here is a options that I try to understand and figure out what could be the best choice in my case:
Using of Brush Servo Motor and Brushless difference with my requirements, should I use Brushless motors instead
I'm thinking about ClearPath Servo Motor in terms of silence, however, the control method as available size of the motors is not entirely obvious to me yet, requires more research
As idea controlling of DC motors with some kind of shield for Arduino Uno controller, I'm not quite sure about device and assembly in this case, as well as on controlling multiple DC motors with PWM from Arduino with some suitable board like this Dual H-Bridge Motor Driver L298N, but something compact for 8 motors, 6V or high voltage powering requirement, rotation speed control, it must be DC motor position control system, if it is possible and suitable
Servo goes to correct or returns to initial position with load of controller sketch or from application, and keeps gear in the place. In my case important only go to same angle by received degree value, without position lost, so if each time motor moves to the same angle it is fine, then seems like it does not requires using "switch limit", if it will go to the same position, I guess it is not important to know in which position it was before shut down or was turned manually after.
Any advice, guide or example would be very helpful
Paul_KD7HB:
My only advice is to get rid of all the "not sure" and "guessing" then someone may be able to suggest something.
Paul
Hello,
Thank your for your feedback
I think my question is clear, I'm looking for proper device and solution by clearly listed requirements. If I was sure and didn’t guess I probably didn’t ask for advice, but yes, I'm "not sure" and "guessing", that's why I asking for advice. Don't you agree with that? Because, your current advice does not makes sense in my particular case, I should not ask anything at all, if I'm not sure
Geared servos are not quiet, the gears are spur gears which are inherently noisy. Filling the gearbox with grease will reduce gear noise, assuming there is a sealed gear compartment in the servo.
You seem to be confusing a servo with a servomotor. The clearpath servomotors are not servos like the ones you have, and will not replace one (as it uses an incremental encoder).
MarkT:
Geared servos are not quiet, the gears are spur gears which are inherently noisy. Filling the gearbox with grease will reduce gear noise, assuming there is a sealed gear compartment in the servo.
You seem to be confusing a servo with a servomotor. The clearpath servomotors are not servos like the ones you have, and will not replace one (as it uses an incremental encoder).
Hello,
Thank you for your feedback
I've tried to use grease, but result is not really effective, a bit less noise, but it is still loud enough and seems like particular servo is not secured with intensive load, possibly brushes failure
Idea on ClearPath Servo Motor is really superficial, because I've never used this device and did not research enough on it, would be good to figure out if I can use DC motor, control it as required
Servos have absolute position control. If you need this you need an absolute encoder, or other absolute position feedback device. The cheap ClearPath servomotors have as far as I can see only incremental encoders, so they basically can emulate steppers (but be much more efficient and go much faster). You have to home such a device at start-up so it can find out the current position. Your size constraint is a big problem.
A proper industrial servomotor (expensive) will have absolute encoder, brake, velocity feedback, multiple modes of operation and be much larger.
I think your best bet is a robotics grade servo with metal enclosure and precision gears, and pack the gears with grease - but spur gears are always noisy. If you can find one with helical gears that would help, but it will be expensive. Gears are noisy, you would prefer belt drive or lead-screw for a quiet machine.
I just want to pick up the comment on brush failure.
The brushes wear out as the motor turns. If the load is changing but the servo is stationary then the brushes aren't wearing.
Brushes can be destroyed by overheating but servos are designed to be operated at zero RPM, which overheats and kills normal motors. So, unlikely to fail.
Generally you would expect a brushless motor to be quieter but the difference is insignificant compared to gearbox noise. I think for your usage, both types will be equal.
MarkT:
Servos have absolute position control. If you need this you need an absolute encoder, or other absolute position feedback device. The cheap ClearPath servomotors have as far as I can see only incremental encoders, so they basically can emulate steppers (but be much more efficient and go much faster). You have to home such a device at start-up so it can find out the current position. Your size constraint is a big problem.
A proper industrial servomotor (expensive) will have absolute encoder, brake, velocity feedback, multiple modes of operation and be much larger.
I think your best bet is a robotics grade servo with metal enclosure and precision gears, and pack the gears with grease - but spur gears are always noisy. If you can find one with helical gears that would help, but it will be expensive. Gears are noisy, you would prefer belt drive or lead-screw for a quiet machine.
Some devices already includes integrated encoders, but the size of motor is too big, same with robotics servos or industrial servomotors.
Seems like I've to find some scheme with using of absolute encoder and use some proper DC motors in assembly, searching for suitable scheme and devices.
MorganS:
I just want to pick up the comment on brush failure.
The brushes wear out as the motor turns. If the load is changing but the servo is stationary then the brushes aren't wearing.
Brushes can be destroyed by overheating but servos are designed to be operated at zero RPM, which overheats and kills normal motors. So, unlikely to fail.
Generally you would expect a brushless motor to be quieter but the difference is insignificant compared to gearbox noise. I think for your usage, both types will be equal.
Hello,
Thank you for your feedback
So, brushless servo seems to be safer, but even if you don't care about the noise, it is not easy to find required size, speed and power device
Indeed, this is real engineering - bespoke components may be needed to meet all your requirements, off-the-shelf limits the options substantially for mechanical / electromechanical parts