Hello ! I'm beginner electronical maker. I need to choose a motor for a project. I dont really know what type of motor will be good, but i think a classic DC motor with a incremental encoder will suit my need.

This motor need to :
- provide at least 8Kg.cm even at the minimum speed
- rotate at a speed between 0.5HZ and 5HZ when loaded
- be able to be able to go to 5HZ from 0.5HZ (and from 5HZ to 0.5HZ) in one rotation when loaded
- be able to do complete rotation
- be able to go at a start position
- cost maxi 200€

What do you think of this one with an additionnal gear ration of 1:2 and a magnet on the output gear to read the start position with a reed switch ?

 

How precise positioning do you need?
If it is very critical you would need some kind of PID loop control to obtain super accuracy, the encoder on the motor shown is a hall effect devices, so the pulses/rev will not be all that high.
At that fairly low rpm you should be able to stop fairly accurately and the GB provides some natural braking effect.
Max.

 

In positioning when i want to go at start position ? +- 5°, it's just to help the user to handle correctly the device during the setup process.

My fear is about acceleration, this motor will have enough power to to go from 30 RPM to 300 RPM (rpm seems to be the good unit here) in one rotation when loaded ? It's seems difficult for me because i have 8/8.5kg of my torque force used.

 

The torque output of the example unit is 17kg-cm. But will only go to 168rpm at the rated voltage of 12vdc.
Max.

 

Yes but i plan to add 2 gear with 2:1 ratio, it will multiply the speed output to 2 and divide the torque by 2. Like said in my first message without that the max rpm will be too low.

 

I missed the 1:2 reference in the OP.
Have you measured the torque required?
Max.

 

Not really, i use the high estimation of an other maker who has already made this kind of project. I will convert this rotational move to a linear one. I need the same thrust power of a saw blade.