I am very new to hobby electronics and am in a deployable structure project where I need to wind up a cord that will be under increasing tension as its wound up and then also to unwind it on command and im not sure which type of motor to use because it seems that some servos can only move through a certain degree range
I am thinking about getting a sailwinch servo but am absolutely looking for recommendations
Welcome to the forum
What you are calling a continuous servo is not really a servo at all. Would a motor and gearbox do the job just as well ?
What maximum torque is needed?
A continuous rotation servo can't be programmed to hold at certain positions, only the speed and direction of rotation can be controlled.
Sail winch servos are limited to some small number of rotations, usually 2 or 3 complete rotations. For more travel than that, most people use a brushed DC gearmotor and shaft encoder.
Please put some speed numbers on your description of your project. How fast do you want the cord wound and how fast to unwind. Do you want enough torque to break the cord, or do you need to know the torque level and stop winding at some tension?
there is no speed goal but we're expecting to be working at less than 0.1 m/s deployment and retraction speed , the main goal is to turn the motor continuously, retracting a set of chords until the structure is completely deconstructed and then letting the chords out slowly, letting the internal tension of the system redeploy the structure
And do envision some sensor that will detect this or what?
so a DC brushed motor will be able to spin continuously? we do not need to measure the position of the motor, it just needs to be able to spin CW and CCW on command and then hold steady when needed
Of course. What else would you expect it to do ?
the initial plan is to manually determine when to stop i.e. some form of a a start/stop command when the structure is deployed/retracted to the point when want and once the deployment/retraction system is up to snuff we'll find some sensor system to determine this, the biggest thing is just making sure the motor can retract the chords and release them, and then hold steady when we need, were not really worried about the motion knowing its exact position
Limit switches at the top and bottom of travel may be all you need.
For example: https://www.amazon.com/JANDECCN-Switch-Straight-Action-V-153-1C25/dp/B09SWCJ8FF
I just know that there are some types of motors that have a limited degree range that can rotate through, sorry im still quite new to the hobby
Good! Then there is no need for any Arduino to be involved. A motor and a drum to wind the cord on, some switches to control the motor and a power source is all that is needed.
yea thats a fantastic idea, thank you very much, I know someone above recomended brushed DC motors, do you think they will work for this project?
oh okay awesome! thank you so much for the help and advice its much appreciated!!
You will need a motor that can easily provide the torque and shaft rotation speed that the project requires (best to overestimate required torque by a factor of two).
Tutorial Pololu - Force and torque
Please tell us if you think you are going to just buy what you need or are you able to actually construct it from components?
If you are referring to constructing motors, then no we will have to buy motors as we are not able to make our own motors
we are most likely going to build the structure to whatever the torque we get is, the goal is the biggest structure possible so the higher torque motor we can get, the better
No, of course not. I am referring to the structure that will hold your motor and drum to wind the cord and hold the relays to actually control the power to the motor.