Trying to use a NEMA 17 setup and I have the 5mm Shaft of the motor connected to a 6mm shaft of one of the telescope's axes using a standard coupler. when turned on the motor just vibrates and is incapable of turning the shaft, sometimes i can wiggle the motor to "catch" at a certain angle and it will work for a second, most likely until it encounters a position that requires more strength to turn. I'm guessing the NEMA 17 doesn't have enough direct torque to turn these shafts with just a coupler setup? I'm fairly new to all this and any help would be appreciated, even if its just "use this other motor", "here's how to figure out how much torque you need on your telescope shaft". Thanks in advance.
Also, the code and assembly to the Arduino is all solid if i don't have the motor connected to the coupling it works just fine on its own, and im trying to turn the motor as slow as possible to be able to handle more torque.
There are hundreds of different Nema17 motors. Nema17 just tells you that the front face is 1.7inches across. Post a link to the datasheet for your motor and tell us what stepper motor driver you are using and tell us what motor power supply you are using (volts and amps) and post your program.
Stepper datasheets have two pieces of torque information. The "pull-out" torque indicates the torque that will cause a stationary stepper to be forced out of step. Ignore that, its seldom any use to anyone.
The other key data is the graph or graphs of dynamic torque against speed (usually provided for several different
driver supply voltages). This is the real deal - note torque drops dramatically with speed with all steppers, and higher supply voltages help. Dynamic torque is a lot lower than pull-out torque, this catches a lot of people out.
The other issue with steppers is resonance - this, if undamped, will severely undermine the performance of a stepper used with full-steps. Always use microsteps for maximum smoothness and reduced susceptibility to miss-steps. x8 to x16 is a good starting point (too high and its harder to generate enough step pulses...).
MarkT:
Stepper datasheets have two pieces of torque information. The "pull-out" torque indicates the torque that will cause a stationary stepper to be forced out of step. Ignore that, its seldom any use to anyone.
The other key data is the graph or graphs of dynamic torque against speed (usually provided for several different
driver supply voltages). This is the real deal - note torque drops dramatically with speed with all steppers, and higher supply voltages help. Dynamic torque is a lot lower than pull-out torque, this catches a lot of people out.
The other issue with steppers is resonance - this, if undamped, will severely undermine the performance of a stepper used with full-steps. Always use microsteps for maximum smoothness and reduced susceptibility to miss-steps. x8 to x16 is a good starting point (too high and its harder to generate enough step pulses...).
This is very helpful information Thank you. Is there a way to determine from the shaft on the telescope mount how much torque I should be looking for?
Robin2:
There are hundreds of different Nema17 motors. Nema17 just tells you that the front face is 1.7inches across. Post a link to the datasheet for your motor and tell us what stepper motor driver you are using and tell us what motor power supply you are using (volts and amps) and post your program.
Here is the driver Im currently using its a TB6612, the Schematic I've setup is also on this page:
Again though I think my problem is the torque required for the shaft on the EQ Mount of the telescope and I'm just too green to figure out how to know what torque would be needed on it from just the turn of the shaft itself.
Also to note im using 12v power supply to the Arduino
Scarpa:
I'm just too green to figure out how to know what torque would be needed on it from just the turn of the shaft itself.
There is a suggestion for a simple way to measure torque in the link I gave you.
I don't think the TB6612 is a specialized stepper driver. A better choice would be a DRV8825 as it can limit the current to protect the motor thus allowing you to use a higher voltage for the motor for better performance. The Pololu DRV8825 web page has lots of useful info.
Scarpa:
This is very helpful information Thank you. Is there a way to determine from the shaft on the telescope mount how much torque I should be looking for?
