I’m looking at getting this step motor to lift a weight via a pulley. The string would be directly attached to the step motor shaft, as it spins the string will wrap around the shaft or be unwound from the shaft based on the direction the motor is spinning. I’m completely lost at where to begin, I’m a programmer and not familiar with motors or driving them.
I’m thinking from what I’ve read I need a step motor with a worm gear to allow the motor to hold the load when not operating.
I know many people get into the debate of calculating the needed force, I’m not interested in that. I just need a solution to control a motor via the Arduino. The weight would be around 10 lbs.
Attached is a simple diagram of what I’m looking to do. It really is hard to find a simple “this is what you need & here is how you wire it” solution online.
I was looking at using the step motor so I could keep the weight balanced between two points. Kind of like lower the weight 500 steps, wait a few seconds, raise the weight 500 steps..... and so on back and forth.
You could make a simple optical sensor to count revolutions of DC motor or (better) of the shaft that winds the string.
The QRE1113 is very cheap and can easily detect a blob of white paint on a rotating black surface. Sparkfun sell them on a breakout board - use the version they call analog. But it is easy to use the “raw” IC also.
I know many people get into the debate of calculating the needed force, I'm not interested in that. I just need a solution to control a motor via the Arduino. The weight would be around 10 lbs.
Alas nature isn't interested in random guesswork, so you may blunder about pointlessly with a setup
that can never work (or one that's 100 times over-engineered) unless you at least have a basic back-of-the-envelope
awareness of the needed torque. Its one simple equation, torque = force x radius.
I'm working to build something similar but my max weight is 15lbs.
I am using a 6:1 pulley system (two triples) to reduce the load factor to about 3lbs.
For my project I am using the 42STH38 NEMA-17 Bipolar Stepper with 26.85:1 Gearbox stepper from http://www.phidgets.com/ it has has an 8mm shaft. I've coupled the shaft to an interface plate made for the Nema-17 to a 6" v-pulley as the main draw-up and draw-down using 2.5mm spectra line (800lb grade).
Given your weight requirements I'd go for a 1067_0 - PhidgetStepper Bipolar HC motor controller and something in the realm of a 3328_0 - 42STH38 NEMA-17 Bipolar Stepper with 51:1 Gearbox from phidgets
To me the key was using the 6:1 pulley to reduce the load on the stepper.
In regards to the adruino and other micro steppers....I'll let the experts on this blog guide you...I'm having a nightmare working on the micro level vs macro....but I'm also trying to learn and minimize my power requirements....
a 6" pully with a 10lb weight? That’s a lot of torque, but yea, I think it should be doable. You might want to consider this driver instead:
I’ve used the DRV8825, and it does work well with <2A motors, and you can drive it at rather high voltages, which is going to be something you’re going to need, given that you need about 10,000 steps per revolution (200 S/R * 50). You should be able to use the same heatsink on the pololu, or you might check to see if pololu has a heat sink available. There’s also a chinese made DVR8825 clone of the pololu board that are available I think it’s 5 for $10 on amazon and comes with the heatsinks.
I think that set of block and tackle you’re going to use is probably bigger than you think it is. Probably quite a bit larger than you think it is.
Either way, I think you got most of what you need there.
You'd imagine a place called "robotshop" would know a 1.7A NEMA17 stepper doesn't have a voltage rating
MarkT, here is a note listed on the product description from the robotshop website. They understand the voltage, but are simply giving a recommendation.
Note: The 2.8V refers to the phase voltage which is different than the 12V rating we give it. At the end of the day, stepper motors don't have a "Rated Voltage" per se. You can run them at a wide range of different voltages and it will just change the performance of the motor. We recommend that you use this motor at a minimum of 12V but you could run it at 24, or 30 if you wanted to and the motor would simply perform a bit better (require less current for a given speed and torque).