Hi, so my end goal is to make an automated riser blind with a stepper motor but I have no idea where to start figuring out what stepper motor I need to buy. I am an absolute beginner in motors and stuff so anything to get me pointed in the right direction would be appreciated.
The blinds weight is about 3ish lbs.
This depends on the speed that your blind shall be moved up / down.
If this stepper-motor is driving a high-ratio-gear which translates the rpm to a slow value the steppermotor could be quite small.
You win torque at the cost of speed
3lbs is aproxx 1,4 kg. It also depends on the diameter that you use to roll-up the blind.
Can you post a picture of how your blind is looking like?
best regards Stefan
We have the same problem, without knowing the torque required to move the blind and the speed you need to move the blind we cannot give you a valid answer. If it were me I would use a BLDC with a gear box. Also what is powering this thing?
With a wormgear motor like this
https://de.aliexpress.com/item/4001068594973.html?spm=a2g0o.productlist.main.7.6e111e601R1zg7&algo_pvid=0f0a5c1b-7366-4151-9010-33f484434d5c&algo_exp_id=0f0a5c1b-7366-4151-9010-33f484434d5c-3&pdp_npi=4%40dis!EUR!7.80!6.24!!!8.28!!%40211b88ef16934206145077399edaa2!10000014021591100!sea!DE!812311978!&curPageLogUid=vweH4bpgE4Me
If you take a version with very slow rpm 5 to 6 rpm this motor has a lot of torque.
This kind of motor has a encoder that sends pulses while the motor is rotating.
Your microcontroller can count these pulses to determine the position of the blind.
regardless of using a stepper-motor or such a DC-wormgear-motor
you need minimum one sensor to determine a position like blind fully up or full down.
Depending on the design of your blind it might be easier to simply use two sensors that - if one sensor changes his signal stop the motor.
And then you could use a normal DC-gear-motor without encoder.
So please post a picture of your blind and write what functions do you want to have with the blind
simply up/down until end-position or something else?
best regards Stefan
My main problem was that I had no idea how to calculate the torque required so that's why I am asking. I should have said that in the first post.
So for me, speed isn't super important, if they can go up or down within a minute then that is fine. My idea was that I would have them rotate a calibrated amount of steps before stopping when going up or down and that was it, so pretty simple. I'm basically trying to copy the ikea blinds but much cheaper. FYRTUR Black-out roller blind, smart wireless/battery operated gray, 32x76 ¾" - IKEA
Will you build the whole mechanic yourself?
or
will you mount a motor to an existing mechanic?
let's estimate your blind is 200 cm long.
let's estimate the diameter of the wind-up is 4 cm.
this means the circumference is 4 cm * 3.14 = 12.56 cm
For winding up 200 cm in 1 minute means
200 cm / 12.56 cm = 16 rpm
The 6V motor with 15 rpm has a torque of 2.6 kgf.cm which is 0.25 Nm.
If your blind has a weight of 1.4 kg and hangs down on a wind-up with diameter 4 cm this is a radius of 2 cm.
Weight-force of 1.4 kg: 1.4 kg * 9,81 m/sec² = 13.74 N
F = 13.74 N
torque is
torque = F * l
torque = 13.74 N * 0.02 m = 0.275 Nm. Which is slightly more than what the 6V motor with 15 rpm can do. (0.25 Nm)
Or you use a 12V motor at 18 rpm which has a torque of 4.5 kgf.cm = 0.44 Nm
This is the calculation.
As you can see:
bigger wind-up-diameter faster winding-up per rpm but more torque required
or vice versa
smaller windup-diameter slower winding-up per rpm but less torque required.
You will make to have some design-decisions and then choose a motor
or choose a motor and then design your mechanic in a way that the motor can deal with it.
The numbers (tables) are taken from this worm-gear-motor
https://de.aliexpress.com/item/1005005957359255.html?spm=a2g0o.productlist.main.3.6e111e601R1zg7&algo_pvid=0f0a5c1b-7366-4151-9010-33f484434d5c&algo_exp_id=0f0a5c1b-7366-4151-9010-33f484434d5c-1&pdp_npi=4%40dis!EUR!14.70!13.23!!!15.60!!%40211b88ef16934206145077399edaa2!12000035040099400!sea!DE!812311978!&curPageLogUid=khkhBqXzY168
If you still want to use a stepper-motor now you know how to calculate it.
You should consider the following thing:
a stepper-motor must be under current all the time to keep the position.
If you use a worm-gear. The worm-gear will be self-locking.
With a stepper-motor you need at least one reference sensor
With a DC-motor you need two sensors for the endpositions fully up / fully down
best regards Stefan
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Awesome, thanks for the help, I'll look into worm-gears.
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Hi Purerandom,
Where you able to achieve what you were looking to do ?
Did you finally make use of Stepper motor and how did you make use of reference sensors ?
Thanks
Watersoup
a steppermotor will require to keep the motor power 24 hours per day 7 days per week = all the time
Except you use a self-locking wormgear.
You can use a stepper-motor but a stepper-motor with suffcient torque will be bigger in his size as a dc-motor
And DC_motors are avaialbe with encoders. example is this one
https://de.aliexpress.com/item/4001068594973.html
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