Hey guys! Doing a DIY “Smart Blinds” project, and i’ve done som calculations on my blind (This type: https://goo.gl/BzoXj5).
It measures W:174cm x H:240cm. Used a travel weight to measure the pull-force and that seems to be around 1,7kg. Tried some times and would round up to 2kg.
Now I need to figure which stepper motor I need to be able to lift these blinds. There is no need for any “holding torque” as I understand, because the beads-type string is holding the blind.
What stepper motor (Needs to be a stepper motor, so it ‘knows where it is’.) should I get?
Requirements:
Continuous rotation
Cheap
Small
I’m looking into gears also, because it’s a lot of weight to pull for a small motor. Though when looking for NEMA 14/17 motors, they are very expensive. Any ideas?
Hi Tom! Thanks for the answer.
It gave me a lot of of researching to do, which was really great. I thought stepper motors would be the perfect fit, but I actually think this is much better, and cheaper.
You need to know how fast you want your blinds to raise or lower.
For example, that motor has a shaft diameter of 6mm. So the circumference of the shaft = 6 x pi = about 19mm.
If you were winding your blinds’ pull cord on this shaft, in one minute it does 30 revolutions = 19 x 30 = 565mm.
i.e. it would take one minute to raise the blinds half a meter. So you you might want a faster motor.
However there are other things to consider, is the pull cord to blind height raise/lower 1:1 or is it geared? Are you really going to wind on the motor shaft or on a pulley of larger diameter?
Just as in my calculations above, converting the diameter of your pulley to circumference and multiplying this by the rpm gives you linear movement of the motor per minute. Then dividing by the pull cord to blind movement ratio will give you linear movement of your blind per minute.
Try a few of the motor speed options. You probably dont want your blind to whip up super fast, I reckon somewhere around 3 meters a minute would be good.