Please advise on exterior window blinds motor - Page 1
Forum section: electronics / beginners

author: elcrni
author_rank: Regular Contributor
timestamp: May 02, 2023, 07:53:39 pm
content: hi all,So i have exterior window blinds, heavy ones, some 3m wide and they cover glass wall of the room. They are now hand operated via metal crank and i would like to motorize them.I was thinking of using arduino/ESP32 and motor controller board, would also like to add IR remote support as well as mobile support for operating the blinds. I am proficient enough with MCUs and controlling the motor should not be a problem, but have no idea what kind of motor would be the best.So far i made a test rig with NEMA17 stepper, controlled by ESP32 and TMC2209 driver, way way underpowered even when geared to different ratios to operate the blinds but at least i have a working prototype of sort.Should i keep trying larger and more powerful steppers or using a stepper of any size for this is not a good idea?Motor and electronics would be mounted inside and would basically just connect to the hand crank.Many thanks in advance,Alek

author: Infraviolet
author_rank: Super Contributor
timestamp: May 02, 2023, 08:19:52 pm
content: 3D printing some planetary gearboxes might help? You can get pretty decent efficiencies from 3d printed planetary arrangements so long as you're ok with some backlash and don't have huge torque loads at the eventual output. You can get a 6 to 1 torque improvement (speed reduction) ratio in a 3 planet design, and stack two of these in sequence for 36 fold... This means you wouldn;t need such a high torque motor in the first place.You could use steppers, or you could use DC motors with gear box heads on them. With the DC motor you'd need an encoder and/or endstop switches. With a stepper endstops would be a wise idea too, just to ensure it won't damage itself trying to over-travel if it were to loose count of steps, especially duing a reversal of direction. Either can give fairly decent torques.For DC motors the 12Volt 37mm diameter design is quite common, and with large internal gear ratios and slow output RPM you are already looking at easily 5kg*cm of torque from this shaft before entering your later gearbox stages.For steppers NEMA 17 sizes often give torques in he 1kg*cm to 5kg*cm range, although are usually advertised with this rating in N*m.P.S. to be clear, the handcrank is already indoors and has its own shaft arrangment going through the wall to provide motion to the blinds?

author: elcrni
author_rank: Regular Contributor
timestamp: May 02, 2023, 08:37:40 pm
content: Thanks @Infraviolet!I have printed various combinations of gear ratios but not in planetary arrangement.QuoteInteresting...I would pretty much prefer steppers as with TMC2209 i have a stallguard option which would eliminate the need of limit switches, less wires and mess.I am using this stepper for test: Stepperonline Nema 17 Stepper motor 59NcmQuoteYes, handcrank is already there, at the end of it i have an option for different connections so i have printed nice connector to connect to my motor output shaft.I have a lot of experience with 3D printers, steppers and control of the steppers, all my printers use TMC2209 drivers but never before used TMC2209 with ESP32, in general seems to me that this motor is underpowered and weak in this rig.Just purchased some planetary gearboxes from STepperonline, 5:1 and 50:1, just to test and see if i get enough torque.Many thanks!Alek

author: themadhippy
author_rank: Super Contributor
timestamp: May 02, 2023, 09:28:17 pm
content: id measure the force needed to hand crank the blinds first,dont need anything fancy,set of luggage scales would do nicely,or hang known weights of the handle.

author: tooki
author_rank: Super Contributor
timestamp: May 03, 2023, 12:27:27 pm
content: Given that you can buy purpose-made blinds motors (Rollladenmotor) on ELV.de for €120, which go inside the blinds, I doubt building the mechanical part can be done better. You could still use your own controls.

author: elcrni
author_rank: Regular Contributor
timestamp: May 03, 2023, 01:26:43 pm
content: Quote from: tooki on May 03, 2023, 12:27:27 pmThats why i asked the question :-)I see there are quite a few models, i have no idea which one i would need.Also, i guess these mount INSIDE the roller mechanism which to be honest i dont even think i can access as everything is hidden under exterior wall panels that are not removable.What about the roller width as mine are 3m each? do i just install 600mm tube motor or i need a full width motor (that would be crazy but have to ask :-) )?What about limit switches/endstops? i assume i would need to install those as well?I have 6 of these blinds on my home so not just one off.Many thanks,Alek

author: tooki
author_rank: Super Contributor
timestamp: May 04, 2023, 12:04:34 pm
content: I don’t know the answers to those questions. (Not yet, at least: my mom has asked me to look into that for her home, now that she has a shoulder injury and has trouble operating them.)But what’s stopping you from contacting ELV or a blinds installer to find out? If you Google “rollladenmotor nachrüsten” you’ll find tons of companies offering such services, and I’m sure they could answer that.