Window Chain Actuator

thingiverse

UPDATED 2019-11-07 (update notes at the bottom) I made myself a window chain actuator to automatically control room temperature in winter. Actuator uses 28byj-48 12V stepper + ULN2003, Arduino Uno, DHT22 temperature sensor and 16x2 LCD. Everything is powered with 12v 2A power supply. Design works nice and without issues already for a half a year. I just set desired room temp, 22°C in my case, and if room temp drops or rises over 22±0.1°C actuator starts slowly close or open window until temp goes back to 22±0.1°C. 12V stepper motor version isn't wide spread, but it is mandatory since 5V version is too weak. Only now I redesigned some parts to fix some things for easier pinting and assembly. But I didn't printed new design, so bear in mind. If something wrong goes please let me know, I will try to fix design or give some advice. Video how it works and photo of it mounted on the window at the bottom. It's sad I didn't took time lapse of how it moves window... Maybe next time. Before you start, I want to warn that you need M3 Tap to create threads in plastic. This is because I don't want to waste plastic for trial and error finding right size holes. Other thing you need is 2.4mm TIG welding wire to make pins for sprockets and rollers. Some photos have explanation notes. Chain can be printed whole at 0.2mm. There is 0.2mm gab between segments so it should not fuse. To break segments loose use big flat screw driver. Chain segments need to move very easily, so it probobly will need some post processing. Or you could try setting extrusion width to 0.4mm instead of 0.45 on perimeters and infill. To connect chain segments I used PETG 1.75mm filament. Note that some parts have specified side to them and are marked with "R, L, +, -". Parts named with "right" goes to "R" side, "left" to "L", "+" to "+" and "-" to "-". Keep in mind that "+" and "-" have to align or face each other. Most of the parts are printed with PLA at 0.2mm height. Only Sprockets and Worm Shafts at 0.1mm. Parts to print with supports: Base - Support on build plate only. There is modeled-in support at front, after printing break it off. Big Sprocket Left/Right - Support on build plate only. Print at 0.1mm height setting (very steep angle). Roller Spring - Everywhere. 2pcs. Rollers Hodor Left/Right - Support on build plate only, but should print without support. Small Sprocket - Support on build plate only. 2pcs. Print at 0.1mm height setting (very steep angle). Some parts need two or more copies printed: Big Roller x2 Roller Spring x2 Small Roller x6 Small Sprocket x2 Pins: 2.4x12mm 8pcs for rollers and small sprockets. 2.4x9mm 2pcs for roller springs. 2.4x28mm 2pcs for big sprockets/gears. 2.4x10.6mm 1pcs for window frame hodor. Screws: M3x8mm Hex Socket Countersunk 9pcs M3x16mm Hex Socket Countersunk 3pcs for "Latch" M3x8mm Hex Socket Botton Head Cap 12pcs M3x12mm Hex Socket Botton Head Cap 2pcs for center holder not to protrude into shafts. Because of chain friction to Base we need some sort of help to move ends of chain. For that we can use fishing braid or capron thread. Thin will suffice, no need for thick one. I use regular sewing thread not even capron and it holds. We also need to lube Worm shafts with PTFE White Grease. Lube places where it contacts plastic. It eases stepper job and removes rattles making actuator silent. Do note that stepper itself makes noise, to reduce it I used my own code for Arduino. Dunno what other libraries do to introduce so much noise. A bit about fixing actuator to window frame. Originally I only fixed it with "Window frame hodor" (sorry about stupid naming scheme). It still hold up, but from start I had some horizontal alignment issues because the stepper motor side is heavier. In new design I added left and right side holders to solve it. At first I recommend to fix "window frame hodor" to window frame. Attach left and right holders to actuator. Put actuator on center holder which should already be fixed to window frame. Align actuator and fix left and right holders to window frame. After that attach center holder to actuator, it should be easier to attach it now. With original design it consumed a lot of my nerve cells to attach it :D You can print bigger "Bearing" to support chain if whole actuator sags too much. Or print smaller if chain doesn't move freely. My design is different in this area so it's trial and error for you. I just hope I designed right one from first time :) STEP files included. Tired of writing, if I will remember something I forgot to write down I will make update at the bottom with time stamps. Good Luck! UPDATE 2019-04-26: added redesigned chain for easier print "Chain Whole V3" and fixed bug, both sides needs equal number of chain parts, old design has one missing chain part. Old design for some people fused too much, couldn't get it separated. Just break off orange parts. New design needs very little to no post processing. Explanation could be found in photo. Just remember, while connecting chain parts, filament should go easily through top and bottom holes, but should not be too loose, otherwise whole chain in the end will flex too much. Center hole has smaller diameter, it should be tight to hold filament from falling out. For nice and flush look I cut filament on top and bottom with blade cutter. Looks way better than using snipping pliers. UPDATE 2019-08-16: added schematics and code. For "Opened" and "Closed" switches use Snap-Action Switch. I use switches like these https://www.pololu.com/product/1403 but bought in local electronics shop. Connect switch side pins, middle pin not connected, otherwise you need to change code. Link to code: https://pastebin.com/6gYq1ZfD Libraries needed to install for code to work: https://github.com/dxinteractive/AnalogMultiButton can be found inArduino IDEs Library Manager https://github.com/olewolf/DHT_nonblocking not in Library Manager. In code line 13 you need to change values otherwise button press will not be detected. To get values you need after assembling electronics you have to upload short code to Arduino https://pastebin.com/r0Lqv9Z4 After upload open serial monitor, set baud rate to 9600. Press button, write down value, press next button, write down value, do it for all 5 buttons. In my case buttons are positioned like that: Open, Minus, Default, Plus, Close. Plus/Minus changes set temp, default resets set temp to default value of 22 celsius. Open/Close sets motor full speed and opens/closes window. Video at the page bottom is only to show how LCD looks like. It uses same code but window opening mechanism is different so bear in mind, look to the upper left corner. UPDATE 2019-11-07: added missing files for Steper Shaft and Helical Gear Right.