Would this automatic curtains / blinds controller design work? Answered
I have been searching for ways to make an easy and cheap automatic curtains/blinds controller but have not really seen any that actually meets my basic needs but also does not require lots of complex IC components. Please let me know of any instructables I may have missed.
So here is my design - hoping everyone can help to validate it and discuss design faults and improvements (mainly to reduce costs).
1) Costs: Total costs should be around $20 per curtain. I think professional systems cost about $100-$200 per curtain controller.
2) Parts: Easy to build and put together with some soldering. Parts are easy to find/buy or substitute for similar components.
3) Function: At least 2 buttons. One UP button and one DOWN button for manual triggering (wireless buttons would be better).
4) Function: One press of Button A fully opens the blinds with the motor stopping at the correct place to avoid damage to the blinds or the motor. The opposite goes for Button B to close the blinds.
5) Function: The controller should never be able to open or close the blinds past the normal safe positions, causing damage.
6) Optional Parts: Complete system is small enough to fit inside the blinds/curtain's cover / awning. I think it should be easy to fit in most covers anyway.
Briefly how it should all work:
With the curtains rolled up, you would press button A, which would roll the curtains DOWN, then stopping at the correct place (covering the whole window). Pressing button A once again would not do anything or further roll DOWN the curtains.
Then, press button B and the curtains should start rolling UP constantly, stopping just before it gets to the top. Pressing button B once again would not do anything or further roll UP the curtains, avoiding damage to curtains or motor.
Design/diagram below (sorry for the poor details, i used MS-Visio to draw it out).
The Parts/Components (under $30 at time or writing):
1) 5-10kg servo $7 (using 5volts) that can be power in forward or reverse spin. Slow spinning speeds would be best for safe and low power operation?
2) Some hand made adapter to firmly connect the servo motor shaft to the curtain's shaft to spin/roll the curtains ($0 free).
3) A wireless power relay $14, (12 volts) with 2 channels and "constant on power" functions (links below). I guess wired relays are fine, but I would want to hide the wires to the buttons.
4) 2x 5V regulators $2, to reduce the 12v power from the Relay to 5v for the Servo.
5) 2x Magnetic or reed switches $5 (12 volts) that is Normally On (normally connected).
6) 4x Rare earth magnets $1 to work with the reed switches. These are small, thin and easy to hide, but are very strong.
7) A power source for the relay, 4x 18650 batteries?. Should be 12 volts or depending on what relay & servo combo you use. (links below)
1) Make an adapter to connect the servo to the blind's shaft. I dont have a picture of one or the steps for this as every servo & curtain combo situation will be different, but im sure it should be simple to make. Fail or malfunction of this part would cause too much damage to anything really?
2) For best practice, use temporary wiring to connect all the components together as per diagram and test out the functions as if they were installed in their places and on the blinds.
3) Glue or connect the adapter, curtain shaft and servo shaft together. Also mount the servo firmly somewhere, on the wall or curtain cover so it doesnt end up spinning itself.
4) Position both magnetic switches on the wall, behind and just under the curtain's roll of fabric as per diagram. A lot of testing and playing around will be needed to create the correct gap between each switch and curtain. Switch A (Limiter A) will be the most difficult to position. It will be used to stop the servo from rolling the blinds too far down. This means the magnet glued on the blinds is up high on top, which will be rolled inside layers of fabric and may spin close to Limiter A multiple times which may cut the circuit/power earlier than intended as the magnet spins round and round. Limiter B should be easier.
5) Wire the 2 channels on the relay to the Servo and the Limiters. The 5V regulators goes between both channels of the Relay's power OUT and the Servo's two power Inputs. Screw or glue the relay to somewhere firm like inside the curtain covers.
6) Glue the rare earth magnets to the desired positions, or sew them on if you dont trust the glue. The magnets will physically cut the power to the servo by activating the Magnetic reed switches, so using 2 magnets would be even better, just incase the servo you use spins really fast or has a lag.
7) Connect the relay to the battery/power cable. Of course double check all is good before adding power. In my case, I will have 12v power cables available to use.
8) Put the curtain cover back on to hide everything. Hopefully you did not create creases in the curtain fabric where the magnets are glued. Oh and maybe remove the curtain draw strings (used to pull up & down the curtains) to avoid breaking the Servo?
Detailed explanation of how it should work:
- The blinds are fully rolled up.
- Press Button A once, Relay provides power to Channel A, Servo spins clockwise constantly (rolling down the curtain).
- Servo's positive line A is cut (circuit open) when Magnet A rolls out and comes close to Limiter A. Relay is still outputting power to Channel A but no power goes to the Servo.
- Press Button A once again, the Servo should not do anything. The Relay should then stop outputting power to Channel A.
- Further presses of Button A does nothing but toggles Channel A's power on and off. Magnet A & Limiter A still disabling power to the Servo.
- Press Button B once, Relay provides power to Channel B, Servo spins anti-clockwise constantly (rolling UP the curtain).
- Servo's positive line B is cut when Magnet B rolls up close to Limiter B. Relay is still outputting power to Channel B.
- Press Button B once again, the Servo should not do anything.
- With this "latch" functionality of the Relay (see link below and product details), it is also possible to stop the curtains mid way, which might be useful for some people, i dont think i will use it.
For future upgrades:
I think it would be possible to control this controller from a PC program, by directly connecting IO cables to the Relay's button A & B on the PCB. Sending pulses from the PC as though it were remote button presses. Or just bring the remote to the PC's IO ports and connect there. Would anyone disagree?
- An example Servo: http://www.ebay.com.au/sch/i.html?_nkw=High+torque+Metal+Gear+RC+Servo
- The wireless Relay: http://www.ebay.com.au/sch/i.html?rt=nc&LH_PrefLoc=2&_nkw=2CH%2012V%20Wireless%20Relay
- The 5v Regulators (L7805): http://www.ebay.com.au/sch/i.html?rt=nc&LH_PrefLoc=2&_nkw=5v%20regulators&_fln=1&_trksid=p3286.c0.m283
- The magnetic reed switches: http://www.ebay.com.au/sch/i.html?_nkw=reed+switch
- The rare earth magnets: http://www.ebay.com.au/sch/i.html?_nkw=rare+earth+magnets+n38
- Design/diagram: http://i50.tinypic.com/118emas.jpg