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A new dawn... programmable window blind

Discussion in 'General Electronics Discussion' started by Mat, Jun 30, 2014.

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  1. Mat

    Mat

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    Jun 30, 2014
    Hi,



    Hoping for some advice!



    I work funny hours, including late shifts and nights, and so getting good sleep at random times of the day is really important to me. I also find it beneficial to wake up gradually with natural light. So I have a plan: I want to install a blackout blind, and then fit a motor on a programmable timer that will gradually open the blind just before my wake up time, to create a “dawn” for me to wake to, any time of the day I wish.



    My requirements are as follows:

    1. Complete black out when blind closed

    2. Must be very easy to set the opening time (i.e. no need to boot up a computer) – ideally from android smartphone

    3. Must open very slowly, e.g. over a 30 minute period

    4. Must have an almost silent motor

    5. Must have manual override (that doesn’t take 30 mins to open)

    6. I’m hoping for a total cost <£100

    Plan so far:

    1. Use a standard roller blind with blackout cloth, mounted on the ceiling of the window recess (133cm wide x 209cm high)

    2. Connected to mains power, transformed down to lower voltage if required

    3. High torque, low speed motor, geared down even further. Something out of a tape deck?

    4. Possibly mount motor in box stuffed with modelling clay for silencing effect



    I would really like some advice on possible control systems, and whether the whole idea seems feasible at all! Reading around the web have seen talk of Arduino, PICAXE etc, but my knowledge in this area is limited.

    I can do a bit of programming, wiring, soldering, carpentry etc, but not sure yet if this project is beyond my skills or not!



    (PS I have looked at the Somfy blind motors, but they are expensive, and it doesn’t look like you can make them open slowly enough.)



    Thanks,

    Mat
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Roller blinds can be reasonably noisy, and may also have light leaks around them (depending on how they're fitted, and what to). Getting them to open slowly (and quietly -- oh, and evenly) might be a challenge.

    you also need to deal with the fact that our sensitivity to light is not linear, so (especially if you've been in the dark for some time) the first couple of mm of opening will produce a perceptually larger increase in light level that you get from 10% open to fully open.

    I think the "total blackout" and "quiet" option are going to conflict given your budget. That's where you need to apply the most ingenuity.
     
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Hi Mat and welcome to the Electronics Point forums :)

    Have you considered alternatives to natural light?

    LED technology is advancing all the time in terms of spectral accuracy and efficiency. See the blog at http://edn.com/electronics-blogs/4390303/LED-Zone and the article at http://edn.com/electronics-products/other/4431335/LEDs-offer-almost-natural-sunlight-colour-spectrum. You can easily simulate a sunrise by using a variable dimmer; no mechanical parts required.

    I bought some incandescent "natural light" bulbs. They look like standard incandescent lamps, rated at 100W, with blue-tinted glass. They emit a very bright, yellowish, natural light. These would not produce the same spectrum if dimmed though. This might be an advantage though, because the spectrum of daylight clearly varies during sunrise as well.

    A simple way to control an external device using a smartphone is by playing an audio file through the headphone socket into some custom circuitry. The "sound" can consist of a tone whose pitch (frequency) controls the external quantity. Frequency-to-voltage conversion is not difficult, and the variable voltage could control LED brightness, or a servo controller to move the blinds (if you can overcome the other problems with the mechanical approach).

    I have no experience with this stuff; just throwing out ideas.
     
  4. Gryd3

    Gryd3

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    Jun 25, 2014
    My first thought would be a cheap alarm clock, rip out the buzzer and you have your adjustable alarm already setup with a display.
    Patch in a stepper motor and micro-controller to control the blinds. (Stepper motor would allow fine control over the speed at witch the blinds open)
    If your messing with a microcontroller, you could probably use a phototransistor to help control the rate that light comes in.
    Your MCU could easily have a manual over-ride for open/close as well, and would only trigger the 'dawn' blind opening sequence when the output from the alarm clock drives it.
    Best of luck, I'm curious to see where this goes for you!
    As far as your noise concern... that may be tricky to combat. Go play with some blinds to find a smooth operated blind.
     
  5. Kiwi

    Kiwi

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    Jan 28, 2013
    I think gradually turning on a light as suggested by Kris would be a better idea than trying to raise a blind.
    The bulb would have a constant controllable rise in brilliance, but the amount of light entering when slowly raising a blind will depend on how bright it is outside.
    Arduino have a "Fade" function that might be worth a look.
     
  6. Mat

    Mat

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    Jun 30, 2014
    Thanks all for responses.

    *steve*: yes I had been thinking that the first few cm would have to go much more slowly than the rest. If I used a stepper motor, I could get it to do 1cm in the first 10 minutes, 10cm in the next 10 minutes, and 100cm in the next 10 minutes, for example. In terms of the light leaks you mention, I had been thinking of some kind of frame that the edges of the blind would run in, to minimise this problem.

    KrisBlueNZ: Yeah you are right artificial light would be a much easier solution! Can buy off the shelf alarm clocks that do this for £50 or less. Somehow it doesn't appeal to me as much as building my own and using natural light though... If it seems beyond my skills though it's a good fallback option... Your other point about using a smartphone to play an audio file as a control signal sounds like a good one though. I can just set an alarm with that sound file, and plug it in to a minijack wired to my bedside.

    Gryd3: Alarm clock also good idea, although the smartphone audio file idea would allow me to control the length of the alarm easier perhaps. Stepper motor + microcontroller sounds good, with manual override - any ideas of where to learn more about these? I have little idea of which ones to choose!

    Kiwi: thanks, I will have a read about Arduino fade function.

    Thanks again for your input, and more thoughts much appreciated!

    Mat
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Yes. Also, the sound file would give you complete control over the fade-up. You could use different sound files to give you different fade-up periods, different maximum brightness, or different "shape" to the brightness vs. time graph. That versatility was the reason I suggested it.
     
  8. Gryd3

    Gryd3

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    Jun 25, 2014
    It may require playing around with the smartphone you plan to use.
    My Samsung Galaxy S3, LG Optimus 3D, and Sony Xperia Play will automatically stop playing the alarm after a few minutes. (They all have settings for 'snooze duration' though which would allow you to replay the sound every n-minutes)
    If you test your device and this is of no concern, than it sounds like a good plan of attack.

    Edit: Also, about learning different MicroControllers and Stepper motors can be done on all sorts of sites.
    May people have a favorite flavor of chip, and programming language. Because it seems as though you are very new at this.. take a look at the arduino family. The IDE is really easy to pick up and write with right away without needing to know Assembly language ;)
    There is a very large range of Stepper Motors.. from the little guys you find in a flatbed scanner, to the big beefy ones that provide motion on CNC machinery. They also have different wiring configurations... more on that later. Which one you choose will depend on how fast you want it to go, or how much torque you want. Regardless of your alarm source, I do feel a stepper is the way to go to control your blinds.
    http://arduino.cc/en/Tutorial/HomePage
     
    Last edited: Jul 1, 2014
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    I didn't mean that he would use the normal alarm system on the smartphone. I was thinking that it could be done either using an app that could either send commands to other apps at particular times of day (e.g. start the music player at a certain time) or by adding a long period of silence to the start of the audio file so he would start it playing before he went to sleep. There might be other ways as well.
     
  10. Mat

    Mat

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    Jun 30, 2014
    Some good points about the practicalities of playing a 30min sound file at a specific time, thanks. I'm guessing it must be possible to find an app that will do this, without running into snooze problems.

    I like the idea of avoiding assembly language! Have spent the last couple of hours reading the arduino website, and it looks suitable. I think I will need to buy a board and start messing around with more basic programs to get a feel for the language, then buy a stepper motor "shield", and a stepper motor. Would I also need a "shield" to convert the audio signal into a control voltage? Also, any advice on whether an arduino Uno would be sufficient in terms of connections and memory etc.? I have a feeling I'll only know which one of the dozen Arduinos on offer is the one I need once I have brought one and played around with it...
     
  11. Gryd3

    Gryd3

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    Jun 25, 2014
    Arduino Shields exist to make your life easier and are not a requirement.

    Stepper Motor drivers typically require a 'Step' input and 'Direction' input. A shield is easy in the fact that it's pretty much plug-n-play, but you can use almost any Stepper Motor Controller if you spend a little extra time coding the output of your MCU.
    Audio input for your Arduino will be pretty easy. You are not recording the audio or processing it... you should only focus on the frequency (or amplitude... but this is much harder to calibrate). Take a gander there are plenty of resources on frequency counting.

    ---- Alternative Method ----
    Of course you could ditch the Microcontroller (I like them for prototyping and development because I change my mind a lot and it seems much easier to change the circuit behavior.)
    Generate a square wave audio file and feed it to the 'step' input on the Stepper Controller.
    You could either use a simple switch to dictate direction, or control direction with a second audio channel (Left / Right). Your manual override would simply be a multivibrator or 555 timer that would get patched into the 'step' input of the stepper controller.
    *You will need to make support circuitry for your audio side of the circuit to condition the signal properly.
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    If you're going to use an Arduino, you can probably ditch the idea of using a smartphone with an audio file to control things. You might as well do it all on the Arduino. You can get a real-time clock shield, I think, and a display to allow you to program in dates and times. Getting the Arduino to do everything gives you the maximum flexibility.

    The Arduino Uno appears to have 32K of Flash ROM for the program and 2K of RAM for data. That should be plenty.

    Just to be clear, you don't need any control voltage or audio circuitry. The Arduino needs to know the current date and time (hence the real-time clock) and it needs to be able to control the stepper motor to gradually open the blinds at the right time.
     
  13. Gryd3

    Gryd3

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    Good call on the RTC shield... I am not as familiar as I could be with the available shields, which I why I had recommended tapping into small battery operated alarm clock ;)
     
  14. Mat

    Mat

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    Jun 30, 2014
    Hmm I take your point. Although won't it be much more fiddly to set an alarm time via some interface on an arduino than on a smartphone? Would I need a keypad strapped to the side?

    I think I will just buy an arduino starter kit and learn how to use it, and then decide on a firm plan once I have seen how much complexity I can cope with!
     
  15. Gryd3

    Gryd3

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    Jun 25, 2014
    Two different approaches.
    Setting the time on a SmartPhone will probably feel more polished and futuristic ;)
    ... but you will either need to source a program that will do what you want, or write your own.

    Setting the time on the Arduino should not be any more finicky than setting the time on a bedside clock or kitchen timer. You are the architect. Give it enough buttons to set the time smoothly and comfortably. The LCD that you attach to it will show you anything you can code it to.

    Ultimately, there are many approaches, and the one you choose should be based on desires and experience.
    For ease of looking at your project, split it into two parts:
    Clock/Alarm and Blind Controller.

    Your clock/alarm could be:
    A Smartphone - Require finding or writing an app to control an external device.
    * Possibly the cleanest, most modern UI. (Ease of changing the opening rate by creating a WAV file)
    A MicroController (Arduino, PIC, etc) - Require writing your own program.
    * Can integrate both parts of your project together for a single solution.
    External Alarm clock / Pre-made circuit - Require modification to tap into or condition the output to drive your Blind Controller.
    * Probably the easiest to use, but could very well result in the least 'polished' product.

    Your Blind Controller could be:
    A MicroController - Require writing your own program.
    * Easier to add / change features and control parameters to function as desired.
    Discrete components - Require a greater deal of work in constructing the circuit.
    * Harder to add / change features, but could result in more cost effective solution.

    (I would recommend that both Blind controllers use a pre-made stepper motor controller... either a shield, or any other stepper controller. They usually have built in features that will increase the reliability and function of the stepper motor over a simple home-made one.)
     
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