School project help

Hello people.
Me and a friend have gotten a school project, and we chose to use the Arduino as a foundation for the project.
So i would like to know if the following is possible, and if it is, then i would like some suggestions as what devices / parts to use.

Our main goal is to have 2 motors attached to a window blind (Those who can rotate, and go sideways). When the sun sets directly on the "Window" the blind will shut, so we need some sort of foto cell aswell.

Now, some of the problems we don't know how to handle ourselves is getting the motors to go both ways(Else the blind will be stuck in one side of course).

I would really like getting some suggestions, as for what motor, foto cell if you have anything you can recommend.
Hope you can help us :slight_smile:

Assuming you've done these basic tutorials, have a look at this one which explains how to read a light dependent resistor, and this one which covers motors, including direction.

You'll also need to think about limit switches to switch the motors off at the end of their travel... one of those basic tutorials explains how to read a switch.

Then you'll need to ponder how to get all of that hung together....

Thanks for those links. We have gone through the basics, it's not our first project with the Arduino, but this is a bit more complex than the previous :slight_smile:

Do you have any recommendations as of to what motor and such?
(To elaborate on the motors: They will have to pull strings from the blind, like a loop going around a wheel, that the motor will turn)

I can't recommend a motor because I have no idea how much torque you are going to need. These are vertical blinds? The kind that twist open, but also can slide side to side? Twisting them open will probably not require a lot of torque and you could connect the motor directly to it. The sliding open part will probably require quite a bit of torque. In both cases, it is going to need to be a geared motor.

I do have a suggestion on the cord/pulley motor. I would put strong expansion springs in line with the cord to protect things. If something goes wrong and the motor pulls too hard, the springs will give some room for error and keep the cords from braking.

A wiper motor or power window motor meant for a car will provide a lot of torque. Possibly much more than you need.

To start look at these:
http://www.allelectronics.com/make-a-store/item/DCM-702/3-12-VDC-GEAR-MOTOR/1.html
that one will probably be more than enough for the twisting.
http://www.allelectronics.com/make-a-store/item/DCM-572/12-VDC-AUTO-WINDOW-LIFT-MOTOR-RIGHT-HAND/1.html
This one will likely provide more torque than you need for the cord/pulley. You will need to make or find a large pulley to go along with it. If the blinds are like I am thinking, you will need two pulleys. One unwinds while the other winds.
If you can get into the blinds directly, you could just interface to them directly instead of doing the cords.

If the goal is to only trigger on direct sunlight, you will need some way of filtering out in-direct light. Some ideas that may work are to to filter for infrared. Indirect light will be low in this, but direct light would be high. Another idea is to use black tape and measure the temperature since the black will absorp the light and heat up a little. Using a solar cell and measuring the voltage might also work. A set of polarizing filters in front of your sensor aligned to only pass light when directly in front of it may help as well.

Obviously all of these methods will sense light, but the point is to get some significant difference between indirect light and direct light so that you know when the sun is directly on the window. Some of the options you have may saturate even at indirect light and you will not get a difference when in direct light. Hopefully that makes sense.

Last thought is to think about what happens when the sun is in front of the window. If you watch a wall at some distance, you will notice the angle of the brightest light change. A sundial works on this principle. A sundial will cast a shadow based on the direction of light. So perhaps some arrangement that sensed where the shadow falls would give you enough feedback to know when the light is falling on the window. The bonus to this is you will also know which angle it is coming in at, and could twist your blinds in the proper direction to shield the light. I guess it depends on how complex you wish to make it.

Hi,
Take a look at info on the http://ArduinoInfo.Info WIKI

Motor stuff here: [ http://arduino-info.wikispaces.com/TUTORIALS](http:// http://arduino-info.wikispaces.com/TUTORIALS)

But, a much simpler way is to use "continuous rotation servos". These look like a regular Radio Control servo, but will run continuously and you can control the direction and speed easily. They have built-in motor driving electronics so you don't need to do that part. Since your application probably doesn't need much power, these should work. Example: http://yourduino.com/sunshop2/index.php?l=product_detail&p=129

Simple PhotoResistor should be fine for a photo sensor. Like these http://yourduino.com/sunshop2/index.php?l=product_detail&p=307 Or get a light sensor on a small PC board (An "Electronic Brick") like this: http://yourduino.com/sunshop2/index.php?l=product_detail&p=267 The "Sundial" idea above is excellent. I helped someone make an active sun tracker with two of the simple photoresistors and a vertical blade. If you can orient something like that properly you can tell where the light is coming from and how bright it is.

DISCLAIMER: Mentioned stuff from my own shop... but you can get this stuff from Sparkfun or Adafruit etc.

Thank you so much for all the links and suggestions, very helpfull! :slight_smile:

The blinds are not really that heavy, they move sideways and rotate, both with the use of cord in a loop(Don't need to use a lot of force to move them, the moving side ways is probably the heaviest task.

hey guys im about to start the same project! your doing vertical blinds like mine. I was just wondering what size motors you ended up going with?

I would use a servo or two. Attach it to the kind of blinds that don't use a twisting pole but simply use a pull-cord (Not the kind with the locking mechanism. Cool project idea!