For a long time I just waited until I got home in the afternoons to open my blinds, but my plants suffered from a lack of light. They were not dying by any means, but they were not healthy, and their growth was severely stunted. I needed to find a way to open and close my blinds automatically when I was not at home.
An automatic blind opener is not a new invention. They have been available for years. However, even the low end models cost in excess of a hundred dollars per window. Some models and styles can cost ten times that much. Most use IR remote controls. Other available activation options include timers, RS-232 interfaces, and light sensors. I needed a controller with a light sensor that would open my blinds in the mornings and close then in the evenings. However, I was not willing to pay what I thought was an unreasonable price for a simple light activated motor. Being the Maker that I am, I knew I could design and build what I needed and do it for a lot less money than what any commercial units cost.
Because I am a big fan of the versatile and inexpensive PICAXE microcontrollers, it was a given that I would design and build my window blinds controller around that chip. I decided to use the PICAXE -08M which is an 8 pin DIP with loads of features including several inputs and outputs, analog to digital converters, a pulse width modulatior, an IR transceiver option, and more features and extras than you would think would fit into its tiny package.
If you have not used PICAXE microcontrollers before I would suggest purchasing the 08M starter pack for around $12.95. It comes with the micro controller, a software CD, a serial download cable, a proto board, a battery holder, and all the basic parts you need to get started with the PICAXE system.
PICAXE 08M Starter Pack
The PICAXE system was originally designed for educational use and is. It is an excellent system for beginners and experts alike. The PICAXE software is simple to learn and use. It uses simple Basic commands that are easy to understand because they actually make sense. You even have the option of writing programs using flow charts. I usually start my projects using flow charts option and later convert them to Basic commands when I start tweaking the program. Best of all, the PICAXE software is freeware. You can download it and all of the manuals from the official PICAXE website.
Official PICAXE Web Site
I must admit that I got a little side-tracked in the beginning of this project. I decided to play around with the IR remote control options built into the PICAXE -08M. It was neat to use an old television universal remote control to open and close my blinds at will, but that did nothing to help solve my problem. I finally found my focus again and went to work designing this project.
After several weeks of electronic hardware, software, and mechanical tweaking I finally came up this design. It is simple, easy to build, does a great job, and is just plain cool. If you have any spare or salvaged parts lying around you can build the whole thing for a lot less than $15.00. If you have to buy everything you can still build this project for around $20.00 including the batteries.
I really enjoyed designing, building, and tweaking this project and I learned a lot in the process. Now my plants get the light they need, my other projects are not shining through the open window blinds at night, and I feel better knowing the blinds will close at night whether I am there or not.
Be sure to check out the "Take it Further" ideas in step 12.
They are sure to spark your imagination and make you
want to fire up that old soldering iron and get busy
on a truly fun and practical project.
Step 1: The Parts You Will Need
- ULN2003A Darlington Array, BG Micro #ICSULN2003 $.59
- DPDT 5.0V Relay, BG Micro # REL1106 $1.29
- Solarbotics GM3 Gear Motor, 224:1 6V, Maker Shed Store or Solarbotics $5.50
- 3.5mm Stereo Jack, BG Micro #AUDCA017 $.36
- 4 X 1.5V AA Battery Holder, BG Micro #BAT1068 $.79
- Battery Snap (9V style), BG Micro #BAT1033 $.25
- LM7805T 5.0V, 1A, Regulator, BG Micro #REG7805T $.40
- Small Project Box, BG Micro #ACS1157 $1.95
- Small Proto Board (2 3/8), BG Micro #ACS1433 $.89
- 8 Pin Dip Socket, BG Micro #SOC1036 $.10
- (2) 16 Pin Dip Sockets, BG Micro #SOC1038 $.08
- Light Dependent Resistor, Radio Shack #276-1657 (5 pk) $2.99
- (2) SPST Switches, BG Micro #SWT1043 $.20 for both
You will also need the following items:
- Resistors: 1 each of 10K, 22K, and 100K (>= 1/4 Watt)
- Wire, solder, small bolts and nuts, Velcro strips
BG Micro Web Site
I am only a hobbyist and I don't spend a lot of money on projects, but the people at BG Micro have always treated me like I was their most important corporate customer. That kind of service is nearly impossible to find these days. Add that to their great parts selection and low prices and you have a winning combination.
Maker Shed Store
Maker Shed Web Site
I love checking out their stuff at Maker Faire
Advanced Micro Circuits
Advanced Micro Circuits Web Site
These people are sometimes a bit slow when it comes to shipping, but it is worth the wait because they have the best PICAXE prices in the US.
Your own stash of surplus and salvage parts.
"To invent you need a good imagination and a pile of junk"
Thomas A. Edison
There is also a schematic below for easier viewing. Right click on the schematic and choose "save as" to save a copy to your computer.