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.
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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.
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Signing UpStep 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
TOTAL $15.90
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
RECOMMENDED SUPPLIERS:
BG Micro
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.


















































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Also, BGMicro didn't have the REL1090 on its site, so I ordered REL1107, the description is: 5Vdc Latching relay by Fujitsu. 2A contacts, double pole, double throw latching. Coil resistance 178 ohms. Will fit in a 0.3" socket.
Will that work? Or could you suggest a replacement relay I should get?
I'm looking forward to this project, I have a background in programming, and it's fun to see the picaxe is programmed in BASIC, line numbers and all!
My proposed solution is to run the motor directly off the batteries through a separate relay, so that it draws from outside of the voltage regulator. Fortunately I ended up with a double relay DS4E-S-DC5V, since I couldn't find the one you recommended, so I'll use the other side for the motor control.
Thoughts?
Also my application is different. I want my blinds at work to close when the sun is out, to reduce glare on my computer screen, but then reopen when the sun goes behind a cloud or a building. I hope to redesign it so the two buttons are used to increase or decrease the programmed setpoint for the desired amount of light. And the algorithm would sweep the blinds from closed downwards through fully open to closed upwards, recording the maximum amount of light that comes in. After determining the maximum available light, it would then close them fully down and gradually open them until it hit the setpoint or the maximum available.
Even with the motor disconnected, it still resets once in a while. I've used 2 relays now, and have connected the motor (and the switching sides of the relays, of course) to a completely separate power supply. The only thing the PICAXE is doing (through the darlington array) is switching these relays.
Still, it resets now and again. I bought parts for two devices and have been swapping them in and out to try to blame manufacturing inconsistencies.
Oh yeah I have three 220nF capacitors across +5V/Gnd, without these it doesn't work at all, just resets all the time.
From what you describe this still sounds like electrical noise in the circuit. It could be coming from the motor and/or relay coil. I have two suggestions.
1) Put a 220 nf polyester capacitor across the relay coil to suppress any noise coming from it.
2) Try operating the circuit on battery power. If you have to add capacitors to the 5 volt supply it must be really noisy. If the circuit operates fine on battery power then you need to either change power supplies or add several thousand mfd of capacitance to the output.
I hope this helps.
I am on batteries. Well, my electronics are on batteries. The motor is being powered by a cannibalized 5V supply, but it's completely electrically separate now, being switched by the relays.
I've also ordered some other relays off of ebay, just to try them.
If only I had an oscilliscope to see the noise pattern.
My program is super cool by the way, I'll post it when it's all working. I couldn't rely on the blinds making the motor stall out at the end of the rotation, so I have to avoid that by tracking my "position" as the total time spent swiveling each direction. To avoid drift I'm resetting it every 12 hours or so that the midpoint is the location where the maximum light was observed. So it's getting complicated.
im a newbie to electronics im really intrested in this idea.how would i put it on a timer as i need it to open at 10am and close at 6pm every day for 12weeks each year (its for my racing pigeons)
You mention using a household timer, but I have never done any circuitry before so I'm not sure where to start with that. Using the 08M2 would allow me to follow your design fairly closely.
BTW, I want timed blinds to help keep the house cool in the summer and to help wake me up in the morning.
Any tips would be greatly appreciated! If I figure something out I'll post the solution here.
The motor he listed above is 3v, that would only take 6 3x6 panels at $.60 each (typically), removing the need to change batteries and would only open on days that were sunny enough to deserve the blinds to open. 6 panels would give only 12 watts of power, but if geared right should be enough to slowly open them.
The only thing I worried about is that it might burn out the motor keeping a charge on it all day, everyday, no?
I think you might have misunderstood my goal.
You are talking about delays, capacitors, circuits, etc.
But I am looking to have NO circuits, batteries, or light sensors to determine when they open or close. (I don't think I would even need the voltage regulator because the cells are not capable of generating more then 3.2v in the brightness sun.) I was thinking that I might use a DC to DC boost converter to keep the voltage at 3v as long as possible.
Due to a spring on a pulley line, the natural state of the blind would be 'closed'. When the sun hits the panel, it puts voltage to a motor, pulling the line, stretching the spring, and holding the blind open. If it gets cloudy or sun goes down, there would not be enough voltage going to the motor and it would lose power and the spring would take over and pull the blind back to natural state of 'closed'. So as long as the solar panel outputs voltage, the motor has power to fight the spring.
The motor would be geared and open VERY VERY slowly with the small amount of power the solar is giving it, so the motor would really not have that much constant power going to it. I am guessing 3v with 12w at the sunniest part of the day.
Is there any type of motor that can handle the constant voltage or maybe some other idea similar to this.
Thanks,
Gary
$10 a motor
3v -3 rotations per min- (very slow eh)
http://www.ebay.com/itm/3V-3RPM-Torque-Gear-Box-Motor-New-/260793928051?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cb8878973
or 3v 10RPM
http://www.ebay.com/itm/3V-10RPM-Torque-Gear-Box-Motor-New-/220765783849?pt=LH_DefaultDomain_0&hash=item3366aa8729#ht_4685wt_952
Boost converter (but I need to find one that will do 1.5v to 3v)
http://www.ebay.com/itm/300601910406?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_3634wt_952
I did understand your goal.In theory the method you are talking about using would not need anything more than a bank of solar cells, a spring and a motor. However, I do not think there is any way to do it this may for a couple of reasons.
First you cannot allow current to continue flowing through a motor when it is stalled because its inductive resistance drops dramatically when its stops turning. The motor windings will then act like a short circuit and the current flowing through them will increase and cause them to heat up and fail. There is no way around this. If you limit the current so this doesn't happen then there won't be enough to start the motor. All motors use several times as much current to start as they do to run. Also, all motors pull more current when the armature stalls. If the solar cells you are using can supply enough power to start the motor they will supply enough current to damage the motor if it stalls.
As for using a spring to return the device to the original starting position once the motor looses power, it sound good in theory but I don't think it is likely to work for this reason. When the motor is opening the blinds it is also going to have to wind up and hold the spring as well. This is going to dramatically increase the needed electrical current and the motor size needed to overcome the friction of opening the blinds and the current needed to overcome the spring pressure. That is going to require more solar cells to increase the current and the additional current will only serve to fry the motor faster once it stalls.
Also, you mentioned using a very slow gear motor. That will work great when it comes to opening the blinds but it is going to present a serious problem when it comes to letting the spring close them. The best way to understand this is to take a small gear motor and try to turn it using pliers on the output shaft. This is what you are thinking about trying using a spring on the output shaft. With a 1 to 3 rpm gear motor you are going to damage the gear motor before you get it to turn using the output shaft. I cannot even turn the gear motor I used in this project using the output shaft without using excessive force.
I hate to be such a skeptic and I do not want to discourage you but I don't think this is going to work. Perhaps there is some other way. A slip clutch on the gear motor output shaft may prevent the motor from stalling once the blinds are open. The motor could keep turning and keep tension on the shaft until the sun goes down and you loose power. However, even with that you are going to have to get the spring to turn the output shaft in reverse to close the blinds. Again, the extra power needed to wind up the spring to this incredible torque (for such a small motor) is going to be a limiting factor.
You have some really great ideas and I am sure there is some way to do this simply. I just don't know how. I suggest you get some motors, solar cells and springs and give it a shot. Even it it doesn't work you will gain some knowledge. Best of luck and please do keep my informed.
I think with a small guide on my line that would flip a manual switch at a certain point and have it shut the motor off at least I can have the blinds all nicely opened and the sun shining in when I wake up. Then just use some sort of quick disconnect that I can release the line manually at night.
If what your saying is that once the slow gear motor is off, it wont turn back on its own, then I just have to make the spool that collects the line, be able to 'pop' off the shaft and unravel the line, then 'pop' it back on once the blind is down, resetting it for tomorrow.
halfway is better than none :) (for now)
Thanks again
This is really awesome.
Could you please give me the plan and instructions how to build this, I wanted one for my coop, your help is really appreciated.
Thanks
brbd@hotmail.com
Any other ideas or suggestions would be appreciated!
thanks
My students are having a difficult time with the schematics. We need to complete this project asap. I have tried sending a private message. Is there any possible way you can contact us? Thanks Ms. K at thelma.kastl@ashe.k12.nc.us
Did you use the IR Detector in place of the LDR?
Does it have to be a universal remote that is needed for the codes or could i use a different one?
Where and how would you you use the 2 pots?
Many tahnks for taking the time to answer my Q's
Ben
You will have to use a SONY TV remote control, or as in my case, a universal remote control setup for a SONY TV since the PICAXE only reads SONY TV IR codes.
The Pots - Since the guy I worked with on this project lived 800 miles away from me and know nothing about PICAXEs, I used the pots to set two variables on the PICAXE inputs. The PICAXE code then read those variables and used them to time the motor that opened and closed the blinds. It worked great. Increase or decrease the resistance on the pot, increase or decrease the time the gear motor turns to open and close the shades. This worked much better than the method of programming the PICAXE by trial and error to get the timing just right like I did on the original blinds unit I made.
and where were the pots located in the circuit?
Sorry, i'm not the best at circuits quite yet.