The Cerebral Forum

Solar Projects => General Solar Projects => Topic started by: Paul L on September 28, 2013, 09:32:05 PM

Title: Solar Blinds
Post by: Paul L on September 28, 2013, 09:32:05 PM
I've been toying with the idea of setting up a set of blinds in my place to be activated when the sun comes up, have the arduino and driverboards shut down during the day, and then have the blinds shut in the evening when the sun sets.  I was thinking about using a photoresistor, and I'm having limited success.  Then I realized that the Heliostat program that Gabriel wrote must somehow figure out the sunrise and sunset depending on the lat. and long inputs.  Is there a way to simply change the program to allow for a setup like this? - or maybe even use it as a "heliostat-blind" to refect the suns rays to an interior ceiling for even distribution of light?   I just happen to have a RTC, easy driver board and an arduino lying around so I though I'd ask.


Title: Re: Solar Blinds
Post by: Gabriel on September 30, 2013, 09:20:45 AM
I suppose you could change the code for this. Strictly speaking, you would only need the parts of the code the help calculate the position of the sun. Then you could just do something like

if sun's altitude > 0
raise blinds

I'm surprised that the photoresistor isn't working out for you though.

I'm not sure a "heliostat-blind" would work out unless you had a blind with especially large "blinders", at least if you really needed to block the light. To reflect the light behind a mirror, that mirror would basically be laying close to flat. Naturally, when blinders are in their "flat" position, they are letting light in. I guess you could just try it manually though and see what happens.
Title: Re: Solar Blinds
Post by: Paul L on June 12, 2014, 10:20:43 AM
So, it's been awhile, but I'm still toying with this project.  This is where I am so far:

-Migrated from a standard Arduino to a barebones ATmega328p to save power.
-Burnt a lilypad bootloader onto the 328p so it runs at 3.3V instead of 5v to save power.
-Implemented sleep code (and interrupts) to save power
-Switched to a more accurate DS18B20 temp sensor
-Added a button to manually set number of steps needed to close blinds and save those setting to EEPROM
-Have a (partially) working override button
-Added IR receiver, so I can now open and close with a remote
-Designed a small PCB

I'm still working on running it off solar, which is not going too well.  Right now, I my breadboard circuit have it running off a 4.4Ah Lipo battery, using a Lipo Rider Pro (outputs 5v) and a small 2W solar panel and then run through a buck converter down to the 3.3v that I need for the uC, driver and sensors.  It can run nearly a month, depending on weather conditions with the panel supplementing the battery.

It's disappointing not to have it work purely off solar since I'm fairly sure I've used all the power saving tricks I can think of.  In sleep mode, the circuit is consuming less than 10mA (I blew a fuse in my multimeter, so can't be sure of exactly what I'm using) and roughly 200 mA when the motor is engaged, which at this time of the year is four times a day - each time lasting roughly 5 seconds. 

In summary, I still have to work some things out, but thought I'd give an update for anyone else out there who may be working on anything similar! :) 

I've attached two pics -
1: Breadboard so I can play. Running off solar and battery.  Using Pololu DRV8834.
2: PCB with remote, using Easydriver.
Title: Re: Solar Blinds
Post by: Gabriel on June 12, 2014, 06:27:03 PM
Clearly you need to build a tracker for the solar panel to solve your problem. ;)