Saturday, September 8, 2012

Home Automation - Practical Application

It was a nice rainy morning in the desert and I decided to open the doors and air out the house.  I had all the doors open and the breeze, laden with the smell of wet earth, was circulating through the house removing all the smells of being locked up during many days of 100+ (F) temperatures.  My new puppy was trying his legs out running from doorway through the mud to another door and through the house and out again; a really fun morning.  Of course, I turned off the A/C compressors and let the recirculate fans run to air out the ducts in the house. This saved me a bunch of money on power since the entire house load was around 2KW even with the pool pump running.

This pleasant interlude started just before dawn (puppy had to go pee) and lasted until 9:30 AM when I shut the doors, put the puppy in his crate and took off for an early movie.

After I got to the show I realized that I hadn't checked the garage door and OCD set in worrying about the darn door being open.  I took out my phone and pulled up my web site to see.  Well, I had shut the door, but I forgot to restore the A/C to its summer settings and the dog was in a desert house with no cooling.  In most instances I would have just let the dog deal with it, but I had other choices now; I just touched a control and the A/C was restored to summer settings and started to cool the house down.

I have remotely checked the various statuses of my devices while away on trips, both to brag about having the ability and to actually make sure things are OK.  Also, I have daily instances of the various controllers taking care of things for me.  Things like making sure the pool pump is turned off at 10PM so it doesn't run all night, the acid pump automatically injecting chemicals into the pool to keep its levels reasonable, and my thermostats automatically handling peak usage to reduce power costs, but this is one of the rare instances where I actually wanted to remotely control my house.

That was so cool!  The puppy seemed to appreciate it too.

Friday, September 7, 2012

Battery Charging - Part 4 (Harbor Freight item 42292)

Part 1 of this project is here, part 2 is here, and part 3 is here.

I probably will never actually finish this project to my satisfaction.  If you have been following this for the last many months, you might remember that I started off trying to get a float charger for lead acid batteries that actually worked and didn't dry the cells out in a couple of weeks ruining the batteries...without paying U$50 or more for each of them.  Rural living requires a lot of batteries for various machines that we use a few times a year and it is really annoying to have the battery fail between uses because of inattention.  Anyway, the latest charger variation (see part 3) works really well to keep the batteries charged with minimal loss of water, but checking on it is a pain in the butt.

I have to hunt down a multimeter and traipse out to the barn and check the voltage on each device.  It would be nice to have a voltage indicator on them to tell me if it is working correctly.  So, off to ebay I went and ordered a few of these:
These little guys just hook to the wires and get power from the source being measured.  Not the perfect situation since you have to power the LEDs from the supply that you are using, but it's a battery charger, not a lab instrument, so this will be fine.  To test them, I just hooked it to the charger output and stuck it on the wires leading to the battery on one of the cars.  This thing is cool.
The actual measured voltage is 13.4 on my multimeter, so it is relatively accurate and it gives me a highly visible indication of the state of charge from across the room.  Now, I have to figure out how I want it hooked into the circuitry and what form factor I'll use for mounting and using it.  The little black box I have in-line won't do the job, so I'll have to look around for something to house the display.

This brought up another idea: suppose I use one of my XBees and transmit the battery voltage over my network?  I could then check the state of charge from anywhere (yes, anywhere in the world) any time I wanted to.  I could even set up an alarm to send me email or a text message when something went wrong like a rat eating through the wiring.

I know what you're going to say, "What happened to the U$50 price goal?"  I don't have a good answer to that question; the parts and pieces so far are around 15 bucks, the little voltage display cost me a little under 3 bucks, and now I'm looking at an enclosure and an XBee.  This will push the total cost up into the 40+ range.  

I guess I'll just have to compromise my principles.....