I'm Still Hung Up On Power Failures, but Suppose

OK, OK, maybe I'm a little OCD at times, but that can be a good thing. Folk have been making suggestions, and there have been some interesting pointers given to me, but none of them pass the test. But one suggestion caused a brain storm a little while ago.

A tiny bit of background. It's easy to control a relay or a light, what's hard is the smarts to know when to turn it on, or off. Sometimes this gets pretty complicated. Turn the sprinklers on at 10PM but only if the ground is dry and rain isn't predicted tonight. Turn the porch light on when someone approaches but not during the day. Turn the bathroom light on when someone enters the room, but not if it's after bedtime. We all have problems like that, and the problem is that every time we want to add a little more smarts to the device, we have to do some code and get it on the machine. That often means taking the device out of the box or whatever it's in and carrying it somewhere to reprogram it. Suppose I'm reprogramming something in the attic? It would totally suck having to crawl up there and modify it. Raspberry Pi's are great for this, just use a terminal program like Putty and connect to it over wireless. You can change things, try them, generally mess around until you get what you want and never have to lug the laptop out to the barn to plug it into the chicken feeder.

Suppose I split the work between two computers? One would be fully protected by a UPS that can do all the stuff I need, and another that can survive power failures, but only does the controlling. Let's take a specific but reasonably simple example: sprinklers. I don't need them, but other folk do, so let's take a case of a yard with 4 stations that need to be controlled.

I go out and get one of those relay boards and an Arduino to run it. I can put that in a weather proof box and stick it out close to the sprinkler valves. I will have a power supply wall wart running to it and an XBee to communicate. Arduino's handle power failures well since they have their software in ROM. I only need four command sets:

Relay one on-off
Relay two on-off
Relay three on-off
Relay four on-off

That code would be really easy to put together and implement. Then, I get a Raspberry Pi to send the commands and handle timing and such. I could easily put together menu screens to set the various on-off times, keep track of when they were run, etc. The Pi could be the ultimate sprinkler controller. Of course the Pi would be in a safe place with its power under the monitoring of a UPS that has the correct features.

Let's get a little more complex and consider a swimming pool controller. That would need more relays and possibly some really special features. The basic things I would need in my case would be:

Motor on-off
Fountain on-off
Waterfall on-off
Light on-off

Darn, doesn't that look exactly like the sprinkler control?  Now let's get a little bit more sophisticated and add control to the motor speed and the solar heater. Thinking about it a bit, I only need to add temperature readings for the water and the sun light on the roof to control the solar. Then for the motor, I only need to send motor commands and read their response. I've done all those things with my temperature sensor and pool control projects.

Take the sprinkler idea a bit further by adding some moisture sensors in strategic places with an XBee to transmit the data back to a Pi that figures out what needs to be done and sends back commands. Once again, the brains are in a protected spot with the actual worker computer somewhere else. The Pi could have elaborate software that looks pretty to control the pool and all the features could be made available to a web interface. That would be a fun project, but we might have to resort to battery powered devices to get to some of the hard to reach places.

One of my dreams is to monitor the temperature in each room, gather it in a central place, then control the heat pumps and air handlers intelligently to move heated or cooled air around the house. Little devices that use ROM and can send data would need to be placed in each room, then another simple computer would be placed in each air handler to actually control the fans, compressors and changeover switch. A Pi would be used to look at the data and do something appropriate. I would be able to use any program language or piece of software to develop the smart part from anywhere I feel comfortable working.

So, the various Arduinos would be worker computers that run software that doesn't need to be changed unless I want to add some hardware feature; they do just fine if the power is pulled. The Pi's would be more sophisticated and would handle all the real decisions. They would be backed up automatically and protected from nasty power crap. It would expand my XBee network, but I've got lots of bandwidth there. The other really great thing is that the Pi's can be programmed and reprogrammed any time I want without lugging a laptop out to the sprinkler junction or up into the attic. The PI's could send mail, sms, whatever is needed, heck they could send a signal to an alarm bell just like the big systems. This idea has been sitting right in front of me forever.

I just needed a nudge or two from my readers. Thanks.