UPDATE: Version 3.2 is live. Read about it HERE.
This is just an update on some thermostat happenings of late. I recommend reading the original post to get up to speed.
DELAY CIRCUIT
I have mentioned elsewhere that I maintain a temperature of 40°F overnight while I sleep. I find that to be a great temp for sleeping, and for saving on propane. It’s a bit rough for getting ready for work in the morning, though. I tried keeping it at 50°F overnight when I started getting a steadier income, but realized just how much propane it takes to get an extra 10 degrees. I decided to add a delay function to the system. I did not want to futz with the complexities of a programmable timer circuit, especially since the RTC chip is not known to be super accurate. I decided a simple delay was best. It’s just a button that increments a delay time. I set the delay for, say, 7 hours, and go to bed. When I wake up the furnace will have been running for about 30 minutes, and its good and toasty.
REMOTE (WEB) CONTROL
I had always planned to introduce the thermostat to the Internet of Things, and finally made that happen this weekend. I’m still debating on my final approach, but for now, Ive gone with the Photon from Particle. It proved to be a REALLY fast and SUPER EASY platform that saved me a TON of headaches and development. No hosting a local web server, no port forwarding, no dynamic DNS. Almost plug and play! I have a lot more work to do. The interface is virtually non-existent besides a simple on/off. I want to get some feedback from the system, like temperatures and runtimes. The problem is the difference in logic level. The Atmel chip uses 5V logic, the Photon uses 3.3V. Luckily, 3V is the threshold for the Atmel pins to go HIGH, so the Photon CAN trigger the Atmel chip. But I can’t safely send any info from the Atmel to the Photon without damaging it with 5v. I’ll be getting some 74 series level shifting DIP chips soon, but until then, I going build a simple voltage divider to tide me over.
My eventual plan is to have my Raspberry Pi operating as the brain of the camper, controlling all the sub systems though a web interface. I’ve gotten as far as running Apache and PHP on my Pi, but its the old (orignal) Model B, and I think I’m due for an upgrade. I’ll write again when the web interface is complete. Keep making stuff!