Homebrew Arduino setpiont differential controller done!

[WoodNotOil]

It's finally done and it works! I have successfully built a control for loading my storage tank. It uses an Arduino USB board, 2 DS18S20+ Dallas 1-wire sensors, a solid state relay, resistors, a transistor, and a dc power supply. I have the Arduino board up by my computer to easily access the USB cable and all the rest of the electronics down by the heating system. 50' of 6-wire phone wire connects the two. The sensors read the temperature going into my flat plate heat hx and the tank temp. The software I wrote for the board allows the setting of a differential and a setpoint for the tank to get to. Based on the readings, the setpoint, and the differential it turns the pump on and off. Very accurate, easily tweaked, and all for $65 in parts including the board. You can see some pictures and preliminary documentation here (broken link removed) . I will be expanding the page as I have time. Questions and suggestions are always welcome. I am just excited it actually works!

 

[chuck172]

Great job, I'm sure that will be a big help to many of us. The Tekmar controller made my life much easier.

 

[Nofossil]

Congratulations! Welcome to the not-so-exclusive woodburning geek club! That's an awesome writeup on your web page, too. I think I'm just going to have to play with the Arduino in my copious free time.

 

[WoodNotOil]

Welcome to the not-so-exclusive woodburning geek club!

Thanks. It has been a lifelong dream of mine to officially be a "geek." It finally happened... :cheese:

Nofo - you definitely have to get into the Dallas 1-wire sensors if nothing else. You can't beat all your sensors on one wire. Once you get the id it just spits temp readings out at you. No need to convert mA or anything. They are very cool. I like the arduino for price and simplicity. It uses the USB really as a serial and you can write monitoring software that gets the data that way instead of having to feed it to a server or wirelessly. That is my next step. I would like to add sensors and log data ideally.

 

[cguida]

Way to go WoodNotOil!

Very impressive, and so economical... I'm in the process of making up a Jameco order, and I will try to get two of the Dallas Semiconductor 1620. I was more than a little intimidated by the digital output and general complexity compared to the LM34. But you make it look so easy.

I have to admit that I haven't even started experimenting with the arduino. I will get to it eventually, but in the meantime, I found that since my heat exchanger was actually a zone in the existing sytem, I could toggle it via the thermostat line. (The tank circulator gets its power in parallel with the system-side zone ciruclator. So the thermostat line can control both pumps.) Anyway, emergency dump aquastat on the wood boiler now toggles the tank on at 170 degrees (tank is the new dump zone); and the aquastat in the oil burner calls for heat from the tank when the oil biler temerature drops to around 120. (Boilers in series). This works, but it is not adaptive the way your system is. Also, in order to 'appopriate' the oil boiler aquastat, I had to disconnect the oil burner. In weather like this, not having oil really focues the mind on the state of the fire(s).

Did you post your controller info on the Arduino site? I'm sure people there would like to hear about it.

Again, congruatulations. Keep us posted on new Arduino adventures.

 

[WoodNotOil]

Thanks Smee. I should give credit to you for turning me on to the Arduino boards in the first place. I should also credit Phantom from here who helped me out on the Arduino forum as well with the code end of things. I will be sure to update my posts on the Arduino forums as well so that the info is there for those who need it.

 

[WoodNotOil]

My tank hit the 175* setpoint this evening and turned the pump off all on its own. That is the first time I have gotten it up to that temp and now I don't have to worry about losing heat as the Tarm comes down in temp. It seems almost too easy... It will be interesting to see how long we can heat off of storage...

 

[Blevesque]

Nice work! Are you still planning on doing a detailed writeup on this. For us not so control wiring saavy folks. Brian

 

[free75degrees]

Very nice, it's cool to see people do things that haven't been done before.

 

[WoodNotOil]

Nice work! Are you still planning on doing a detailed writeup on this. For us not so control wiring saavy folks. Brian

I will be expanding my write up here (broken link removed to http://woodnotoil.googlepages.com/arduino) . It would be helpful in doing so if I knew exactly how much detail people would find useful. Give me some specifics on what you would want to know. What pictures would you like to see. Thanks for the feedback.

Very nice, it’s cool to see people do things that haven’t been done before.

Exactly why I did it. I think the more variety and documentation we get of projects the better off this community will be. I don't know much about the electronics side of things and have really enjoyed figuring out this first project. I hope others can use it as a basis for more complex controls. The possibilities are there for some really neat stuff.

 

[Medman]

I'd like to know how the sensors are mounted. I have them here on the desk, and the software is loaded in the PC. I'm just waiting for the Arduino board to arrive.
Thanks for all your pioneering on the controller. I am sure it will make installation and operation of my storage more efficient.

 

[WoodNotOil]

I connected them with some extra phone wire I had laying around. The sensor in my well is wrapped with aluminum foil so it fits snugly in the well and the other is strapped onto a pipe by wrapping it with several layers of alum foil, a piece of pipe insulation over that and then I wrap electrical tape around the insulation to make sure it is snug. I have found that a +5* calibration is needed to get accurate temp in the strap-on application, but that the well is extremely accurate. Good luck with the project. I am glad that several people are already making use of my information.

 

[Blevesque]

Hi Wood, how many sensors would one be able to add to one of these boards? Also it looks like everything with exception to the arduino, the solid state relay can be had at Radio Shack. Where did you purchase the Arduino and the solid state relay, also what is the part number on the relay? I think thats it for now. Thanks, Brian

 

[WoodNotOil]

Hi Wood, how many sensors would one be able to add to one of these boards? Also it looks like everything with exception to the arduino, the solid state relay can be had at Radio Shack. Where did you purchase the Arduino and the solid state relay, also what is the part number on the relay? I think thats it for now. Thanks, Brian

I added some links to the specific parts and places I got them for you. (broken link removed to http://woodnotoil.googlepages.com/arduino) The transistor I had on hand from an old defunct project. I also gave an alternate that Phantom suggested for the relay. If you are going to control more than one device, something like that would be nice. I am sure you can hook a lot of those sensors up to one pin, but there is probably a limit due to power consumption. I know that you can run a bunch more on another pin if needed. I can't imagine with the 1-wires a situation where you couldn't run as many as you need for your system. Perhaps Nofo or someone else knows what the limit per pin would be?

 

[cguida]

Hi WoodNotOil,

Someday soon I hope to try to do what you have done. But meantime, you might enjoy this picture of my new Control System User Interface as seen from the top of the basement stairs -- 7-1/2 lightbulb in parallel across the tank circulator. There's a similar small bulb across the wood boiler circulator that tells me if the fire is still hot.

I got the system cheap from PatchWork Solutions, Inc. The installer, one Mr Slap Dash, even left me with a concise operator's manual:

"If the lights are bright, we're all right.
If a light is dark -- time for more Twigs and Bark."