Custom built fan controller for insert

[paulm81]

This is way cool to see, glad this thread got bumped!! I've done some digging around on the internet and have had a hell of a time finding someone that makes a digitally controllable rheostat I could use to get many different speeds and use them with a temp curve. Right now I've got one of those rheostats that the blower plugs into and that controls the speed of the fan quite nicely, but it's manual...

Initial thoughts on doing it on the cheap, a small arduino board to drive a RC servo and monitor a temp probe. The RC servo would hook to an adjustable rheostat and adjust the fan speed, kind of rigged but the cost on all the parts would be cheap. I'd have to program the arduino to do what I wanted, but as a bonus it could hook up to the internet and I could see the status of my stove wherever I was at. (Could even rig an email alert for danger temps or reloads, hmmmm)

Okay, this is getting pretty nerdy for the hearth forums so I'll stop here...

Interesting idea HaTax, how does your fan currently behave with the rheostat, especially at lower speeds? Any issues with noise or motor heating? I assume you're using a rheostat meant for motor loads, not just a basic lighting one.

If the knob on a rheostat just turns a pot, could you replace the output from the pot with a voltage signal from your Arduino board? This would eliminate the RC servo and the mechanical connection to the pot.

I'm not familiar with Arduino, but I just looked at their website and they'd be fun to play around with if I had the time!

 

[HaTaX]

Interesting idea HaTax, how does your fan currently behave with the rheostat, especially at lower speeds? Any issues with noise or motor heating? I assume you're using a rheostat meant for motor loads, not just a basic lighting one.

If the knob on a rheostat just turns a pot, could you replace the output from the pot with a voltage signal from your Arduino board? This would eliminate the RC servo and the mechanical connection to the pot.

I'm not familiar with Arduino, but I just looked at their website and they'd be fun to play around with if I had the time!

It was here with the insert when I bought the house and looks like it wasn't originally purchased with the stove, there's an on/off switch on the power cable for the blower and the end of the plug goes into this rheostat. It looks pretty much like this: (broken link removed to http://www.northlineexpress.com/dial-a-temp-rheostat-4008.html)

Yup it's an induction motor rheostat for sure, and I've never noticed any ill effects on the blower motor itself. The blower motor is probably 30 years old as well, it has manual oiling points for both sides of the shaft that I put some 3-in-1 into once a year. Motor operates just fine at all positions on the 'stat, aside from the odd buzz at certain RPMs that is just the thin metal finding the perfect spot to vibrate at. Not 100% sure on the heat from the motor, but the cage has never felt too hot to me and it sits directly under the ash lip near the firebox, I can't imagine it's a very cool location to begin with. You can easily see the motor through the mesh of the cage so I'll try hitting it with the IR gun over the next few days... Adding to this, the motor also has a small fan on the other side of the shaft that is designed to cool the motor, it's about the same diameter as the motor itself and doesn't serve a purpose beyond cooling the motor.

It's always been noisy at full speed, but it moves a ton of air through that box so I haven't complained too loudly. Also looking at current blower replacements, it's kind of depressing... The motors themselves look significantly smaller and cheaper, and I see plastic bits used here and there. The only plastic in this blower cage is the insulation around the power cord coming into it...

That is a great idea to just output the needed voltage from the arduino in place of the potentiometer! Maybe I'll take the screws off it and check it out with my meter, that would save a ton of time programming as well as fabricating something to connect the servo to the 'stat.

 

[paulm81]

I'm very interested to see if a variable speed controller would be that easy to build. Custom alarm points would be no problem to program, maybe even a damper control! I just built mine, but now you've got me thinking of upgrading!

Is it possible to have a digital temp display with the arduino board?

 

[HaTaX]

Sure can! You can go either with a 2/4 line black and white display for around $10, or you can make a jump to a full fledged color, touchscreen LCD like this for a little under $20: (broken link removed to http://www.sainsmart.com/sainsmart-3-2-tft-lcd-display-touch-panel-pcb-adapter-sd-slot-for-arduino-2560.html?___store=en&___store=en)

I was thinking of the touch screen so I could have a button in there for reloading, coal burndown, and anything else I hadn't already thought of. Makes it very easy to add input buttons without needing physical modifications to the project case.

It looks like others on here have gone down this path, I wonder if anyone has posted their code on codeplex or anywhere else public? If I end up doing this, I'll make sure the code I use is available for others to view and use, having the baseline programming in place would save someone quite a bit of time on the project.

 

[paulm81]

It boggles my mind how cheap that stuff is! Obviously not made in North America.

I am looking forward to seeing your controller!

 

[HaTaX]

Kind of sad there isn't much for manufacturing rapid prototyping systems here in NA, I'd be willing to foot another $10 or $20 for it if it was!

The prices are amazing though, this is a pretty much ready to go system with everything I'd need to get started for just over $60: (broken link removed to http://www.sainsmart.com/arduino-compatibles/new-nxp-arm-cortex-m3-lpc1768-development-board-3-2-tft-lcd-module-64kb-sram.html)

Color touchscreen LCD, Ethernet header, pretty much everything I'd need for the main board all in one package. It's getting tempting....

 

[HaTaX]

I was thinking, if I wanted to take this all the way I could even add in control of the secondary air easily. Using something along these lines:
(broken link removed to http://www.ebay.com/itm/1-2-Magnetically-Latching-Solenoid-Valve-4-5-to-9-VDC-Water-etc-DDT-ML-4-5VDC-/290836349688?pt=LH_DefaultDomain_0&hash=item43b73282f8)

The system could use another temp probe inside the stove itself near the secondaries, once that reaches a set level, the secondary air system is opened.

Actually surprised that you don't see any stove manufacturers that would include some kind of a system like this. I'm keeping in mind operation during power loss while thinking this through, there's no reason a gel cell or UPS battery shouldn't be able to run a system like this for quite some time. The trick is to use the correct components along the way to minimize power draw. I've seen the smart stove system, and am basically thinking along those same lines, but with a control in there for the secondary control as well.

So many ideas, so little time...

 

[scooby074]

Great build paulm81!! Something Ive been thinking about myself.

I just got through building a custom PID based thermometer with alarm that reads both stovetop and stove pipe temps. I agree that those ebay PIDS are crazy cheap! Don't know how they do it.

Low cost PLC's and those Adrino controllers are really opening this field up.

HaTaX, I look forward to your build too!!