Yeah, shouldn't be too much of a problem to knock up a circuit board. Will probably mill the board if it's a one off. Adding an output for a dash light wouldn't be hard. Could even have a LCD displaying the temperature if you want (the length of the cable run might cause problems as these only run at 3 or 5 volts)
I might even set up a build thread. If this works I'll publish the code and circuit board schematics on here.
Ok the basic code is done. Anyone who wants to see it working a simulation can be found here https://circuits.io/circuits/2788579-vw-t4-stat If you click on the thermostat you can adjust the temperature and the readout and servo should move. The servo is setup at the moment to default to the open position. I still need to calibrate the graduation of the servo to mirror that of a traditional thermostat. Next stage is to build one, for the build I will be using either an IR thermostat or a probe. Any suggestions will be welcome.
I guess it could be nice to see a blue warning light to show the engine is cold if you wanted... This would go out as the stat opens. Would a solonoid be better than a servo? Sent from my GT-I9195 using Tapatalk
Good shout, I've ordered a few different types of sensor including a probe, IR Temp sensor and a laser temp sensor. I'll order one of these as well and see what one works best. I've also ordered a solenoid (pull type, 20mm stroke) and a relay as these things draw more amps than you want going through an Arduino. One thing I am sticking to is that in the default (off) position the servo or solenoid should hold the flaps in the open position.
...and then re-open when warmed up... sounds like an interesting project Sent from my SM-G900F using Tapatalk
Don't forget original stats aren't just on/off. They are gradually opening and closing as the engine warms and cools depending on how hard the engine is working. @top banana racing didn't you dabble in this?
You can get a thermo probe on ebay for about a fiver, infinitely adjustable, just needs calibrating. It was the servo motor I struggled with as I was messing about with central locking solenoids.
@ Brum this looks like a fun idea I have a sparkfun serial lcd here I wonder if I remove the serial backpack I can wire the lcd like yours ( ive never had much luck wiring them like that and always copped out to using the serial backpack board ) I also have some servos a fist full of arduinos and a DS18B20 temp probe .
I would carry on using the serial backpack board and just replace my code with serial calls. There are some good code examples here https://www.sparkfun.com/tutorials/246 The temp probe you have is a 1 wire system and code examples for this can be found here http://playground.arduino.cc/Learning/OneWire
One of the problems I foresee with using servos is that the throw of the original thermostat was only 20mm, now it isn't a problem controlling the travel of the servo but the torque required to activate the flaps might be more that a normal £5 servo can handle. It would be helpful if someone could check the force required to operate the flaps Also what would happen if the servo got stuck, the flaps could then be jammed in the closed position, so we will need a method to check servo travel. One possible method is a simple micro switch that is activated when the servo has the flaps fully open, we can have a bit of code that checks temp against the output of the switch and writes an error to the display or may be sounds a buzzer or even send an email to AA asking for recovery and books you in to the nearest garage (that last one was a joke...............or was it ).
I have a digital temp gauge I built a few years ago using the ds18B20 I've been trying to modify that sketch but I just cant implement the servo part. A little searching online and I found this http://forum.arduino.cc/index.php?topic=388650.0 I've been trying to replicate this but I cant compile it I'm getting a #include <WConstraint> error . which I've never heard of or even seen in that sketch :S (now fixed this) was hidden in the dallas file
