Temperature Controller Help Required

After many months of trying to teach myself how to write a program for a pic micro to control the temperature in my greenhouse propagator I must, with reluctance, admit defeat.

I would be grateful if any elektroda member could design a circuit and write a program to control the temperature in two different zones between approximately 15ºC and 30ºC and display the current temperature in these zones on a single LCD.
A means of setting the temperature would be necessary.

I would prefer the circuit to use thermistor beads for the sensing element (so that the sensor could be placed in the seed medium at seed level).

Also I have seen vivarium thermostats which use pulse-proportional control and would like to use this if possible, to prevent large hysterisis.

I am prepared to pay a small fee to anyone who can help.

Try: h**p://home.no/fsan/projects/ There is a temp. control project, with LCD, clock, etc...

I would guess that even if someone had a very similar project and was able to port it to your needs that by the time they had finished with a prototype they would have over a hundred hours in it, so you might consider continueing on your own. I would point out that this project becomes orders of magnitudes simpler if your controller is connected to a PC.

To help aide you I suggest that you tackle this project in well defined steps. You can most likely find all of the building blocks in projects like the ones posted above. You will simply need to patch the code together and resolve any resource conflicts that arise. I might suggest that FLASH based MCUs and a Bread board will greatly simplify your design process by affording you the opportunity to test each block as you go. When everything is working to your satisfaction, then you can design a PCB and burn it for your final assembly.

Fish

Hi oldmp and Fish4Fun

I thank you for your comments, and will keep trying to work this out myself.
I have found various texts and examples on the web and I do subscribe to the online edition of EPE magazine which has many Pic projects and tutorials, however its the programing that I just can't seem to get my head around.

Who knows, maybe miracles do happen :wink:

thanks again
rahnette