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This is a project in progress. I am posting this so it may help others with similar projects.
Scope:
Control a HVAC humidifier based on OUTSIDE air temperature and INSIDE HUMIDITY.
Prevent moisture build up on windows and doors during the winter time from too much moisture in the air.
Winter time here in Michigan can see temperature swings from -15F to 45F (-26C to 7C) during the winter months. Unless you manually change the humidistat settings condensation will form around windows and doors leading to damage and mold. I have read many a post where people have built temperature / humidity displays for various reasons so I got to thinking why not control my humidifier with a PIC and be done with it.
The humidity and temperature readings do not have to be that accurate, so whole numbers will be used. I do have access to calibrated temperature and humidity devices to compare with.
Actual humidity with in +-2% is acceptable and I will be looking at 5% increments.
I also wanted to be able to override the humidity level by +- 5%
The SIMULATION:
PIC used 16F1827 I have about 6 of them laying around and they can easily handle everything.
4x20 character LCD Have two of these on hand as well.
two sliders to represent the Temperature and Humidity inputs.
2 switches to provide the +-5% override. (will be one 3 position switch on my project ON- OFF- ON)
1 LED so I know if the humidifier is on or off (also used in first hook up to do the blink test)
The LED will also be the output to an SSR to control the humidifier motor. (24vac Synchronous type)

I have attached what I have so far.
This is just a start to see if what I have envisioned could be done.
I still have to add several decision trees to check temperature against humidity.
Am not sure of the temperature offset I will need till I hook up the actual sensor. Same goes with Humidity.
I could not use an all in one sensor as the temperature will be out doors and the Humidity in doors.

Will post more when parts show up and I can build the real thing.

Bob

Been slowly building the actual board.
Have every thing finished except an LCD display. Ones I had were bad, no wonder I got them for a dollar each.
Here is a picture of the completed board. I used screw terminal connections for the AC in, the temperature probe , and the switched AC out. The temperature probe is mounted on the board for now but will end up about 20 feet away when everything is completed.
Soon as I figure out how to get the schematic into a Jpeg format will post it as well.

Bob

Hi Bob!

Very interesting project, thanks for sharing with us. You write detailed info will come, but will you already now please tell me the names of the Sensors you use and the AC DC component.

Have you by the way seen John's and others nice Projects here: http://www.matrixmultimedia.com/mmforum ... t11#p44939 I have tested the project, it also works very very well.

Best regard

Jorgen

Yes I will provide a list of the components I used.
I had to use separate temperature and humidity sensors as I am measuring OUT door temperature but IN door Humidity.
I purchased most of my items from MOUSER here in the USA

Humidity sensor is a Honeywell 785-HIH-4010-001 http://www.mouser.com/Search/ProductDet ... H-4010-001
Temperature sensor is a Microchip 579-MCP9700a-E/TO http://www.mouser.com/Search/ProductDet ... 9700A-E/TO
I used a Panasonic SSR and not a relay to reduce components and wont hear it clicking on and off. http://www.mouser.com/Search/ProductDet ... 769-AQV202
A 3 postion center off togle switch http://www.mouser.com/Search/ProductDet ... 1-7103-002

Rest is a simple 5 volt regulated power supply using supplies I had on hand http://www.mouser.com/Search/ProductDet ... 1-L78S05CV

Oh had to use a bridge rectifier as mains supply is 24V AC. this is what the motor run off of and was convenient to use to power the project.
More to come as I write the code.
Bob

Hi Bob!

Thank´s for all your information.

Jorgen