Heating controller

[djmartin1]

I am looking at the IsoPod to control a multi-zoned furnace. It would have the ability to have multiple temperatures per each of the days of the week. And, be able to log temperature data to a PC. And, be able to be controlled from a PC. Is this the best unit? What should I use to detect the temperature? Control the furnace, it is 24 VAC with one contact for starting up the heat and another contact closure for turning the heat off (It would be nice to have a solid state switch). And, would I need a clock chip to keep track of the date/time(the PC would be connected most of the time)? Do you have a schmetic for me/program, parts list, where to buy the parts? Any suggestions would be helpful. I have a good programming background and can wirewrap parts to the developer kit.

[RMDumse]

The IsoPod(TM) is an acceptable microcontroller for the task you suggest, but I don't know if I would say it is the best. The advantage of IsoPod(TM) is its high speed. But this comes at a cost of higher current than lower speed processors. So if you want to keep running when power is out, the IsoPod(TM) will burn batteries faster than a lessor processor.

The IsoPod(TM) has 12 bit A/D which will read finer detail in temperature, but a F68HC11 processor with a 8 bit A/D could read most room temperatures from colder than comfortable to warmer than comfortable to a quarter degree already.

The IsoPod(TM) has several communications options, having two serial channels and CAN which might make it easier to talk to a PC.

It has no real time clock, but that is easily overcome using one of the 16 internal timers as a time base. Again, though, this will not hold the time through power down.

What you use to detect temperature can vary widely. It might depend on how far separated the various sensors are located.

The 24VAC can be switched with a bidirection opto isolator very nicely. Consider looking at www.digikey.com for parts.

[djmartin1]

What is this CAN communication standard?

Power is not a big deal since I have a UPS for all my computer items.

The most important temperature sensor will be local. The other optional ones will be a maximum of 100 feet away. What should I consider a thermister or a separate digital chip?

I have a bunch of other projects I would like to create. And, I would rather have overkill and just learn one microcontroller.

The second project I would like to create is a device to monitor several aspects while someone is sleeping. From heart rate to breathing (in very fine detail).

What time chip would you recommend that has battery backup?

[rlinder]

For Real Time Clock, look at DS1305 from Dallas Semiconductor. It uses SPI to talk to host and has dual power input plus a trickle charge output.
For Thermometer, look at DS1722 from Dallas Semiconductor. It uses SPI to talk to host.

These are my choices for my home cooling project.