PC as a temp control device

[noone_particular]

This seems to fit equally well here and in hardware. I'm looking for both hardware and software that will enable a PC to monitor multiple temperature sensors and activate external devices (blowers, pumps, vents, etc) based on the relationship of the temperature readings. Anyone know of sources for either?

[o1ofuis4u]

Some of the fan controller bays may work. They have temperature sensors for in the box, but you could route one of them out of the box, and you can set the temp ranges for when to turn on a certain fan. I guess take the fan cable out of the case, and hook it to a circuit that when it detects a voltage, it turns on the blower or other devices.

Off hand, I don't know of any currently produced devices.

This white paper might have more info for you:

http://arxiv.org/ftp/arxiv/papers/1009/1009.4992.pdf

[Pedro]

Not a computer, but that sounds like a job for something like an arduino board, or a Zelio (a programmable relay, sort of a cheap PLC).
Both require learning a new language. Zelio's use ladder or fdb.

I'll watch this thread with interest, as i don't know how you'd do this with a PC.

[noone_particular]

I know there's programmable industrial units that can handle these tasks. Used to service an old X-Y cutting table that used a TI sequencer, ladder logic, and I/O modules. Brings back memories from when that machine went down and the boss handed me the job of making it run again.

I was hoping to sub an old PC for the controller, but I'm suspecting what I want will have to be custom made or at least custom assembled. Arduino looks interesting if it can accommodate the interaction I want. If it helps, this would be for integrating solar panels, passive heat storage, a couple of greenhouses (as both heat sources and heated areas), integrating with living space environmental controls, and possibly hot water. It would need to control blowers, dampers, vents, a furnace, etc.

[Pedro]

That's a lot of inputs and outputs. I think you know this but, i'll say it anyway.
You need to make sure how many I/O's, how many are analog, how many are digital, what kind, and so on.

From there you can assess your needs better. Zelio's are certainly more limited compared to a full blown PLC in that regard, not to mention programming logic and so on - but for temp control and what seem to be your needs, the relative programming simplicity may not be a limitation, and a Zelio is certainly (much) cheaper than a PLC.

Arduino i don't know so much about, but i am planning on getting one to play with. It has a large community, being an open source project and all, so you may have other people's experiences to look at. Cheaper too.

[Pedro]

Forgot to mention, there are competitor alternatives for Zelio's of course, from Omron for instance.

And you can download Zelio Soft (used to program a Zelio) for free and check it out. At least you can see how to program works, play with it. It can be used to monitor a relay with a PC, or simulate one.

Obviously, arduino's software is free/open source.

[noone_particular]

Therein lies part of the problem, laying out a design without some idea of what is available. The outputs are strictly on/off, blowers, mechanical actuators (dampers and baffles), relays, etc. The temperature sensors and the logic that they operate would be a bit more involved.
Ex:
If X1 > X2 < X3 = Y0 out
If X1 > X2 > X3 = Y1 out

It's been a long time, but I think I can handle the logic. ATM, identifying and locating the specific components is the problem.

[Bill_Bright]

The outputs are strictly on/off, blowers, mechanical actuators (dampers and baffles), relays, etc. The temperature sensors and the logic that they operate would be a bit more involved.

If it helps, this would be for integrating solar panels, passive heat storage, a couple of greenhouses (as both heat sources and heated areas), integrating with living space environmental controls, and possibly hot water. It would need to control blowers, dampers, vents, a furnace, etc.

That helps a lot. How distant are these remote locations? Feet? 100s of yards? Or miles away? Sensors would be, IMO the easiest - stick the probe where you want it. It is remote monitoring of the sensors that becomes the challenge.

I'm looking for both hardware and software that will enable a PC to monitor multiple temperature sensors and activate external devices (blowers, pumps, vents, etc) based on the relationship of the temperature readings

That seems pretty complex and something I would expect in the control room of a nuclear power plant. Is this place a commercial business or just a personal project at your house? It seems a simple $20 thermostat from your local hardware/home improvement store (or even Wal-mart) connected to your environmental devices (blowers, vents actuators) would work. That would not serve your monitoring requirement, but it would protect the hardware in those remote locations - and establish a "living space environment" for stashing the mother-in-law.

That said, if this is a small, personal project at your home and these greenhouses with "living space environmental controls" are pretty close to the house, I recommend you look at smarthome/home automation products. It already is a well established industry with a wide selection of "off-the-shelf" products for this very purpose - to include monitoring via your computer, from any Internet connected computer, or "there's an app for that" for your smartphone that lets you turn on or off lights, open or close blinds, lower the thermostat or turn on the coffee. There are whole house designs or discrete products, as seen in recent TV ads for new garage door openers you can control remotely.

[o1ofuis4u]

Didn't think of controllers using ladder logic, great idea.

[noone_particular]

This is for an at home business. The distances are fairly short. No need for wireless. The wiring won't be that big of a deal. Standard thermostats are not capable of what I need. The output states will largely depend on how the temperature on sensors compare to each other. Some like the residential and the greenhouse minimum/maximum temperature sensors will be relatively fixed or seasonal, but where the heat comes from will depend on the temperatures of the other locations, eg solar panels, heat storage, etc. The greenhouses will be both heat sources and destinations. The logic is fairly easy as long as the controller can accept temperature values as inputs and can control outputs based on greater than or less than equations.