[oopic] Re: Cooling control system

--- In oopic@yahoogroups.com, "cha_aman" <popa-r@...> wrote:
>
> I'm looking at using an oopic to monitor temperatures and activate a
> cooling/heating system as required, and to display system status
>
> Temps monitored will be:
> Averaged Ambient External (2 samples)
> Averaged Internal Ambient (2 samples)
> Averaged Internal Core (2 samples)
>
> the H/C system will attempt to maintain an even temperature
>
> the display:
> Will consist of colored LEDs arainged into a 4x4 grid
> General temp (hot, warm, good, cool) for each of the monitored temps
> and whether the H/C system is heating, idling, off, or cooling
>
> I was wondering if anyone had suggestions about boards to use or how
> to configure them (I'll worry about programming later, have to
> decide on layout and components first)
>
> I was planning on using a seperate display board that would link to
> the temp controller. Do I need a seperate board to collect and
> weight the samples, or am I overlooking anything?
>

I would wander over to Maxim (www.maxim-ic.com) and find some SPI or
I2C based LED drivers. Maybe the MAX6966 is a candidate. Using these
devices will allow you to drive the LEDs without taking up all the IO
pins of the OOPic.

As a practical matter, the R board is handy but you can't get to 6 A/D
inputs. I would use the S board and buy an RS232 level changer for
the serial port: http://www.pololu.com/products/pololu/0126/

Or use
their design on your own board. The S board really just uses a 40 pin
DIP package. No reason not to dump the board and keep the chip and
EEPROM. But the board is a nice way to prototype.

You biggest problem will be temperature sensors with an output that is
meaningful over the temperature range of interest while producing an
output voltage that swings over a large part of the 0-5V input range
of the A/D port. You will have to do some research on sensors and
their output swings. You can offset and rescale the sensor with a
single op amp using the information in Chapter 4 of "Op Amps For
Everyone" http://www.ti.com/litv/pdf/slod006b

Richard

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