xtreme phase change LCD display HELP!!!!

rajanm1 · Post by **rajanm1** » December 25th, 2006, 1:59 pm

i have a custom built phase change unit (it chills the CPU to -50*C for extreme overclocking and benching)
it has a k-type temp probe on it already but currently the only thing that i have that can read it is a special multimeter. what can you suggest to be a perminent option to read the temperature from the probe (i want to mount a LCD on the unit to display the temp)
i am from the UK

thanks

_X7JAY7X_ · Post by **_X7JAY7X_** » December 26th, 2006, 4:19 pm

A HD44780 display, microcontroller, and a MAX6675.

The MAX6675 is a one chip thermocouple-to-digital converter with cold junction compensation.

rajanm1 · Post by **rajanm1** » January 7th, 2007, 10:35 pm

sorry to sound stupid, but i dont know what you mean, please explain as if i have no knowledge of anything

thanks

Post by **mattcro** » January 8th, 2007, 3:01 pm

What X7JAY7X is suggesting is to build your own circuit that forms a thermocouple interface and LCD meter. This requires reasonable electronics skills and some microcontroller programming.

Is the thermocouple to measure coolant temp or the CPU temp? Did the manufacturer provide any info on how to use the thermocouple output?

Jay, does the MAX6675 work below 0 degrees? A quick scan of the Maxim product page suggests operating range of 0-1024 degrees C, but this application (I assume) needs to read down to -50 degrees or below??

I guess you don't have a lot of electronics experience, rajanm1? If not, the best option is to buy a ready-to-go panel meter that has the required range and try to fit into the PC case. Most of these are designed for industrial process monitoring/control. What's your budget for this?...

See for example the Tracker meters from Amplicon (expensive but you can set over-temp alarms etc).

Farnell and RS are big electronics suppliers in the UK that have a range of similar meters that are basically a small box with a display on the front that you can connect the thermocouple leads directly to and power from the PC's 12V supply. See this one and this one which both read down to -50C.

The alternative is simply to stick with the multimeter, or butcher a multimeter (or a multimeter style temp meter) so you can mount it in the PC or cooler case.

Note that there's no easy way, short of writing plugin code and interfacing the temp meter to the PC somehow (serial port?), to get the temp info displayed on the sort of LCD system that the Smartie software controls.

Matt.

_X7JAY7X_ · Post by **_X7JAY7X_** » January 8th, 2007, 5:11 pm

Your correct mattcro. The max6675 doesnt do negative (I goofed), but I believe the AD594/595 does. However this requires an external ADC.

If you want to go the panel meter route and install it in your computer I would check ebay. You should be able to find something older and cheaper on there.

J