Cheap Temp Recording

Hey all. I had a guy ask me today about how he could record 4 temps periodically to PC on the cheap. Ie, Very Cheap. Being used to working with thermocouples, nothing ive found sofar qualifies as super cheap (his budget is around 80 - 100 dollars). This is for a yeast freezing experiment he is doing. I thought of things like splatco's little micro plcs using thermistors but they still come out pushing 300 dollars before attaching to serial. Any thoughts or such? This doesnt need to be in any way industrial. I believe after 3 or runs with the system it will be retired. Thanks in advance.

Matt

Cheap temp recording

How good are you with electronics and programming?

A PC based temp recording can be made out of a thermistor and a few resistors fed into the joystick port on a PC. Then a program can be written to capture the data.

All for about $5 if you have a PC with a joystick port. A lot of sound cards have joystick ports.

Here is something similar:

http://www.hilaroad.com/camp/projects/vb_jstick.html

Thats sound very interesting! Ill have to check it out. I even have about 12 sound cards laying around. Can it do multiple inputs? Wonder if a serial port can do that as well. Ill follow that link. I dont know about the guy that asked me, but I have plenty of computer skills from VB to C to PLCs.

Anything else?

A joystick port has 4 analog inputs. Here is the pinout:

http://www.interfacebus.com/PC_Joy_Stick_Pinout.html


I noticed the mabry link for the activeX control no longer worked, but here is one of many more out there:

http://www.codeproject.com/cs/media/joystick.asp?df=100&forumid=365812&exp=0

I would look into a PIC micro. The PIC16F88 has 7-10bit analog channels and can interface to a RS232 sreial driver very easily.
I would run thermistors on the analog channels and just send out the temp values through the 232 driver. Over all you should be able to build the whole project for under $100.




Dave

any good sources for thermistors besides omega? I tried mouser but they dont seem to have probe / encapsulated ones. Thanks.

You may want to check into some of the kits used by garden plant people. I saw one last year, you stuck it in the soil and it measured temp and humidity. After 24 hours or so, you hooked it up to your computer and downloaded the results thru the serial port.

It was very low cost and if I find the link, I will post it here.

http://www.microdaq.com/data-logger/temperature/1.php

See these guys - http://www.measurementcomputing.com/ for a selection of cheap measuring and data logging devices you can plug into your USB port.