Monday, December 17, 2007

Thermocouple continued

Didn't do much today, had other things to do.

Did find out that int(variable) will convert a float variable to int. That is change 58.93929399234 to 58. So simple.

I had thought about a decoupling capacitor to fix my fluctuating readings problem. Didn't do anything until Pete mentioned I should try it. Found a couple links. One is about decoupling capacitors in general and sounds pretty reasonable. And another that shows one in schematic with a AD595 in use. It is a page on using the AD595 thermocouple IC with a Basic Stamp.

I tried values from .01uF to 1uf between the +5V input and ground, and as far as I can tell it doesn't make any difference. I tried smoothing the output by putting a .04uF capacitor there and that cut the fluctuation down by half. At this point I don't think I am going to do anything until I can find something that really works, and I know why. It works well enough and for what I need it for a plus/minus a degree is not important. Maybee it is normal. I don't think so though.

I went back to take another look at the k type thermocouple. It reads 0 volts, not too good. I tried the other K type I have and though it does read, the serial output reads very erratic. The data from the serial monitor looks like this:
61
0
0
0
0
61
0
0
0
0
63
0
0
0
0
Etc.
This does not make me happy!


The emesys.com site has a lot of Basic Stamp application stuff.

I might try the max digital thermocouple ic.

I am going to think about this one a bit and do some more research.

1 comment:

Pete said...

I found a project page from Hackaday.com that uses a K type TC and he used a moving average to smooth out the fluctuation in temperature readings. Basically he added the temp readings for like 10,000 readings and then divided by 10,000. The result was a temperature reading given about once per second. He didn't share the code from what I could see, but the concept seems very applicable to controlling the temperature on the BBQ or whatnot. Here's the link: http://www.blog.nashlincoln.com/espresso/gaggia-espresso-pid-arduino-mod