Getting started: Thermistor and LM34

Jeff M

It has been years since I played with my Basic Stamp 2, but I have a project it would be perfect for and I need some help getting started.

The project will involve monitoring the temperature of both water (30deg F - 40deg F) and air (40deg F to 110deg F).

I have ordered some LM34s but as I'm waiting for delivery, I found some Radio Shack 10k-Ohm Thermistors 271-110A.

My research of the site has lead me to http://www.parallax.com/Portals/0/Downloads/appnt/stamps/bs1Appnotes.pdf page 33 (using a thermistor) and I wanted to give it a go.

I loaded the code into the editor, but I get a syntax error
"Expected ':' or end-of-line"

at this point
"Symbol co0 = 162"

I'm guessing this has to do with this code being for a BS1 and not a BS2, but I'm having trouble figuring out what is causing it.

Thanks in advance for the help.
JM

Shawn Lowe

Yes, symbol is only used on the BS1. Maybe post all your code and we can help further

Shawn Lowe

Nevermind found it:

' Program THERM.BAS
' This program reads a thermistor with the BASIC
' pot command, computes the temperature using a
' power-series polynomial equation, and reports
' the result to a host PC via the Stamp cable
' using the debug command.
' Symbol constants represent factored portions of
' the coefficients C0, C1, and C2. "Top" and "btm"
' refer to the values' positions in the fractions;
' on top as a multiplier or on the bottom as a
' divisor.
Symbol co0 = 162
Symbol co1top = 255
Symbol co1btm = 2125
Symbol co2bt1 = 25
Symbol co2top = 3
Symbol co2btm = 50
' Program loop.
Check_temp:
pot 0,46,w0 ' 46 is the scale factor.
' Remember that Stamp math is computed left to
' right--no parentheses, no precedence of
' operators.
let w1 = w0*w0/co2bt1*co2top/co2btm
let w0 = w0*co1top/co1btm+w0
let w0 = co0+w1-w0
debug w0
pause 1000 ' Wait 1 second for next
goto Check_temp ' temperature reading.

Sorry for no code brackets, cant find the button. Now i'm the new guy! lol

Jeff M

Thanks for the help.

I removed the keyword Symbol but I get the same error.

Jeff M

I managed to get the code to pass by chaing pot to RCTIME and removing the 'let':

co0 VAR Word
co0 = 162

co1top VAR Word
co1top = 255

co1btm VAR Word
co1btm = 2125

co2bt1 VAR Word
co2bt1 = 25

co2top VAR Word
co2top = 3

co2btm VAR Word
co2btm = 50


' Program loop.
Check_temp:
RCTIME 0,46,W0 ' 46 is the scale factor.
' Remember that Stamp math is computed left to
' right--no parentheses, no precedence of
' operators.
W1 = W0*W0/co2bt1*co2top/co2btm
W0 = W0*co1top/co1btm+W0
W0 = co0+W1-W0
DEBUG W0
PAUSE 1000 ' Wait 1 second for next
GOTO Check_temp ' temperature reading.

and found the [ code ] [ / code ] tags

Shawn Lowe

Cool, looks like you're ready to play. Where did you find the code tags?

Jeff M

Shawn Lowe wrote: »

Cool, looks like you're ready to play. Where did you find the code tags?

Not sure how I found it, but the BB code is listed here:
http://forums.parallax.com/misc.php?do=bbcode#code

Shawn Lowe

Oh, okay thanks!

Jeff M

Update:

I got the code to output some data to the debug window by adding 'DEBUG DEC W0' the DEC was missing.

Now all I get are 000000 in the window.

Any thoughts on how to figure out what is going on?

' {$STAMP BS2}
' {$PBASIC 2.0}
' Program THERM.BAS
' This program reads a thermistor with the BASIC
' pot command, computes the temperature using a
' power-series polynomial equation, and reports
' the result to a host PC via the Stamp cable
' using the debug command.
' Symbol constants represent factored portions of
' the coefficients C0, C1, and C2. "Top" and "btm"
' refer to the values' positions in the fractions;
' on top as a multiplier or on the bottom as a
' divisor.

co0 VAR Word
co0 = 162

co1top VAR Word
co1top = 255

co1btm VAR Word
co1btm = 2125

co2bt1 VAR Word
co2bt1 = 25

co2top VAR Word
co2top = 3

co2btm VAR Word
co2btm = 50

' Program loop.
Check_temp:
RCTIME 1,46,W0 ' 46 is the scale factor.
' Remember that Stamp math is computed left to
' right--no parentheses, no precedence of
' operators.
W1 = W0*W0/co2bt1*co2top/co2btm
W0 = W0*co1top/co1btm+W0
W0 = co0+W1-W0
'DEBUG W0
PAUSE 1000
DEBUG DEC W0
PAUSE 1000 ' Wait 1 second for next
GOTO Check_temp ' temperature reading.

Shawn Lowe

are you sure you have your thermistor hooked to pin 1?

Jeff M

yea i found it was wired wrong.. yet i have seen several different ways to connect it.
I'm a bit confused on what wiring to use, and then there is the math to convert the output to temp....
I could use a good example that someone knows works on the BS2.