Getting started: Thermistor and LM34

Jeff M · 2012-04-03 09:08

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 · 2012-04-03 09:23

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

Shawn Lowe · 2012-04-03 09:30

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 · 2012-04-03 09:34

Thanks for the help.

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

Jeff M · 2012-04-03 09:44

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 · 2012-04-03 09:54

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

Jeff M · 2012-04-03 10:17

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 · 2012-04-03 13:22

Oh, okay thanks!

Jeff M · 2012-04-04 18:53

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 · 2012-04-05 12:04

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

Jeff M · 2012-04-06 19:41

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.

Getting started: Thermistor and LM34

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