LM34 and the Basic Stamp 2.5

kovachjm

What is the best way to use the temperature sensor LM34 for the Basic Stamp 2.5. I do not have an ADC chip; can I use the RCtime command? What would the RC circuit look like attached to the LM34 leads?

Sapphire

You cannot use RC time to read the LM34 temp. It requires an ADC, or at least a comparator configured to function as an ADC which you drive with the stamp.

bsjohn

Well the most elegant way is with a ADC because the lm34 outputs in increments of 10mv/F degree but lacking that I found these articles which should suite you well:
http://www.societyofrobots.com/robotforum/index.php?topic=8776.0
http://www.noisemantra.com/BASICStampAnalogInput.htm
I've never tried these so your results may vary.

kovachjm

Thank you for the replies. I ended up just borrowing an Arduino from a friend to use.

-bsjohn, Thanks for the articles, the second one seems to make a lot of sense. I am going to finish my project with an Arduino. But, after I finish it I will return to the BS2 and try to see if I can modify the circuit in the second article for my use.

Thanks

davejames

kovachjm - hope that you come back from the "dark side" soon!

BTW, I changed your original post to indicate "solved".

Tracy Allen

That's funny, the societyofrobots link is a verbatim but unattributed copy of my article at http://emesystems.com/BS2rct.htm#B_voltage.

Neither that nor the noisemantra articles are good ways to deal with the LM34.

If you really want to use the LM34 in an RCtime circuit, look at the figure in the LM34 data sheet under the caption, "Two-Wire Remote Temperature Sensor (Output Referred to Ground)". That turns the LM34 into a linear current source of 20µA/°F that can charge the RCTIME capacitor at a rate directly proportional to temperature. You would replace the 50kΩ rheostat shown in that schematic with a stable capacitor, say 0.01µF.