Subject:
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LM34 temp sensor to handy board?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sun, 20 Jul 1997 23:58:59 GMT
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Original-From:
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Jeff Keyzer <jkeyzer@ucsd.eduNOMORESPAM>
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Viewed:
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648 times
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I've got on my desk here a National Semiconductor LM34 temperature sensor.
It outputs a voltage corresponding to 10mV/deg F. So, if it's 78 degrees
F in the room, I get a voltage of .78V. I'd like to hook this device to an
analog port on my handy board. However, the handy board takes an input
voltage between 0 and 5V, while the sensor is only going to reach around
1.15 volts on a really, really hot California day. I'd like to somehow
scale this voltage up so that I get increased resolution on the HB's analog
input, causing a voltage of, say, 1.28V to become 5V. (Then I could divide
the analog value by two to get the actual temp.) The voltage amplification
must be roughly linear, or my temperature readings will be horribly
inaccurate. I was thinking perhaps an op-amp or transistor amplifier might
do the job, but my experience with such devices is very limited, and my
references here haven't done me much good. Does anyone have any experience
with the LM34 sensor, or any ideas as to how I could make this work?
(PS, the LM34 sensor has an absolute max. output current of 10mA.)
--------------------------------
Jeff Keyzer
UCSD EE Major
jkeyzer@ucsd.edu
http://sehplib.ucsd.edu/~jkeyzer/
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Message has 2 Replies:
 | | Re: LM34 temp sensor to handy board?
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| It sounds like you just want a standard non-inverting amplifier. wire an op amp like this: |\ sensor------|+\ | >-+-analog input of 6811 +--|-/ | | |/ | +----R1-+ | R 2 | GND where R1 and R2 are chosen such that (R1+R2)/R2 is the gain you want, in (...) (27 years ago, 21-Jul-97, to lugnet.robotics.handyboard)
| | | Re: LM34 temp sensor to handy board?
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| I tried the circuit out tonight, and it works! (Mostly.) I hooked up a 1K and a 3K resistor for R2 and R1, for a gain of 4, and the output is roughly linear with the input. Still need to do some more testing. I ended up having to use a +/- 12V (...) (27 years ago, 21-Jul-97, to lugnet.robotics.handyboard)
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