Subject:
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Re: 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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Mon, 21 Jul 1997 01:00:22 GMT
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Original-From:
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Colin A. Reed <aleph@cco./nomorespam/caltech.edu>
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Viewed:
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644 times
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It sounds like you just want a standard non-inverting amplifier. wire an
op amp like this:
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sensor------|+\
| >-+-analog input of 6811
+--|-/ |
| |/ |
+----R1-+
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R
2
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GND
where R1 and R2 are chosen such that (R1+R2)/R2 is the gain you want, in
this case, a little over 2. The current drive of the sensor doesn't really
matter as op-amps have very high input impedence. Since you aren't driving
a high power device like a speaker, and you're not looking at high
frequency stuff, you should be able to use just about any op-amp. The
TL074 is a cheap, standard dual op-amp package that you might want to use.
The one problem with op-amps is that they are usually designed to be
supplied with +15 and -15 volts. Since you are only interested in seeing
an output swing of 0-5 volts, you can probably use those as the input
rails, but you might get some nonlinearities close to the rails. Hope this
covers all your questions.
-Colin
At 04:58 PM 7/20/97 -0700, Jeff Keyzer wrote:
> 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 is in Reply To:
 | | LM34 temp sensor to handy board?
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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 (...) (27 years ago, 20-Jul-97, to lugnet.robotics.handyboard)
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