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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Tue, 22 Jul 1997 00:13:13 GMT
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Original-From:
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Brian Lavery <BLAVERY@ACSLINK.AONE.NET.AUihatespam>
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Viewed:
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1201 times
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Jeff,
I used a couple of the 10mV/deg Kelvin ones, with nothing more than the
current load resistor, ie no amplification at all. For example, freezing
point = zero celcius = 273 Kelvin = 2.73 volts. With the 6811 resolution of
about 20 mV (5v / 256), that meant I could only read to 2 degrees accuracy.
But I had one in free air, and one strapped to the battery pack, so I could
read the temperature rise above ambient as the battery charged (esp in ZAP
mode). A simplistic program rang the beeper when the battery was full
(several degrees temperature differential). So sometimes fine accuracy is
not really needed!
Brian
At 16:58 20/07/97 -0700, you 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/
>
>
>
Brian Lavery
37 Kulgoa Road
Pymble 2073
02-93709250 BH
<BLAVERY@ACSLINK.AONE.NET.AU>
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