Searching \ for '[EE]: LM35 Woes' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=lm35+woes
Search entire site for: 'LM35 Woes'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: LM35 Woes'
2001\07\24@234938 by Nick Veys

flavicon
face
Greetings :)  I'm having trouble with some LM35 Centigrade temperature
sensors... I'm simply trying to read them w/a multimeter and getting
annoying values.  The Vss and Gnd are 5.12 and 0 respectively, and when
I go to read the Vout, I get between .667 - .733 V.  Meaning my room is
a toasty 66.7-73.3C.  Quite warm!  This is happening with 3 separate
sensors!  Not sure what my problem is...  Any tips?  Perhaps I'm reading
this totally wrong?

spam_OUTnickTakeThisOuTspamveys.com | http://www.veys.com/nick

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email .....listservKILLspamspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body


2001\07\25@021534 by hard Prosser

flavicon
face
Try connecting them the other way around
(when connected backward they look like a diode)

Richard P



Greetings :)  I'm having trouble with some LM35 Centigrade temperature
sensors... I'm simply trying to read them w/a multimeter and getting
annoying values.  The Vss and Gnd are 5.12 and 0 respectively, and when
I go to read the Vout, I get between .667 - .733 V.  Meaning my room is
a toasty 66.7-73.3C.  Quite warm!  This is happening with 3 separate
sensors!  Not sure what my problem is...  Any tips?  Perhaps I'm reading
this totally wrong?

nickspamKILLspamveys.com | http://www.veys.com/nick

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email .....listservKILLspamspam.....mitvma.mit.edu with SET PICList DIGEST in the body

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspam_OUTspamTakeThisOuTmitvma.mit.edu


2001\07\25@023916 by Spehro Pefhany

picon face
At 09:40 PM 7/24/01 -0500, you wrote:
>Greetings :)  I'm having trouble with some LM35 Centigrade temperature
>sensors... I'm simply trying to read them w/a multimeter and getting
>annoying values.  The Vss and Gnd are 5.12 and 0 respectively, and when
>I go to read the Vout, I get between .667 - .733 V.  Meaning my room is
>a toasty 66.7-73.3C.  Quite warm!  This is happening with 3 separate
>sensors!  Not sure what my problem is...  Any tips?  Perhaps I'm reading
>this totally wrong?

Is it possible you have reversed +Vs (not Vss) and Gnd?  Note that the
data sheet (you *do* have the actual data sheet?) shows the connections
from the bottom, not looking down through the top as is sometimes
done.

That number is suspiciously close to one diode drop.

Best regards,



=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestKILLspamspammitvma.mit.edu


2001\07\25@023939 by Wade Carpenter

picon face
Hi Nick,

I think if you refer to the app. notes in the data sheet, it will give you a
suggested circuit to use the device in it's proper operating mode; this may
be the problem.  I am using the LM34 (Farenheit sensor) and it works quite
well.

Hope that helps.

- Wade

{Original Message removed}

2001\07\25@024447 by Mike Kendall

flavicon
face
Nick,
   My only experience with sensors is for pressure type.  In my experience
there was a circuit that sensed a depth and there were precision resistors
that would set the minimum depth and the other would set the span.  I looked
in the "programming and customizing microcontrollers" book I'm reading and
the digital thermometer experiment.  Based on this and  my experience with
thermistors in sonars, there is usually an external circuit to calibrate the
variations in actual components.  Also, I'd be curious to know if  the
measured voltage with  a DMM (usually around 10megaohms/volt sensitivity) is
supposed to be the same as the in-circuit voltage of your device which
surely would have a higher current drain? The PICmicro book warns about the
thermistor being too close to a warm microcontroller also.
Regards,
Mike/ke6cvh

{Original Message removed}

2001\07\25@074448 by Vasile Surducan

flavicon
face
As you write is almost sure you've polarised in reversed way the sensor.
It's no big deal, reverse again the Vcc with Gnd and you'll have about
2.7315V at 0C with 10mV increases every Celsius degree.
Leave the adjusting pin open without any potentiometer conected to this
pin.
Vasile

On Tue, 24 Jul 2001, Nick Veys wrote:

{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
spamBeGonepiclist-unsubscribe-requestspamBeGonespammitvma.mit.edu


2001\07\25@080338 by Rodrigo Valladares P.

picon face
Your sensors are ok, the temperature range is -55 to +150 centigrade
degrees, and the slope is 10.0 mV/Deg, starting at 0V = -55 deg:

0V is -55 deg.
0.70V is 15 deg.
2.1V is 155 deg.

this makes sense ?  :)






----- Mensaje original -----
De: "Nick Veys" <TakeThisOuTnickEraseMEspamspam_OUTVEYS.COM>
Para: <RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU>
Enviado: Martes 24 de Julio de 2001 10:40 PM
Asunto: [EE]: LM35 Woes


{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestEraseMEspamEraseMEmitvma.mit.edu


2001\07\25@082240 by Rodrigo Valladares P.

picon face
Your sensors are ok, the temperature range is -55 to +150 centigrade
degrees, and the slope is 10.0 mV/Deg, starting at 0V = -55 deg:

0V is -55 deg.
0.70V is 15 deg.
2.1V is 155 deg.

this makes sense ?  :)






----- Mensaje original -----
De: "Nick Veys" <RemoveMEnickspam_OUTspamKILLspamVEYS.COM>
Para: <RemoveMEPICLISTTakeThisOuTspamspamMITVMA.MIT.EDU>
Enviado: Martes 24 de Julio de 2001 10:40 PM
Asunto: [EE]: LM35 Woes


> Greetings :)  I'm having trouble with some LM35 Centigrade temperature
> sensors... I'm simply trying to read them w/a multimeter and getting
> annoying values.  The Vss and Gnd are 5.12 and 0 respectively, and when
> I go to read the Vout, I get between .667 - .733 V.  Meaning my room is
> a toasty 66.7-73.3C.  Quite warm!  This is happening with 3 separate
> sensors!  Not sure what my problem is...  Any tips?  Perhaps I'm reading
> this totally wrong?
>
> EraseMEnickspamspamspamBeGoneveys.com | http://www.veys.com/nick
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> email RemoveMElistservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body
>
>
>

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestSTOPspamspamspam_OUTmitvma.mit.edu


2001\07\25@101100 by Nick Veys

flavicon
face
First thing I tried... It promptly heated up way beyond being
touchable...

spamBeGonenickSTOPspamspamEraseMEveys.com | http://www.veys.com/nick


> {Original Message removed}

2001\07\25@101649 by Nick Veys

flavicon
face
I'm using the "Basic Centigrade Temperature Sensor".  It's output is 0mV
+ 10mV/C, and it's extremely simple, just power and ground, and output.

KILLspamnickspamBeGonespamveys.com | http://www.veys.com/nick


> {Original Message removed}

2001\07\25@101702 by Nick Veys

flavicon
face
Are you sure?  I'm using the LM35D which is 0-100C on the datasheet...
And the basic circuit I'm using shows output = 0mV + 10mV/C so 0C should
be 0V I would assume!

Is it possible these devices are super sensitive to heat and died when
soldering?

EraseMEnickspamEraseMEveys.com | http://www.veys.com/nick


> {Original Message removed}

2001\07\25@104927 by Herbert Graf

flavicon
face
I think you are thinking of the LM50? IIRC the LM35 outputs 0V at 0 degrees
C and -0.55V at -55 Degrees C. TTYL

> {Original Message removed}

2001\07\25@104951 by Spehro Pefhany

picon face
At 08:12 AM 7/25/01 -0500, you wrote:
>First thing I tried... It promptly heated up way beyond being
>touchable...

Ok, well, you don't happen to have a capacitor connected to the
output do you?  Or a long cable?

Like most voltage-output devices, these things are senstive to
capacitive loading and will oscillate away causing all kinds of
strange readings on a DVM.

Best regards,
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
@spam@speff@spam@spamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: To leave the PICList
spamBeGonepiclist-unsubscribe-requestspamKILLspammitvma.mit.edu


2001\07\25@105811 by t F. Touchton

flavicon
face
part 1 2244 bytes content-type:text/plain; charset=us-ascii
If all you connections check out (including placing a loading R on the
output... 10K or so) they might in reality be the Fahrenheit version......

Scott F. Touchton
1550 Engineering Manager
JDS Uniphase



                   Nick Veys
                   <.....nickspam_OUTspamVEYS.COM        To:     TakeThisOuTPICLIST.....spamTakeThisOuTMITVMA.MIT.EDU
                   >                     cc:
                   Sent by: pic          Subject:     Re: [EE]: LM35 Woes
                   microcontrolle
                   r discussion
                   list
                   <PICLIST@MITVM
                   A.MIT.EDU>


                   07/25/01 09:12
                   AM
                   Please respond
                   to pic
                   microcontrolle
                   r discussion
                   list






First thing I tried... It promptly heated up way beyond being
touchable...

TakeThisOuTnickKILLspamspamspamveys.com | http://www.veys.com/nick


> {Original Message removed}
part 2 3762 bytes content-type:application/octet-stream; (decode)

part 3 105 bytes
--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestspamRemoveMEmitvma.mit.edu


2001\07\25@131631 by Nick Veys

flavicon
face
Glancing at the datasheet I don't see anything for a loading resistor so
I didn't use one... I'll give that a try.

RemoveMEnickspamspamBeGoneveys.com | http://www.veys.com/nick


> {Original Message removed}

2001\07\25@133334 by Mike Kendall

flavicon
face
If a loading resistor of 10kohm is needed for the circuit, and you are
using a digital multimeter with a sensitivity of 10mohm/volt, you should be
able to substitute the measurement with an older analog meter such as a
Simpson 260 that has a sensitivity of 10kohm/volt and would be ideal for
checking the accuracy of the sensor out of circuit without any loading
resistor (the meter would be your loading resistor).  Maybe this is what
the manufacturer does during the QA process of the component anyways?
Mike/ke6cvh
----- Original Message -----
From: Nick Veys <spamBeGonenick@spam@spamspam_OUTVEYS.COM>
Sent: Wednesday, July 25, 2001 12:13:19 PM
To: <TakeThisOuTPICLISTspamspamMITVMA.MIT.EDU>
Subject: Re: [EE]: LM35 Woes

> Glancing at the datasheet I don't see anything for a loading resistor so
> I didn't use one... I'll give that a try.
>
> nickEraseMEspamveys.com | http://www.veys.com/nick
>
>
> > {Original Message removed}

2001\07\25@135043 by Barry Gershenfeld

picon face
Those would be good temperatures if you were in Fahrenheit.  Maybe
the package is mislabelled?

Does it change when you touch (warm) it?

>Greetings :)  I'm having trouble with some LM35 Centigrade temperature
>sensors... I'm simply trying to read them w/a multimeter and getting
>annoying values.  The Vss and Gnd are 5.12 and 0 respectively, and when
>I go to read the Vout, I get between .667 - .733 V.  Meaning my room is
>a toasty 66.7-73.3C.  Quite warm!  This is happening with 3 separate
>sensors!  Not sure what my problem is...  Any tips?  Perhaps I'm reading
>this totally wrong?
>
>RemoveMEnickEraseMEspamspam_OUTveys.com | http://www.veys.com/nick

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-requestRemoveMEspamEraseMEmitvma.mit.edu


2001\07\25@213437 by Wade Carpenter

picon face
Yeah, it is the same one I was using (just today I put the circuit together)
and was getting out 10mV/degree, and the negative temperatures are taken
care of with negative voltage.  You don't have to scale anything, so I think
there must be something wrong.  But I have noticed that, in general, it
seems to read a little on the hot side.  I was getting about 80 F and it
didn't feel that warm in the office =)

But I don't think it should be THAT far out, like 70 C!

I just put an RC filter on the output pin, and I'm powering it from +5V to
GND.  I can't really say what the problem might be.  Maybe your output
circuit (or voltmeter) is loading the chip?

- Wade
----- Original Message -----
From: "Nick Veys" <EraseMEnickspam@spam@VEYS.COM>
To: <@spam@PICLISTspam_OUTspam.....MITVMA.MIT.EDU>
Sent: Wednesday, July 25, 2001 6:20 AM
Subject: Re: [EE]: LM35 Woes


> I'm using the "Basic Centigrade Temperature Sensor".  It's output is 0mV
> + 10mV/C, and it's extremely simple, just power and ground, and output.
>
> spamBeGonenickEraseMEspamveys.com | http://www.veys.com/nick
>
>
> > {Original Message removed}

2001\07\25@220304 by Nick Veys

flavicon
face
Well I think I got it... I put a 10k resistor between Vout and Gnd, and
it seems to like that, I'm getting output voltages in the area of .33
now, MUCH more like it! :)  Now I just need to figure out some good
multiplication and division routines to convert my A/D readings... One
problem after the other!  I assume there are some in the piclist
archives though...

nickspamBeGonespamveys.com | http://www.veys.com/nick


> {Original Message removed}

2001\07\25@224222 by Tom Handley

picon face
  Rodrigo, the LM35 outputs 10mV/deg C where 0 deg C = 0mV, -1 deg = -10mV,
+1 deg = +10mV, etc. So 667mV = 66.7 deg C. It really sounds like Nick is
using an LM34 which would give 66.7 deg F...

  - Tom

At 02:05 AM 7/25/01 -0400, Rodrigo Valladares P wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

--
http://www.piclist.com hint: To leave the PICList
.....piclist-unsubscribe-requestSTOPspamspam@spam@mitvma.mit.edu


2001\07\25@225506 by Spehro Pefhany

picon face
At 07:42 PM 7/25/01 -0700, you wrote:
>   Rodrigo, the LM35 outputs 10mV/deg C where 0 deg C = 0mV, -1 deg = -10mV,
>+1 deg = +10mV, etc. So 667mV = 66.7 deg C. It really sounds like Nick is
>using an LM34 which would give 66.7 deg F...

Sounds like he may have connected a resistor (or had leakage or bias current)
from the output to Vcc, which  may have overwhelmed the internal resistors
(it's a common-emitter output, so it can only source significant current, not
sink it). Even a couple of dozen microamps could do that- it would cause the
temperature vs. voltage curve to plateau at some value, and the exact
temperature at which it stopped working properly would be quite variable
from unit to unit because of the wide variation in IC resistor values.

Best regards,
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffEraseMEspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestspamspamBeGonemitvma.mit.edu


2001\07\25@231430 by Tom Handley

picon face
  Nick, I've used the LM35's `Fahrenheit cousin' the LM34 for years with
wiring runs up to 300ft. The first thing I noticed is your output range;
667 - 733mv. If you were using an LM34 that would be 66.7 - 73.3 deg F.
Are you sure that's an LM35?

  The other thing, and this is very important, you need to install the
bypass cap, the R-C Damper, and the 2K resistor to isolate line/load
capacitance.

  I normally mount the bypass cap and R-C damper network right at the
sensor. At the other end on the input of the A/D, I use a 2K resistor,
followed by a 0.01uf cap.

  - Tom

At 09:40 PM 7/24/01 -0500, Nick Veys wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspam_OUTspam@spam@mitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...