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PICList Thread
'Sensors'
1995\10\31@124417 by Mark D. Herold

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Hello,
I am presently designing a magnetic sensor device using the PIC16C71 as the
controller for the project. What I am looking for is a linear output
Hall effect sensor. In the past I've used Allegro Inc. for these parts but
presently they are sold out! Any sources that you are aware of will be
considered. Other magnetic sensor types will also be considered. As is typical,
cost is an issue. To save bandwidth please drop replies to my Email address.

If anyone has run across a list or net site that focuses on sensors I would
also like to know about them.

Thanks in advance.

Mark Herold Email: spam_OUTheroldTakeThisOuTspamresearch.bfg.com

1995\10\31@135419 by Ed Gilchrest

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Try Honeywell / Microswitch...
They make a line of linear output hall effect and magnetoresistive devices

Hope that helps


'Sensors'
1995\11\05@124830 by Bill Cornutt
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----------
>Hello,
>I am presently designing a magnetic sensor device using the PIC16C71 as the
>controller for the project. What I am looking for is a linear output
>Hall effect sensor. In the past I've used Allegro Inc. for these parts but
>presently they are sold out! Any sources that you are aware of will be
>considered. Other magnetic sensor types will also be considered. As is typical,
>cost is an issue. To save bandwidth please drop replies to my Email address.
>
>If anyone has run across a list or net site that focuses on sensors I would
>also like to know about them.
>
>Thanks in advance.
>
>Mark Herold Email: .....heroldKILLspamspam@spam@research.bfg.com
>

Whereas the world is Analog, it is also true that it is non Linear.

So a linear device may be a proublem.  A way around this is to
plot the output of the device vs input and derive a formula that
reflects this.  Then use the formula in a pc program to generate
'data' statements to put in the pic program.  I think the 'load
w reg and return from subroutine' instruction could be used as a
table lookup.  As this would take 256 instructions, perhaps it
would be better to have a sixteen byte lookup table for the high
nibble of the value and then a table with the 'interperalation'
for the low nibble of each value of high nibble.  It may be
necessary to have the low nibble table contain a mixed value.
that is a value in which the bits do not represent one, but represent
1/2 or 1/4 or 1/8 of the value.  With this it would be possible to
have the interpralation be 3/8 at points where the change per unit
input does is less than one.

A word of advice, if you do this, don't loose the formula.  You
may need it latter for something.

All that said, how expensive is a magnetic pickup for a guitar?

  ---------
  Bill Cornutt
  billcornspamKILLspaminfoserv.com
  Located in Ione California USA.
  A small town in Northern California.
  Sitting against the foothills of the Mother Lode.
  ----------------------------------------------------


'Sensors'
1997\02\28@062822 by David BALDWIN
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Wolfgang,

       What kind of temperature and humidity sensors are you using? Is it
possible to get your code to drive the temp. sensor if it a DS1820 and
the EEPROM? Thanks.

--

 _____________
 \           /               David BALDWIN
  \ ALCATEL /               Design engineer
   \TELECOM/
    \     /         SdM (Societe de Microelectronique)
     \   /
      \ /      B.P. 4205            Phone : +32 (0)71 442932
       V       B-6000 Charleroi     Fax   : +32 (0)71 442905
               (Belgium)            .....baldwinKILLspamspam.....etca.alcatel.be


'Sensors'
1998\09\30@081816 by Neil Calitz
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Hi all

I am looking for sensors for a project that I am working on.

1.  What I need is Temprature sensors (up to 1000 deg Celcius)
2.  Presure sensors.
3.  Directional (like a compas)
4.  Someting to act as a Altimeter.

Please help

Niel Calitz


'Sensors'
1998\10\01@001520 by Russell McMahon
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Temperature:    For such a high temperature a thermocouple is
(probably) the most sensible choice. Depending on requirements a
'Pyrometer" may be justified - measures wavelength of radiated infra
red. Thermocouples are MUCH cheaper. Even the common "Type K"
thermocouples sold in most electronics stores will work to over 1300
Celsius. The "sensor" is Nickel-Chromium/Nickel-Aluminium wire and is
potentially very cheap. Designs for thermocouple amplifiers are
available from various semiconductor makers.

Pressure  /Direction / Altimeter:    Look at the archives of recent
PICLIST discussions. There have been various mentions of all these in
the past few months. Someone here will be able to tell you how to
access the archives.
.
.
-----Original Message-----
From: Neil Calitz <EraseMEncalitzspam_OUTspamTakeThisOuTOLDMUTUAL.COM>
>I am looking for sensors for a project that I am working on.
>
>1.  What I need is Temprature sensors (up to 1000 deg Celcius)
>2.  Presure sensors.
>3.  Directional (like a compas)
>4.  Someting to act as a Altimeter.

1998\10\01@071206 by Nicholas Irias

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For the temp sensor, you probably want a nickel-chrome to nickel aluminum
thermo couple.  The cost of these arises not so much from the wire junction,
but the housing that is used to protect the lead wires and the junction
itself from physical damage.  I use one of these thermocouples to measure
the temp of molten aluminum, and the sensor I use is in a 3 foot long
protective tube to keep the aluminum off the wires - cost around $90.  If
you have a more controlled environment (maybe not immersing in a molten
metal or other corrosive material) so that you do not need such a large
protective housing, the thermocouple will be cheaper.

To use a thermocouple you need a rating curve in mV/degree.  But note that
1) at some point the thermocouple wires will transistion to copper wire, and
2) your reading of mV from the copper leads, when translated to degrees C,
is actually the difference in junction temperatures.

Unless the nickel alloy to copper junction temp will be constant, you will
want to monitor that secondary junction with something like a DS1620 located
at that junction.  You can then compare that secondary junction temp to the
temp at which the thermocouple rating curve was developed.  If the
thermocouple was calibrated with the secondary junction at 0 degrees (in an
icewater bath), and your secondary junction temp is measured as 25 degrees
C, just add the 25 degrees C to the temp reading you get from the
thermocouple's calibration curve.

You may need an amplifier.  These junctions can be read easily with a DVM,
but I havent tried reading with a PIC A/D, which wants a relatively low
source impedance.

Don't have any info for the other sensors.  What are you building anyway, a
Venus probe or some other sort of re-entry vehicle?

-Nicholas

-----Original Message-----
From: Neil Calitz <ncalitzspamspam_OUTOLDMUTUAL.COM>
To: @spam@PICLISTKILLspamspamMITVMA.MIT.EDU <KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU>
Date: Wednesday, September 30, 1998 5:21 AM
Subject: Sensors


{Quote hidden}

1998\10\02@081636 by paulb

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Nicholas Irias wrote:

> You may need an amplifier.  These junctions can be read easily with a
> DVM, but I havent tried reading with a PIC A/D, which wants a
> relatively low source impedance.

 I wouldn«t worry too much about that.  You can«t *get* much lower
impedance than a thermocouple!  The safety switch in a gas room heater
consists of a thermocouple powering a solenoid.  The solenoid has very
few turns!
--
 Cheers,
       Paul B.

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