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'New Design:temperature controller'
1996\06\06@103234 by Harrison Cooper

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Latest thing to hit me is a temperature controller.  What I'm replacing (this is
real
disgusting) is an embedded PC, using a STD CPU card, a A/D and digital output
card, plus
a STD rack.  Its only job is to keep a heatsink at a set temperature.  Long
story why it
was done originally like this....

OK, so I need to monitor two temperature sensors - one on the heatsink, one away
from it
(free air temp).  Two choices - analog or digital.  Anyone had much experiance
with the
new breed of parts, like the ones from Dallas or Analog Devices ?  I'd rather d
stay in the digital domain.

Setpoints and storage - I need a simple RS232 type interface with a PC to send
down the
desired setpoint and to read back the two temperatures.  Storage of at least the
setpoint
in nonvolatile memory is required.  Choice here is either eeprom or batt backed
sram such
as the parts from Simtek (battery built inside the sram).

OK, the '84 gives me EEPROM, so thats nice.  No built-in UART. Has anyone does
RS232 comm
with a PC an a '84 ?  I've never needed to implement a serial comm link.  The
'84 would
work fine if I used a digital part.  Otherwise, the '71 could be used, but then
I need to
add a current source and amp section.  Either could accomadate the control loop.

Comments anyone ?
spam_OUThcooperTakeThisOuTspames.com

1996\06\06@110747 by Wireless Scientific

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At 8:32 AM 6/6/96, Harrison Cooper wrote:
>new breed of parts, like the ones from Dallas or Analog Devices ?  I'd rather d
>stay in the digital domain.
>
>Setpoints and storage -

The Dallas DS1620 is digital and also has set point outputs for HVAC
control. The digital comm is not async data. On a past design, I used the
DS1620 to sense temp then I controlled the contrast on an LCD for good
reading from -20 to 160F.

>I need a simple RS232 type interface with a PC to send
>OK, the '84 gives me EEPROM, so thats nice.  No built-in UART. Has anyone does
> RS232 comm

Check ECH for bit banged serial comm. You can easily get 9600 from any 4Mhz
part.

craig




________________________________________________________
Dr. Craig Hollabaugh
Wireless Scientific, Inc.
1890 South 14th Street
Building 100, Suite 105
Amelia Island, FL 32034
904 261 6977
904 261 2129 fax
.....wsciKILLspamspam@spam@net-magic.net

Or you might know me as
Dr. Craig Hollabaugh
Analog Microelectronics, Georgia Institute of Technology
hollaspamKILLspammonique.adgrp.gatech.edu

or

Dr. Craig Hollabaugh
Aerospace Department, University of Texas, Austin
.....hollaKILLspamspam.....cfdlab.ae.utexas.edu

1996\06\06@152529 by mike

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In message  <EraseME199606061432.IAA01216spam_OUTspamTakeThisOuTvidiot2.corp.es.com> PICLISTspamspam_OUTMITVMA.MIT.EDU
writes:
> Latest thing to hit me is a temperature controller.  What I'm replacing (this
is
>  real
> disgusting) is an embedded PC, using a STD CPU card, a A/D and digital output
>  card, plus
[snipity snip]

Yes I have done this. I use a Dallas part, 16C84 at 4Mhz and rs232 at
9600 baud.

The Dallas chips work as per the data books, although I haven't tested
the extremes of their temperature range. The 1-wire interface is not
too hard - I got it going in an evening. I posted the code on the list a
couple of weeks ago. The data rate (as I remember) is abit more than
9600, but less than 19200 baud. Conversion takes 1 second max.

The DS1821 is available in a TO-220 package which lends itself nicely
to being bolted to a heatsink.


Regards,


Mike

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