Searching \ for '[PIC]: F877 - temperature reading without external' 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/microchip/ios.htm?key=temperature
Search entire site for: 'F877 - temperature reading without external'.

Exact match. Not showing close matches.
PICList Thread
'[PIC]: F877 - temperature reading without external'
2004\10\20@093127 by alan smith

picon face
Some micros, such as the Cypress PSoC, have a psuedo
temperature sensor on the silicon.

So, wonder has anyone tried to do the same thing with
a F877 device.  I don't need absolute temp, more along
the lines of if the unit is really cold, try to
compensate the A/D readings.

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
____________________________________________

2004\10\20@100947 by hael Rigby-Jones

picon face


>-----Original Message-----
>From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu]
>On Behalf Of alan smith
>Sent: 20 October 2004 14:31
>To: Microcontroller discussion list - Public.
>Subject: [PIC]: F877 - temperature reading without external sensor?
>
>
>Some micros, such as the Cypress PSoC, have a psuedo
>temperature sensor on the silicon.
>
>So, wonder has anyone tried to do the same thing with
>a F877 device.  I don't need absolute temp, more along
>the lines of if the unit is really cold, try to
>compensate the A/D readings.

It's possible to use the watchdog timer as a crude temperature sensing
device, although it's probably not the most convienient way of measuring
temperature.  A thermistor and a resistor would make a superior solution if
you happen to have an anlog port free, otherwise you can use a thermistor
and capacitor with a normal digital pin and time the charge/discharge of the
capacitor.

Regards

Mike

=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================
____________________________________________

2004\10\20@102425 by Mike Hord

picon face
VERY recently (last 48 hours or so) I saw a post about using
the WDT to do this.  With an accurate time base (crystal),
the WDT varies (fairly) predictably based on temp.

Try it, and search the archive for the other post of which I am
speaking.

Mike H.

> Some micros, such as the Cypress PSoC, have a psuedo
> temperature sensor on the silicon.
>
> So, wonder has anyone tried to do the same thing with
> a F877 device.  I don't need absolute temp, more along
> the lines of if the unit is really cold, try to
> compensate the A/D readings.
____________________________________________

2004\10\20@104724 by Herbert Graf

flavicon
face
On Wed, 2004-10-20 at 09:31, alan smith wrote:
> Some micros, such as the Cypress PSoC, have a psuedo
> temperature sensor on the silicon.
>
> So, wonder has anyone tried to do the same thing with
> a F877 device.  I don't need absolute temp, more along
> the lines of if the unit is really cold, try to
> compensate the A/D readings.

Check the archives, there was talk about doing this with the WDT, since
it's osc is RC based it has a temp dependence, IIRC all you'd need to do
is time how long the WDT took to expire.

Only problem is it is very likely very device dependant, so one 877
might be very different then another 877, but if you can calibrate it
per device then that shouldn't be a problem. TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

____________________________________________

2004\10\20@105255 by Mcgee, Mark

flavicon
face
Forgive me, but I haven't been following this thread.  I'm working on a
temperature control module at the moment, to control the fermentation
temperature of my homebrew beer.  I'm using a temperature control
module(FE33L) from Maplin, but now I've discovered PIC's I wonder if I need
that any more.  Although, it does have an LCD display.

The temperature module is correct to 1-degree-C IIRC, and outputs a 13-bit
proprietry sequence representing the temperature every 10 seconds via a serial
output.

Is it possible to beat that accuracy for 0C to 25C range myself?  I would also
have need for a 60C to 85C range too.  How would this be implemented using a
PIC?

Regards
Mark

==============================================================================
This message is for the sole use of the intended recipient. If you received
this message in error please delete it and notify us. If this message was
misdirected, CSFB does not waive any confidentiality or privilege. CSFB
retains and monitors electronic communications sent through its network.
Instructions transmitted over this system are not binding on CSFB until they
are confirmed by us. Message transmission is not guaranteed to be secure.
==============================================================================

____________________________________________

2004\10\20@105542 by \.genovesi\

flavicon
face

If you don't want external components, you can use the watchdog timer temperature dependency.
See AN720 - Measuring Temperature Using the Watchdog Timer (WDT)

http://ww1.microchip.com/downloads/en/AppNotes/00720c.pdf


regards
Marco




---------- Initial Header -----------

>From      : piclist-bouncesspamKILLspammit.edu
To          : "Microcontroller discussion list - Public." .....piclistKILLspamspam.....mit.edu
Cc          :
Date      : Wed, 20 Oct 2004 06:31:26 -0700 (PDT)
Subject : [PIC]: F877 - temperature reading without external sensor?

{Quote hidden}

> ______________________________________________

2004\10\20@112551 by Dan Smith

face picon face
On Wed, 20 Oct 2004 09:24:21 -0500, Mike Hord <EraseMEmike.hordspam_OUTspamTakeThisOuTgmail.com> wrote:
> VERY recently (last 48 hours or so) I saw a post about using
> the WDT to do this.  With an accurate time base (crystal),
> the WDT varies (fairly) predictably based on temp.

Jinx's post on this topic is at
http://massmind.org/techref/microchip/jinxwdttemptest.htm

Dan
____________________________________________

2004\10\20@124354 by Mcgee, Mark

flavicon
face
I should probably add, how would I implement this with an external probe and a
PIC?

MM

{Quote hidden}

> ______________________________________________

2004\10\20@144038 by Jan-Erik Soderholm

face picon face
Mcgee, Mark wrote :

> Forgive me, but I haven't been following this thread.  I'm
> working on a temperature control module at the moment,
> to control the fermentation temperature of my homebrew
> beer.  I'm using a temperature control module(FE33L)
> from Maplin, but now I've discovered PIC's I wonder if I
> need that any more.

The FE33 module seems like it was ment to be used
stand-alone. It's hard to set any alarm levels from
the PIC, you are expected to look at the display
while "programming" it, a bit like a normal alarm-clock.

So what's left is the temp measurement, and that could
also be done with some simple SPI/I2C/whatever temp-
sensor.

> Although, it does have an LCD display.

But you can not use the LCD from the PIC, as far
as I can see. You have no control over it.

> The temperature module is correct to 1-degree-C IIRC,...

Within -10 - +40 deg C, yes.

> and
> outputs a 13-bit proprietry sequence representing the
> temperature every 10 seconds via a serial output.

Isn't different from any standard temp sensor. Some
outputs a 12-13 bit binary value, some a BCD code.

> Is it possible to beat that accuracy for 0C to 25C range
> myself?

Depend on your definiton of "myself" :-)
Check what Maxim/Dallas has to offer. Just to name one.
There are a *lot* of different temp sensors out there.
I jst looked and there are 119 different "Temperature Sensors
and Temperature Switches"... As usual with Maxim, 95% of
them are SMD... B.t.w, just checked what Texas have on their
"sampleable" list ad it was 8 temp sensors, or SMD. Now, temp
sensors are usualy 3-6 pin, so SMD might not a major problem.

> I would also have need for a 60C to 85C range too.
> How would this be implemented using a PIC?

It's not PIC dependent, it's up to the temp sensor. But
the range isn't anything un-normal. Most/many sensors work
up to 125 deg C.

Jan-Erik.

____________________________________________

2004\10\20@153502 by Jan-Erik Soderholm

face picon face
Mcgee, Mark wrote :

> I should probably add, how would I implement this with an
> external probe and a PIC?

Depends on the type of external "probe".
Most new/modern temp sensors for "normal" temp ranges
(usualy -40 -- +125 deg C) are electronic devices
and outputs a digital signal. Can use 1-wire (Maxim/Dallas)
or the more common SPI or I2C interfaces. A PIC would
just "see" them and read from them as any other device, EEPROM
or whatever.

Then there are temp sensors that outputs some mV's / degC.
You have to use the ADC and you'll get more issues with noice
on the line from the sensor to the PIC.

For higher temp ranges there are other (passive) solutions.

Jan-Erik.
____________________________________________

2004\10\20@190217 by Jinx

face picon face
> The temperature module is correct to 1-degree-C IIRC, and outputs
> a 13-bit proprietry sequence representing the temperature every 10
> seconds via a serial output

> Is it possible to beat that accuracy for 0C to 25C range myself?

I would be fairly confident using WDT over that range. AFAICT a
PIC's WDT variation to temperature is linear. I've used it at household
ambient as a data-logger and it compares very well to a good mercury
thermometer. One day I should compare it to a temp sensor but that's
hardly 10 Ten Things To Do

Two points to watch out for are Vcc, which must be same as when/if
the PIC was characterised, and the thermal response time. Obviously
the 877 is a pretty hefty chip and takes some time to stabilise. Either add
a heatsink to the 877 or use a smaller PIC, eg 12F or 16F

Downsides -

PIC will have to be immersed (Duke Of Clarence can tell you how that
might go - if he wasn't dead that is ;-)) )

To be sure, you'd need to characterise the PIC. This is time-consuming
and for a one-off is more an academic exercise than a money-saver.
You'll have to write s/w and set up a test rig

> I would also have need for a 60C to 85C range too.  How would
> this be implemented using a PIC?

Commercial grade devices won't be reliable at 85C

____________________________________________

2004\10\21@054533 by Mcgee, Mark

flavicon
face
Yes, the FE33L is a standalone unit - I discovered PIC's and this list for the first time after I decided that I'd optionally want send the output from the FE33L to a PC for logging - but the unit would still need to work without the PC connected, as in fact it would be most of the time.

The LCD display is useful for displaying the current temperature so I can see instantly how my brew is doing, and setting the high/low temp alarms manually (a PIC programmable interface would've been nice though) - the external probe will be attached to a fermentation bin, inside a chest freezer, and the display/control module outside.

At some stages of fermentation, you want to step down the temperature over a couple of days to your final fermentation temperature (and possibly back up again for a diacetyl rest, and then back down again for conditioning! - if anybody's interested, this gives lager a cleaner taste, and takes away any butterscotch flavours).

So hooking up the PC to override the FE33L's alarm signals via the PIC is what I intend to do - as the PIC doesn't have a real-time-clock.  What would be nice is to hook the PC up, program a few steps (temp and duration in hours/days), then disconnect the PC to let the stand-alone unit do it's thing.

The temp range for this kind of operation would be 0C - 25C.  The other range I suggested 60C-85C would be for mashing/decoction monitoring, and would be a separate unit to the fermentation controller.

I like the idea of a standalone temperature sensing module with I2C output.  Do these kinds of units work with an external probe/wire?  I'd appreciate any product recommendations.

Of course, then I'd need to control an LCD display - something I know nothing about....

The FE33L module was about £10 IIRC, it'd take a fair bit of effort to beat that price as a non-trade punter, I think.

Cheers,
Mark


> {Original Message removed}

2004\10\21@062741 by Jan-Erik Soderholm

face picon face
Mcgee, Mark wrote :

> So hooking up the PC to override the FE33L's alarm signals
> via the PIC is what I intend to do

You still have to switch/change temp sensors, since the FE33
only have one sensor input. This could be done from the PIC
application, of course.

> - as the PIC doesn't have a real-time-clock...

It does, if you want  :-)
Either use the main crystal as a timebase, or hook up a special
"clock-crystal" to TMR1. Check the data sheet for examples.

> What would be nice is to hook the PC up,
> program a few steps (temp and duration in hours/days), then
> disconnect the PC to let the stand-alone unit do it's thing.

Sure, no big deal for the PIC. Write the application in a generic
way that reads a "processing-scheme" downloaded from the PC.

> I like the idea of a standalone temperature sensing module
> with I2C output.  Do these kinds of units work with an
> external probe/wire?

Some. Most are in one unit.

>  I'd appreciate any product recommendations.

There are just *so* many of them :-)
And a lot of different features. Some have builtin
programmable alarm levels and so on.

This seems to be one popular unit :
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2815/ln/

I'm not sure how I2C or SPI performes over longer (several
meters) distance. Maybe the 1-Wire is better in those cases,
I'm not sure...

But check http://www.maxim-ic.com for the whole range.

> Of course, then I'd need to control an LCD display -
> something I know nothing about....

Lots of code examples on the net (such as the PIClist archives).
Quite easy actualy if it's a standard Hitachi interface.

> The FE33L module was about £10 IIRC, it'd take a fair bit of
> effort to beat that price as a non-trade punter, I think.

Surplus LCD's could be found cheaper than that.
It depends on the type (size and backlight).

Regards,
Jan-Erik.
____________________________________________

2004\10\21@202135 by Steve Mercer

flavicon
face
Seems like you are doing something kinda close to what I am doing. My project (First one for me with PIC) is a Temperature/Time controlled switch for a 240V bar heater. The user sets the on time and off time on specific days of the week and then sets a temperature. The box then switches a 240V output socket on and off as required.

So, for the real Time Clock I'm using a Dallas DS1307 I2C RTC (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2688) and for the LCD display and switches an LCD module I got from eBay (cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3846151274). The Temperature sensor is the Dallas DS18B20 1-Wire (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2812). This sensor is designed to be mounted externally somewhere in the region you would normally sit.

As a new user of PIC's and a currently employed programmer, I first learned a bit about programming in assembler and then decided a higher level language was better (For me). As I work mainly in C/C++ I thought that would be the best way to go. In reality I found it highly confusing as what I could normally do in my day job with 32/64 bit processors did not switch over nicely to 8 bit microcontrollers. I finally decided to go back to an old favorite from school - BASIC. The compiler I went with is from MikroElektronika (http://www.mikroelektronika.co.yu). It has built-in libraries for everything I need (I2C, Dallas 1-Wire and LCD displays).

I hope some of this helps. If you need more info, do not hesitate to ask.



Steve



{Quote hidden}

___________________________________________

2004\10\22@032009 by Jan-Erik Soderholm

face picon face
Steve Mercer wrote :

> ...and for the LCD display and switches an
> LCD module I got from eBay
> (cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3846151274).


May I ask, what do you think about that one ?
Jan-Erik.
____________________________________________

2004\10\22@062836 by Mcgee, Mark

flavicon
face
Hi Steve

Thanks for the links, I'm sure they'll come in very useful.

I should probably have a look at the BASIC compiler, but this project is
mainly for fun, with some purposeful end result, and going back to my
programming origins and doing assembler is for some reason very appealing to
me!

Cheers,
Mark

> {Original Message removed}

2004\10\24@215722 by Steve Mercer
flavicon
face
>Steve Mercer wrote :
>
>>  ...and for the LCD display and switches an
>>  LCD module I got from eBay
>  > (cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3846151274).
>
>
>May I ask, what do you think about that one ?
>Jan-Erik.

Very nice. Very professionally made and looks really good. It is the
perfect size for my current project.

About the only thing I would have different (And may do anyway) is
change the second red LED to green.
____________________________________________

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...