# Temperature Sensor with a Pulse Output

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#### Denis O'Connor

Is there such a sensor that anyone is familiar with in the 0 to 100 degree F range?

I am envisioning a unit that would be programmable to put out 42 pulses every 15 minutes when the temperature is 42 degrees F.

Denis

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#### Willy Smith

Denis,

You could make such a device with two packages: a Dallas IIC temperature
sensor and a Microship PIC or Atmel TinyAVR microprocessor. That makes two
8 pin SOIC devices. A c-compiler is available for the TinyAVR for about
$200 from Imagecraft Software (www.imagecraft.com). Regards, Willy Smith Numatico, SA Costa Rica E #### Eric Nelson Hi Denis, Can I ask WHY you need the pulse output? I doubt that such a sensor exists (though I could be wrong!). Maybe some more application info would help us list members find a different way to go about it. What are the pulses being used by? If you can't find this type of sensor, I have a possible solution. Just connect an appropriate temperature sensor to an analog input of a PLC, and write a simple program to give the desired output. I know it sounds like overkill, but AutomationDirect just released an analog input module for their DL05 PLC. At just$99 for the PLC, and \$69 for the module, you have
your "special" temperature sensor, PLUS a handful of digital I/O to use for
other control.

Good luck in any case!,

- Eric Nelson
Controls/Software
Packaging Associates Automation Inc. [email protected]
Rockaway, NJ, USA

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#### Gerald Beaudoin

Temperature sensor with pulse output:
I have not seen any such animal in a neat and tidy package aleady put together,
BUT, some years ago I did work on a degree-day counter which had a pulse output.
These devices work by heating a temperature sensitive device (usually a
resistor) which is inserted into a bridge circuit. When the bridge becomes
unbalanced, a comparatror circuit outputs a pulse and turns off the heat source
until the sensor has cooled off. If the probe, consisting of the heat source and
the sensor, are places in a cool place, the number of cycles will increase,
while the number of cycle will decrease if the probe is in a warmer surrounding.
This principal can be easily calibrated for any temperature range and the common
application was to measure heat units for heating oil delivery companies. This
is how they always know just when to show up at your door just before the tank
goes dry......even if you have just gone through a spell of -30C weather!
Hope the idea helps....

Gerald Beaudoin

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#### Mitch Carr

Eric,

Actually it makes perfect sense although we never did one because we didn't
want to cut our own throat.

Virtually no small PLC has an analog input much less a T/C input but ALL
small PLCs take a pulse input.
A T/C with a pulse output gives you tremendous capabilty at very low price.

Cheers,
Mitch

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#### Tanweer Ahmed

Hi Denis,

You can get it with a simple pt-100 too. Calex makes such signal
whatever system you are using, can input this pulse signals. As far as
number of pulses and the temperature range is concerned in a PLC this is
very simple. If you need further explanation you can directly write me at [email protected]

Regards,

Tanweer Ahmed

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#### R A Peterson

But several companies make analog to pulse convertors for just such use.

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#### Eric Nelson

Hi Mitch,

You definitely gave me a great example to answer my "why" question! This
would be an ideal way to measure temperature with a "very" low-end PLC.
Seems that these pulse output sensors do exist, yet I've heard nothing about
what they cost. If they're inexpensive, then it's an ideal solution. I'd
still like to know the end use (of this pulse output) that Denis actually
needed it for. Is it actually connected to a digital input of a PLC, or did
he have something else in mind? From the range, I'm assuming he's just
monitoring ambient temperature (in a control cabinet maybe?).

- Eric
[email protected]
Controls/Software
Packaging Associates Automation Inc. [email protected]
Rockaway, NJ, USA

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#### Johan Bengtsson

Actually at least one exist. Mitsubishi manufactures a small PLC with
a really (for PLC:s) low price.
I think there is something like 6 or 8 inputs, individually selectable
between digital and analog.

If this is too expensive you probably have to build something on your own
as someone else suggested, based on for instance a PIC16C710 from Microchip
or something similar.

Johan Bengtsson

Box 252, S-281 23 H{ssleholm SWEDEN

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#### Denis O'Connor

I am currently testing a device that reads pulses from up to 3 utility
meters and posts the information to the web twice per day via a phone line.
If I could convert a temperature signal to a pulse input, I could use the
device as a BTU meter for measuring chilled water plant output also.

The main advantage of this pulse counter that is being beta tested is the
posting of data to the internet.

Thanks for everyone's input!

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#### Steven Landau

Take a look at devices from SensorPulse. They ar signal conditioners which =
convert Analog to Pulse exactly for using analogs in small PLC's.

S. Landau
SPEC
The Engineers Who Build.

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#### Hamid Danesh Pazhooh

Dear Denis,

Check the Smartec smt-160-30 which is a nice pulse output temperature sensor. Full story at:www.smartec.nl

Regards,
H. Danesh

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#### Harry Trietley

Your question was just forwarded to me. I don't know if you ever found the answer you wanted. It looks like you got some good ideas suggested.

(I hope this reply is not too commercial - but here goes.)

If you have not found an answer, or if you don't want to do your own designs, my company manufactures signal conditioners and is strong in specials and custom designs. If you're looking for someone to design and build it for you, please let me know.

Our answer would not be a stand-alone sensor, but rather an electronics interface between a standard sensor and whatever your receiver is.