[VicPiMakers Projects] Projects Digest, Vol 6, Issue 5

[James Briante]

Hey George,


Deid has suggested using DS18B20 devices for temperature sensing. It’s
something you may consider using especially in applications requiring
several temperature sensors located at close proximity.  For example, using
two one in and out out of a freezer. These devices are easy to use because
of available libraries for the more common microcontrollers such as the
Arduino & Raspberry Pi.


The DS18B20 and other 1-wire devices can also be interfaced to PCs using a
USB to RS232 and a 1-wire MICROLAN Windows driver.


They are available as discrete devices (3-PIN TO-92 package) or pre-wired
in waterproof leads – all inexpensive and great specs. They are available
quickly from amazon.ca.


The DS18B20 uses the Dallas 1-wire communication protocol which means that
many devices can be connected on a string with just two wires. If there is
only one device on the bus one instruction is issued to read temperature -
Read Rom[33h] . For multiple devices a Match Rom[55h] instruction followed
by the 64-bit Rom address of the device whose temperature value is
requested. See application in the link below.


Interfacing the DS18X20/DS1822 1-Wire® Temperature Sensor in a
Microcontroller Environment (maximintegrated.com)
<https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/162.html>

On Thu, Dec 17, 2020 at 2:55 PM Deid Reimer <deid at drsol.com> wrote:

> Hey George you need to start using DS18B20s to measure temperature.
>
> Deid
> VA7REI
> On Dec 17, 2020, at 12:00 PM, projects-request at vicpimakers.ca wrote:
>>
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>> Today's Topics:
>>
>>    1. Code for turkey stuffed with microprocessor. (George Bowden)
>>
>>
>> ------------------------------
>>
>>
>> Message: 1
>> Date: Wed, 16 Dec 2020 19:10:59 -0800
>> From: George Bowden <gtbowdeng at gmail.com>
>> To: "Talk about Raspberry Pi / embeded projects"
>>  <projects at vicpimakers.ca>
>> Subject: [VicPiMakers Projects] Code for turkey stuffed with
>>  microprocessor.
>> Message-ID:
>>  <CAMon6WtuHHDwC_x=dcDe9vB6YmxR-j+dQ8P0zfcRiZxR+_gYiQ at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Per Lynne's request to see the code, here it is
>>
>> Every few minutes, the microprocessor measures the temperature inside the
>> turkey bag, posts the temperature to a website, and goes into deep sleep on
>> top of the turkey.  (I was going to stuff the micro inside, but that is all
>> frozen up tight)..
>>
>> Because the micro is only awake for a few seconds every 20 minutes, it will
>> run for weeks off the battery, long after the turkey has thawed.
>>
>> The website receiving the post just appends the current local time() and
>> data from the micro processor (humidity, temperature, ADC value) to a log
>> file. The website replies to the micro with the number of minutes that the
>> micro should sleep.  No jason, no mqtt, just php and html.  Webpage file is
>> attached.. "fromdht.php"
>>
>> Here is a snippet of the temperature log
>>
>> 1608169225 90.50 2.50 2704
>> 1608170427 90.70 2.50 2704
>> 1608171628 90.80 2.50 2703
>> 1608172830 91.00 2.50 2644
>>
>> The ADC reading is broken... I thought I could use a GPIO as the
>> source voltage for the thermistor, so that I could turn it off when
>> not needed, but it doesn't work yet.   Maybe need the gpio pin to turn
>> on a mosfet to 3.3volts
>>
>> The Arduino .ino code file is also attached
>>
>> --
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