[arm-allstar] Adding sensor

[Willem Schreuder]

On Thu, 28 Feb 2019, "Doug Crompton via ARM-allstar" wrote:

> All you need is the 1wire to USB interface and you can daisy chain the 
> sensors wherever you want.

Using the USB interface is probably more tolerant of high RF.  You can 
also get some HATs that do a bit better isolation or for the very brave 
the kernel supports connecting straight to pin 18 if you enable the kernel 
module in raspi-config.

If you want a more off-the-shelf but very robust solution I have used 
these
   https://www.embeddeddatasystems.com/OW-SERVER-1-Wire-to-Ethernet-Server-Revision-2_p_152.html 
I buy the server from EDS ($100 for a fully self contained and hardened 
ethernet based web server designed for industrial use) but buy the sensors 
from Mouser or a similar source and wire them up myself for a tiny 
fraction of the cost of buying their sensors.  For example, the DS18S20+ 
temperature sensor is about $3 each from Mouser in a TO92 package ($4.50 
from EDS), so I put one on the heat sink of every machine and just wire 
them all in parallel.  Read time is about 1 second per sensor.  EDS also 
sells some "packaged" sensors but that gets expensive fast.

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Dr. Willem A. Schreuder,  President,  Principia Mathematica
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