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FAQ
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FAQ
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DigiTemp Frequently Asked Questions
Copyright 1996-2018 by Brian C. Lane <bcl@brianlane.com>
http://www.brianlane.com
http://www.digitemp.com
Q. Where Do I buy Parts?
From www.ibuttonlink.com
I have discontinued my hardware products so that I can spend more time on
software. ibuttonLink makes a great serial adapter, and they have picked
up production of my DT1A sensors.
www.aagelectronica.com produces a full line of 1-wire products at a
very reasonable proce, including temperature sensors, humidity and pressure,
weather stations, hubs, etc.
Places to avoid are www.buffalorun.com, all I see are numerous complaints
on the mailing lists about how he doesn't deliver and doesn't communicate.
If you want to build them yourself you can get parts from either
www.maximic.com or www.digikey.com for sensors. For serial port adapters
I now recommend using iButtonLink instead of DS9097U's -- Maxim raised
the proce so much that the little extra you spend for the Link is well
worth it.
I order my temperature sensors directly from Dallas Semiconductor
at 1-800-336-6933 (http://www.dalsemi.com/sales/credit_card.html)
DigiKey (http://www.digikey.com) now has DS18S20 sensors in stock as
well.
Q. How do I connect it to the RJ-11 of the DS9097U
Take a look at the DS9097U data sheet at
http://pdfserv.maxim-ic.com/arpdf/DS9097U-009-DS9097U-S09.pdf
Ground is the pin on the right and data is the pin on the left (using
the two center pins of the RJ-11).
Even with this information you will probably get it backwards the first
time so make a temporary connection the first time and confirm that
you have the correct polarity.
Holding the RJ-11 plug so that it is facing you (as if you were going to
plug it into your mouth), with the clip on the top.
____
--| |--
| 4321 |
--------
1 = NC
2 = Ground
3 = Data
4 = NC
The same applies for the RJ-45 connectors.
Q. How many can I connect?
Read the Dallas Semiconductor Tech. Brief on the One Wire Network.
http://www.maxim-ic.com/appnotes.cfm/appnote_number/570
It covers everything you want to know and more. The limit comes down to
wiring, how much you have and how good it is. Other than that you can
connect as many as you need.
www.pointsix.com also has some very good app notes on network length
and ringing problems.
Having a 1-wire hub for complicated netowrks and supplying +5v instead
of using the sensors in parasite mode will also help you create larger
and more reliable networks.
Q. How long can the wire be?
Again, read the Tech. Brief above. This depends on the cable. Using
better cable will allow you to extend the cable longer distances. CAT5
is the recommended cable for networks of almost any length. You can get
away with other cable but be prepared to rip it all up and replace it
with CAT5 if it doesn't work.
Having a hub and supplying +5v to the sensors will increase the liklihood
of your long network operating properly. I have had reports of people using
CAT5 and a passive network up to 200m long.
Q. I get a result of 85C when reading temperatures
85C is the error state of the DS18S20 sensor, and it usually indicates that
one of 2 things are wrong:
1. If you are using parasite powered sensors you forgot to ground the +5v
pin to put the sensor into parasite mode.
2. You are trying to read the sensor too quickly. The DS18S20 needs about
750mS of delay in order to properly convert the temperature.
Q. I have glitches in my data, what do I do?
The first solution is to check all of your connections to make sure
they are soldered or well connected.
Next, is your cable decent quality? Cat-5 is the best, with twisted
telephone cable coming in second.
If you are still having problems you should try Using a Schottky
diode across the cable's end. Connect the diode reverse-biased with
the cathode (the stripe) on the data line and anode on the return.
I used a 1N5818 across my attic sensor -- before adding this I was
getting multiple glitches per hour. Now I have seen 1 glitch in
about 2 weeks.
You can also buy pre-assembled sensors that include a 1N5817 diode from
my DigiTemp Hardware page at http://www.brianlane.com/dthardware.php
Q. What is the difference between the DS9097-U and the App. Note 74 type
of adapter.
The DS9097-U adapter uses a serial port to 1-wire conversion chip that
makes talking to the 1-wire network easier. DigiTemp v2.x uses this
type of adapter (the DS9097U-009 and -S09 both work fine).
The old style of adapter (sometimes called passive or App. Note #74)
used only diodes and resistors to convert the serial port voltages to
the one-wire voltages. Dallas still sells adapters of this type, part
number DS9097 and DS9097E that is built on this design. DigiTemp v1.x
supports this type of adapter, and include a HOWTO document with
instructions for building your own.
As of DigiTemp v3.0.0 support for both style adapters has been integrated
into the same code tree. You no longer need to use v1.x for the DS9097 passive
adapter and v2.x for the DS9097U adapter.
Q. When will digitemp support the one-wire hub?
It does! As of v2.3 it scand for the DS2409 couplers used in the hubs
and keeps track of which branch it finds the sensors on. It doesn't
support cascaded hubs (hubs connected behind a hub), only multiple hubs
on the main 1-wire lan.
Q. When will Digitemp support the one-wire Weather Station?
Probably never. DigiTemp has 1 purpose - to read temperatures. Weather
station support is more complicated and requires a dedicated program to
be watching the station and recording events like weather vane movement
and wind-speed calculations. I may add support for humidity and
barometric pressure, especially if someone were to donate a unit for me
to use.
I have found a possible source for Humidity, Barometer and Lightning
sensors at http://www.jjware.com/index2.htm
I do have plans to write my own weather station software though. No release
date as of yet, but it is being worked on.
Q. When will it support 1-wire device X?
The quick answer is "When someone sends me one". DigiTemp v3.3.0 now has
support for the DS2438 battery monitor which is used in many of the more
complicated sensors, like humidity and pressure. It also has native
support for humidity using the AAD TI-8540 humidity sensor.
Q. Will the DS2490 USB to 1-wire adapter work?
Maybe. I have reports of varying levels of success with it. On my Debian
Sarge system using libusb 1.4 it does not work. On my Fedora Core 3
laptop it worked sometimes. On OSX it does not work. Some people report that
it works fine for them, others are like me and have mixed results.
Version 3.7.0 may improve this, a usb buffer was not being cleared before
being used. Running the new code on my Fedora 23 system overnight worked
without any errors.