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Author Topic: Noob with 18S20 Weirdness  (Read 994 times)
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Hello and thanks for your patience. I an new to Arduino, but I did digital design and micro controller apps for over a decade ending about 15 years ago. I know c cold, but c++ is a 'work in process' at the moment.

I am trying to build a home monitoring system. I successfully downloaded and ran applications for a DHT22, and now I'm trying ot do the same for an 18S20. I have pretty much used the various application examples such as the Arduino Onewire library and the library for Dallas Temperature ICs. In the Dallas Library it says "DS18S20 - Please note there appears to be an issue with this series." but it doesn't say what that issue may be or how it presents itself.

Besides redefining the I/O pin, I added a couple lines of code to trace. This is what I get from the code

Dallas Temperature IC Control Library Demo
Locating devices...Found 1 devices.
Parasite power is: ON
Device 0 Address: 10CFDFDB01080039    Device 0 Addr[0] 10
Device 0 Resolution: 9
Requesting temperatures...DONE
Temp C: 85.00 Temp F: 185.00


The first bit of weirdness if that I have wired the device not to use Parasite Power, but it is reporting that it is using parasite power. Whether I wire it as parasitic or not and whether I 'force' the code to not use the parasite power, the reported temperature is always 85.00/185.00 (its about 25/80) in my room.

The fact the device reports an address is encouraging as it shows its not dead.

Are there any suggestions? Does anybody know what the 18S20 'issues' are?

Thanks
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Just in case anybody else comes looking, I found in another Arduino forum that the 81S20 wants a delay (used 750 mSec) between issuing the read temp command and reading it back.

I don't know why it thinks its in parasitic mode (I'm working on it) but I can now read the correct temperature.

 smiley
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I don't see I can edit the prior post, but the root problem comes from the fact the example sketch calls

 sensors.requestTemperatures(); // Send the command to get temperatures

instead of

 sensors.requestTemperaturesByAddress(insideThermometer); // Send the command to get temperatures

the 'by address' call looks at the LSB of the device address, recognizes the device as an 18S20 and inserts a 750mS delay. The sensors.requestTemperatures(); call does not do such a check as it looks at the device resolution (9 bits) and uses a 94 mSec delay

Still working on the power state misread - though it does not seem to affect the operation of the device.

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Hi Mingi, last week I got to work 2 of these sensors in a single pin. I used the one wire library. I founded a post where they first searched for the unique code of each one and then with another code I could read each sensor independently.
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nayma

That's great! I only picked up one at the store, but I did get a similar Temperature/Humidity sensor. I figured once I got it to work I'd go buy some more, but then I broke my leg and I'm stuck in wheel chair for a few weeks at least smiley-sad

What type of project are you working on?

A few years ago I built a house with hydronic heating (hot water in the floor) and I want to accomplish a few things with my project:
1) Remotely monitor/alarm room temperatures and the function of the geothermal system
2) Better control the 'zoning' so I don't waste energy over heating rooms.

I figure an Arduino with an Ethernet shield, some temperature sensors, and an I/O board (opto triacs and opto isolators) should do it.


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