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Topic: dallas temp sensor review and help / (one wire) (Read 1 time) previous topic - next topic

daidalos

Sep 11, 2007, 01:03 am Last Edit: Sep 11, 2007, 01:06 am by daidalos Reason: 1
ok guys ... I need a hand or two

I've read this entire thread and learned quite a bit about these temp sensors (one wire)
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1161557194

however ....

I'd just like to double check on my circuit - if anyone had an image for exactly how to wire these up to the Arduino that would be helpful.

I'm running a DS18B20 (is there a major difference between the B20 and the S20?) with the sample code provided in the Playground and using the necessary OneWire library in 009 programming a new Decimilia.
http://www.arduino.cc/playground/Learning/OneWire


heres my results.....



R=28 F8 9D 46 1 0 0 D4 Device is not a DS18S20 family device.
No more addresses.



So, my first question is .... what are the possible things that could be wrong so that I can start narrowing it down in order to figure out how to use these sensors.

Also, whats your experience been like with these sensors in general (those of you who may have used them) in terms of accuracy?

any help on these things is greatly appreciated.

cheers

daidalos


bigengineer

This is a quote from jims: (2nd page of 1-wire topic)
Quote
I have the grounds connected, the DQ pin on the DS18S20P connected to the pin of the Arduino, and a 4.7kohm resistor from DQ to +5v as the pullup. It is good to connect the Vdd pin of the DS18S20P to ground also so if you get a non-parasite version (DS18S20) it will also work in parasite mode.


Try to use the sensor in parasite mode. Isn't the difference between B20 and S20 described somewhere in the datasheets?

daidalos

#3
Sep 17, 2007, 01:22 am Last Edit: Sep 17, 2007, 01:41 am by daidalos Reason: 1
Hey man thanks for the reply - I'm sorry I missed that -

I went with your circuit and code .... heres what I'm getting through the serial



28 F8 9D 46 1 0 0 D4 read rom

49 1 4B 46 7F FF 7 10 F6 read scratchpad  T =  36 version: 1



and if i put my hand on the sensor it reads



28 F8 9D 46 1 0 0 D4 read rom

80 1 4B 46 7F FF 10 10 C6 read scratchpad  T =  64 version: 1




the difference being the 36 and the 64

just wondering what exactly all this information is - and how to decipher it (I'm assuming of course that T = is the temp reading)

thanks again!


mattt

I've used a a few 1wire devices before.
Check the spec sheets some of the temp sensors have better resolution.

I use a dallas 1wire serial adaptor + linux + owfs, not ardino.

mattt


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