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  • Author Author: verrverr
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Pas Home / 1-wire vs Tektronix oscilloscope

verrverr

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Hello, this week I did a lot of testing and debugging with the oscilloscope. I try to see and solve the problem of my network of temperature 1-wire sensor.

 

 

I try first to change my connection to the 5v and 3.3v use, I also change the cable connection together. Using the 5v is really not advise for raspberry pi but its still work reasonably well for 6 months.

Result : failure no captor are detected

 

imageimageimageimage

 

Then I tried to change the way power sensors using the parasitic mode. As some suggest me in another post

Result : no difference, no captor detected

 

Here are some screenshots of what I normally should have as working signal

With 1 sensor on 3.3v

imageimage

With 1 sensor on 5v and level switcher

imageimageimageimage

According to this guide Guidelines for Reliable Long Line 1-Wire Networks - Tutorial - Maxim my curve have slow rise time and maybe some reflected problem


Finally I retest on 5v but with a level converter https://www.adafruit.com/products/757 to send only 3v on raspberrypi port

Result : Success all captor are detected and all communicated data are correct

imageimageimageimage

Interesting curve. Yellow is the 5v side data and Blue the converted 3.3v result

image

 

I'll do other tests removing resistors supposed to improve communications and see if it really helps and I will also make a soldering version on a perma-proto board.

Do you see anything else that could improve my circuit?

 

Old schematic

image

 

New improve schematic

image

Parents

  • Hi,

     

    Managed to measure from my network built with DS9490R, uses 5 DS18B20's (all in parasite mode), couple of AD-converters etc. Cabling is done with random cables found on my desk, ranging from 0.25 mm² to 1.5 mm². The whole network includes about 30 meters of cable.

    image

    image

     

    As you can see from the captures, the active pull-ups work miracles. I'll try and measure the same network with the DS2482 I suggested earlier, although I'm sure the results should be quite similar...

     

    Also, I forgot to mention before, applies only to parasite power: I had problems before, when I was trying to read the data too frequently. The pull-up didn't have time to charge the internal capacitors of the sensors and this caused the measurements to fail.

Comment

  • Hi,

     

    Managed to measure from my network built with DS9490R, uses 5 DS18B20's (all in parasite mode), couple of AD-converters etc. Cabling is done with random cables found on my desk, ranging from 0.25 mm² to 1.5 mm². The whole network includes about 30 meters of cable.

    image

    image

     

    As you can see from the captures, the active pull-ups work miracles. I'll try and measure the same network with the DS2482 I suggested earlier, although I'm sure the results should be quite similar...

     

    Also, I forgot to mention before, applies only to parasite power: I had problems before, when I was trying to read the data too frequently. The pull-up didn't have time to charge the internal capacitors of the sensors and this caused the measurements to fail.

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