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  • Author Author: verrverr
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Pas Home / Eagle 7.1.0 Pro First design

verrverr

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In my project I plan to modify an existing circuit because it has too many communication errors with the sensors. In a future blog I will try to see the problem with the oscilloscope. Do you see errors to correct? Will the new scheme all the resistors are essential?

 

Dans mon projet je planifie de modifier un circuit existant car il a trop d'erreur de communication avec les capteurs. Dans un blog futur je vais essayer de voir le probleme avec l'oscilloscope. Est-ce que vous voyer des erreurs a corriger ? Est-ce que dans le nouveau schema toute les résistances sont essentiel ?

 

The captor are 1-wire temerature sensor DS18B20+

 

My current schematic

 

image

 

My proposed new schematic

 

Use DS2482S-800+ to isolate each sensor communication

image

Reference schematic

 

imageimage

I follow this lesson https://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/ds18b20

Attachments:
EagleFile.zip
  • in reply to kipe

    The issues experienced with a old Pi model B i will try b+

  • in reply to michaelwylie

    Sorry it was the regulator, but I forgot he was already using a RPi   ...as pointed out.

     

    Obviously it can't run on 5v ...so yes it needs to run 3v3.

     

     

    Mark

  • Judging by the schematics posted above, 3.3V is coming from the Pi. The 3.3V line is rated (if I remember correctly) at 500 mA, which should be enough for this kind of use. I don't however have any idea if the Pi uses this line also.

     

    For my design I'm planning on using a separate regulator for controlling the devices I need from a separate regulator, so I can debug the system isolated from the Pi. I've done some initial test with the current design, but these aren't in any way complete. Not actually sure if the design will be ready for the deadline of this design challenge, although I'm aiming for it. If reminds me in a few days, I can test my current Onewire network with a similar setup just to see if I experience similar problems.

     

    Just out of interest, were the issues experienced with the Pi B+? This is because the old Pi had quite picky power circuit, which has caused me a lot of problems before...

  • in reply to mcb1

    That's a good idea. The voltage drop across that much wire could be significant.

  • I wondering if the issue is with the on board 3v3 regulator.

    Generally speaking they are much lower current rated than the 5v ones.

     

    Have you tried sticking a 4700uF or larger across the 3v3 line.?

    Now that you have your scope you could check to see it is 3v3 and that there is no noise on it.

     

    Is it possible to run your micro on 5v.?

     

    re level translators

    The general rule with any IC is never apply a voltage to any pin greater than the supply voltage. (unless it's special purpose pin)

     

    Mark