Jump to content


Photo
- - - - -

Help w/ wiring DS2438 to pH Meter


  • Please log in to reply
6 replies to this topic

#1 ufans

ufans

    Newbie

  • Registered
  • Pip
  • 4 posts

Posted 03 January 2016 - 09:47 AM

Can someone help verify this circuit and/or suggest changes?
 
Ph monitor

 



#2 jpmargis

jpmargis

    Dedicated Cocooner

  • Registered
  • PipPipPip
  • 390 posts
  • Location:Southern California
  • Experience:average
  • Software:Harmony
  • Hardware:Elk M1
  • Video:Windows Media Center
  • CCTV:ip
  • Phone:POTS

Posted 03 January 2016 - 10:30 AM

The -12VDC connection looks suspicious.  Update your schematic to show the power supplies.  Also, include the manufacturer and model of pH meter.


Edited by jpmargis, 03 January 2016 - 11:00 AM.


#3 ufans

ufans

    Newbie

  • Registered
  • Pip
  • 4 posts

Posted 03 January 2016 - 12:11 PM

Here's an updated schematic:
https://drive.google...WWM3Uk9lSk14R28
 
 
pH Meter is a Hach Pro Series P3.  
http://www.hach.com/...a?id=7639982991
 
For the pH Meter, I am using the 4-wire connection so I have separate 24VDC power running to it as well.



#4 jpmargis

jpmargis

    Dedicated Cocooner

  • Registered
  • PipPipPip
  • 390 posts
  • Location:Southern California
  • Experience:average
  • Software:Harmony
  • Hardware:Elk M1
  • Video:Windows Media Center
  • CCTV:ip
  • Phone:POTS

Posted 03 January 2016 - 01:17 PM

Well, you keep leaving out important details, but I'll offer the following:

   1) There is no -12 VDC.  It's just the ground for the 12 VDC power supply.  Otherwise, you have a major problem!

   2) I don't see a 24 VDC power supply, so I'm assuming that it connects to terminals TB1-3 and TB1-4 as indicated in Figure 2-13.

   3) There is no GND connection on TB1, so this is probably wrong.

   4) The loop resistor should be connected between TB1-2 and ground.

   5) The loop power supply should be connected to TB1-1.

   6) The DS2438 Vad should be connected to TB1-2.

   7) The DS2438 Vsens+ and Vsens- should be connected to ground.

   8) Your loop current to voltage conversions are backwards.

   9) You need a 4.7K ohm pull up on DQ.


Edited by jpmargis, 03 January 2016 - 01:22 PM.


#5 ufans

ufans

    Newbie

  • Registered
  • Pip
  • 4 posts

Posted 03 January 2016 - 05:33 PM

Thanks for the help.. 

 

Here's the updated schematic with some changes.

https://drive.google...iew?usp=sharing

 

Questions:

 Q1) The 4.7K Ohm pull up resister; does that connect from DQ to OW Return Ground ?

 Q2) Do I need to used Vsens+ and Vsens- ?  would that be better than just using Vad ? 



#6 jpmargis

jpmargis

    Dedicated Cocooner

  • Registered
  • PipPipPip
  • 390 posts
  • Location:Southern California
  • Experience:average
  • Software:Harmony
  • Hardware:Elk M1
  • Video:Windows Media Center
  • CCTV:ip
  • Phone:POTS

Posted 03 January 2016 - 08:36 PM

Q1) The 4.7K Ohm pull up resister; does that connect from DQ to OW Return Ground ?

No, the pull up connects to a voltage which is the same as your 1-Wire microcontroller receiver.  Probably 5 VDC.  If your receiver already has a pull up, then you don't need this one.

 

 Q2) Do I need to used Vsens+ and Vsens- ?  would that be better than just using Vad ? 

No, you need to use Vad.

 

BTW, you took several steps backwards on your schematic.  The loop resistor ended up totally wrong and the power supply grounds and filter capacitors are missing.


Edited by jpmargis, 03 January 2016 - 08:57 PM.


#7 OiJeffrey2

OiJeffrey2

    Newbie

  • New Member
  • Pip
  • 2 posts

Posted 15 February 2017 - 10:01 AM

i used to do one of those pen and paper rpg things but then it got disbanded and stuff xD but im totaly up for something like this and what is L.A.R.P?




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users