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xapmcs1Wire - 1 Wire (DS9097U / DS9490D) xAP Node

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    #31
    To support your meter then the instaneous current should be reported. The temperature is not needed, nor the discrete.

    When do project to have the the unit available again?

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      #32
      Michael,

      Yes the instaneous current is what should be reported, but also reporting the temperature could be handy. It is always good to have additional temp sensors.

      I should have the moisture meter back in stock tomorrow. I got a parts shipment that I have to go pick up at FedEx this afternoon and it should be the DS2760s I've been waiting for.

      Eric
      www.hobby-boards.com

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        #33
        Eric - onewireviewer reports all zero data. So do I need to resolder the chip (DS2760) or is it some of other support circuits I need to check ??

        Thanks,
        Bruce

        "The universal answer is 42."

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          #34
          Bruce,

          Do you have a leaf wetness or gypsum soil sensor attached?

          I would look at the DS2760 with a magnifying glass and see if solder has bridged between two of the pins. If not then I wouldn't try resoldering that chip unless all else fails.

          Other things you can check is to make sure that power is supplied to the unit, that all the connecions are made correctly, and if you have a multi-meter you can measure the voltage across R2 and see if you are getting anything. It will be a very small voltage.

          If that doesn't work we should probably take further support off this thread. You can contact me at support@hobby-boards.com

          Eric
          www.hobby-boards.com

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            #35
            Eric, What is the relationship between current and moisture with your system of gypsum probe and DS2760? Is it linear or second order? I assume it is represented as a pressure type measure (Kpa) or is there some from of percentage representation?

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              #36
              I've implemented the software to read the device using the same techniques I used for the DS2438 and not having too much luck getting reasonable data. The voltage and current always read 0 and the temperature is always 32. I have the gypsum connected, but it has not been exposed to any moisture. My 12VDC source is filtered and regulated so the power is clean. Is there some test software you use to evalute the operation of the interface? For the Temperature and Voltage readings I do a conversion before reading the result. In the case of the current I just read the value. I have not tried to use any of the other registers, but in general the 1-wire interface appears to be working well. It is just that the voltage/current/temp data values returned are not as expected.

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                #37
                Michael,

                I don't know the exact relationship between moisture and current but I suspect that it is not linear. The gypsum sensor changes resistance based on the amount of moisture present in the sensor. The amount of moisture in a sensor that has good contact with the surrounding soil will vary linearly with the change in moisture in the soil. The thing I don't have any good data on at this point is the change in resistance of the sensor based on the moisture level, I don't think this is a linear situation. I will be doing some experiments to gather some data in a month or two when I can get some time.

                As for the strange readings I have seen situations where the DS2760 seems to get "stuck". You can try removing the power and reapplying it to see if it gets "unstuck". I just had one that I was testing do the same thing.

                I tested your unit before I shipped it and it was registering fine, so let me know if resetting the power doesn't solve your problem.

                Eric
                www.hobby-boards.com

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                  #38
                  Power cycle has no effect. I am able to read the address, but that looks to be about it. I'm running with OWAPI and using the Current, Voltage, and Temperature methods to start conversion and read the result. I have not tried direct communication with the DS2760 registers.

                  I can connect a DS1820 to the DS9097U and the temperature conversion and reading is fine. Only one device is connected to the DS9097U and the DQ/Gnd line between it and the DS2760 is only a few feet long. Power Gnd and device ground are connected together at the board's screw terminal. The gypsum wire is stripped at the end and connected directly to the screw terminals. I measured the 12VDC at the screw terminal.

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                    #39
                    Michael,

                    Try reading the DS2760 while there is no power supplied. You setup sounds almost like my test setup.

                    Eric

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                      #40
                      The 12V makes no difference. Still 32 for Temp and 0 for voltage and current. What software are you using to test the unit?

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                        #41
                        I'm using the OneWireViewer app that comes with the 1-Wire drivers.

                        I'm wondering if there is some initialization that needs to be done to the DS2760 before it will read properly, I seem to remember something about a "sleep" mode. I will look over the spec sheet and see what I can find.

                        Eric

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                          #42
                          I took a look at the DS2760 registers and they all looked reasonable to me. The mode reports as normal and not sleep.

                          A/D range reported at 5
                          Status Reg C7
                          Prot Reg 4F
                          Special Reg BF

                          I also took the scope out and measured a 555 waveform of 4 ms duration and DS2760 sense input at 4.4 mv.

                          I'm guessing that the problem is at the software end. Attached is the software I'm using. It will run with a tray icon. The setup needs to set a com port and polling interval. The raw data is viewable from the tray icon IO window option. If you do not mind can you give it a try with a unit that is reporting properly in your setup.
                          Last edited by Michael McSharry; July 25, 2005, 05:03 PM.

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                            #43
                            Michael,

                            Sure, I'll run your software on a known good unit and let you know the results. It may take me a couple of days to get the time.

                            Eric

                            P.S. Have you tried the OneWireViewer app on your unit?

                            Comment


                              #44
                              I get similiar result with the One Wire Viewer. Note the temp is 32F so the device reading is actually 0. The two AD channels both report 0.

                              Comment


                                #45
                                Michael,

                                I finally got a chance to take a look at the issue you are having. I figured out what it is and I think they changed the default in the chip because I never had to set this register before to get it working. What is happening is that the DS2760 starts in sleep mode and there are a couple of ways to get it out of sleep mode. You can bring pin 10 low (that is what I'm going to do in the next revision of the board). Or you can tell the chip to come out of sleep mode when DQ goes high by writing 20H into memory location 31H. Once you write that value you need to remove the power and connection to the 1-Wire master for 2 seconds, after that it should work fine.

                                Until I get a new batch of boards made to fix this in hardware I will make sure that I set the register in all the units I assemble.

                                Let me know if that fixes your problem and sorry for the troubles.

                                Eric

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