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  • itanic
    replied
    Thanks again Michael for the reply,

    In thinking about your comments, its seems like it would be much easier to attach the senors using all three legs and then combine/solder the two "outside" wires just before they enter the DS9097U rather then 1. sepearte the legs of the sensor 2. fold the third leg at the base of the head 3. add a tiny bit of heatshring so it would not electrically touch the leg it crossed-over 4. solder it to the Gnd leg and 5. clip off the excess beyond the small solder ball.

    Is there any downside to doing this?

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  • Michael McSharry
    replied
    In areas where I have enough slack in the main line I will strip the jacket and untwist the wires sufficiently so I can put a RJ11 plug onto it. If there is not enough slack I have two options. One is to run a "T" off of a RJ11 plug and hope it works and does not break anything else. Sometimes I'm lazy and do this. Other times I will add a length of cat5 "extension cable". Consideration needs to be given to the 300 ft max design length. It may work at 1000 ft, but you need to be more worried about capacitance at longer lengths. I run multiple interfaces to the PC because I cannot make everything work on just one.

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  • itanic
    replied
    Michael,

    Thanks for the quick reply. I'm still a little confused about your statement about adding a sensor "along the line". Do you remove a section of the jacket on the CAT5, untwist the pair you are using and then attach the RJ11 module to it so their is no break in the line or do you allways cut the CAT5 and use the AAG module when you want to add as sensor? What is the model number of the AAG module you use?

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  • Michael McSharry
    replied
    There is not much to look at with respect to the sensor mounted on a RJ11 plug. About 1/2 or 3/4 of the sensor head protrudes from the RJ11 Plug. I mounted mine with the DQ and Gnd pins of the sensor crimped to pins 1 and 6 of the connector. I accomplished this by sepearting the legs of the sensor a little so there would be slight tenson as they were inserted into the RJ11 plug and the crimp would be on pins 1 & 6 rather than some others. Before inserting it I folded the third leg at the base of the head, added a tiny bit of heatshring so it would not electrically touch the leg it crossed-over, soldered it to the Gnd leg, and then clipped off the excess beyond the small solder ball.

    This means that my sensors are all connected on pins 1 and 6 while the standard for sensor's on the RJ11 are pins 3 & 4. The transformation from 1/6 to 3/4, in my case was done at the end of the wire where it plugs into the DS9097U.

    When I add a sensor along the line I will use a modular RJ11 and use a standard airtight pressure contact to tap into the main line. The modules available from AAG mount two RJ11 plugs onto its circuit board. When I connect these then I cut the main line and connect two RJ11 plugs at the cut. These two plug into the two RJ11 plugs on the AAG modules. I have also had cases where I needed to extend the cable somewere in the middle. The extension was done with RJ11 plug/jack and the sensor mounted in the middle of this extension.

    The routing or topology of the wire run is done to increase the probability of successful communication. The best situation is one wire pair of length up to 300 ft with a sensor connected at the end and as many others added along the way as desired. When a sensor is placed in the middle then it forms a "T" connection. The length of the "T" should be the length of the sensor leg. A longer pigtail will introduce a signal path which reflects back onto the main line and can interfere with the data stream. A long "T" may work and a short one may not. A short "T" may work and a long one may not. It just depends upon the timing of the waveform coming down the main line. The probability of success is increased if the "T" is made as short as possible.

    The wire pair also introduces capacitance that is a function of the length of the wire. If all 8 wires in the CAT5 harness have some connection at either end then the capacitance will be increased by a factor of 4. The capacitance reduces the shape and potentially the magnitude of the signal. In the limit it will totally absorb it.

    There are no guarantees, but if you have the option, then I suggest you try to following the guidelines to increase your change of a reliable communication for your current configuration and still be reliable as you add new sensors in the future.

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  • itanic
    started a topic Basic Questions

    Basic Questions

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