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  1. #1
    RC poster
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    Apr 2018
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    TRX-4 Telemetry Expander Sensor and speed issues

    Hi all, first post for me in the forums.

    Got myself a TRX-4 and last week I added the telemetry expander last week. I wanted to monitor motor temperatures and speed.
    The expander wasn’t working at the beginning, the app was trying to update the firmware without success so I had to return it back to the supplier, they upgraded it and send it back to me.
    Now the only thing that works is the voltage sensor #6527 which I use with the Power Tap for Voltage Sensor #6541 to monitor my battery.
    My two temperature sensors #6526 are registering at “volt” type in the app and don’t show any temperatures. Also, no RPM or speed.
    I tried different phones, both android and iphones, changed locations of the sensors in the expander without any success.

    Anyone has any advice / similar issues?

  2. #2
    RC Enthusiast
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    Aug 2011
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    CT
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    I think with that expander you also need the GPS module #6551 to get speed, I'm not sure why the temp sensors are registering as voltage ones though.
    Garage: 33 Cars
    Traxxas 16
    Other 17

  3. #3
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    Apr 2018
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    Brighton, UK
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    Thanks ToxicSword, I have seen videos online where people are using their electric cars without the GPS module. I mostly use the TRX-4 in muddy woodlands, I am not sure the GPS will have any good signal under the trees to show my speed (And I don’t want to pay £80 for it too).

  4. #4
    RC Racer
    Join Date
    Jun 2004
    Posts
    173
    To get speed you need a sensor and a magnet mounted to the spur gear. As far as I know there is no sensor mount for the speed signal on the trx4. I get temp and voltage using this.
    https://m.traxxas.com/products/parts/telemetry/6521

    Just plug it into your receiver V/T port and hook up the red connector to your battery positive wire to get your battery voltage. Wrap the temp sensor around your motor. The red connector is actually meant to plug into your receiver to give you a voltage reading on your receiver battery voltage but since the trx-4 is using a BEC that should just be a constant 6 volts out of your speed controller so no need to watch that unless your having issues and wonted to see if that was causing something.

  5. #5
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    Apr 2018
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    Brighton, UK
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    Thanks Toadster25, I am actually surprised that speed and RPM is not available directly through the ESC. I sent back the expander and two temp sensors today, hopefully they can check them and send replacements if both are faulty (!). I am sure that I saw videos online where people got the expander plugged on the electric cars and got speed straight to their phone screen.
    I really don’t wont to pay £80 for the GPS unit…

  6. #6
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    Join Date
    May 2018
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    Any updates on this topic?

    My TRX-4 expander can't update either. it stops at about 5%
    no joy on temp and voltage with separate sensors.
    I am going to order the trx-6521 and hopefully that works for me too...

  7. #7
    RC poster
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    Apr 2018
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    Quote Originally Posted by aad007 View Post
    Any updates on this topic?

    My TRX-4 expander can't update either. it stops at about 5%
    no joy on temp and voltage with separate sensors.
    I am going to order the trx-6521 and hopefully that works for me too...
    Had to send my telemetry expander back to Modelsport UK which they updated and returned in 2 days. That worked but then I resent it back with the two auto temp sensors and still waiting to hear back from them.

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