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Thread: Aux Temp Sensor(s)

  1. #1

    Aux Temp Sensor(s)

    Hello, World...


    ************************************************** ****************
    Am hoping to install one or two auxiliary temp sensors firewall forward as engine fire sensors. Couple questions:
    1. Can the Carb temp be used on an IO engine for this purpose?
    2. Goal is to alarm on sensor overtemp. Can this be user reconfigured in GUI to NOT be carb temp?
    3. CHT/EGT harness drawing 53847WD R2 has pins 1-5 & 14-17 unused. Can these be used for aux temp inputs and alarmed similarly?
    4. Where can I find a drawing of this connector's pinout on the back of the 4500 - its not in the manual as far as I can tell.

    Thanks!
    _________________
    Noah
    RV-7A Finishing
    Saunderstown, RI

  2. #2
    (Copied from old forum)
    rshannon
    Joined: 01 Oct 2007
    Posts: 85
    Location: Sequim WA USA

    If I understand your questions correctly....

    Quote:
    Am planning one or two auxiliary temp sensors firewall forward as fire sensors. Searched the archives and this is the closest thread.

    1. Can the Carb temp be used on an IO engine for this purpose?

    Possibly, but I doubt if the supplied carb heat sensor would work at the high temps you'd want. What temperature do you want to signify "fire"? Then the question is whether the supplied carb temp sensor works to those limits. I don't know, but would think you'd be much better off using a true fire sensor (switch) designed to handle the high temps you want to trigger a fire alert.

    Quote:
    2. Goal is to alarm on sensor overtemp. Can this be user reconfigured in GUI to NOT be carb temp?

    I don't believe so, but the aux inputs are fully and easily configurable. IMHO, unless you already have plans to use all the available aux inputs, you would be much better off using a proper fire temp sensor to trigger one of those -- which can be named whatever you want. When the sensor trips, it pulls the input low (connects it to ground) causing an alarm, etc. The circuitry, logic and configuration of those are easy. (Theoretically, you could even use two or more sensors wired in parallel on just one of the aux inputs. The first to get hot enough closes the circuit, pulling the aux input to ground, and the alert triggers.)

    Quote:
    3. CHT/EGT harness drawing 53847WD R2 has pins 1-5 & 14-17 unused. Can these be used for aux temp inputs and alarmed similarly?

    No, unless you want to break open the 4500 and do a lot of custom wiring and programming yourself. Smile There are no wires (much less programmable functionality) on the EFIS's chassis-side half of the connector for those pins either. They are unused on both sides of the connector.

    Quote:
    4. Where can I find a drawing of this connector's pinout on the back of the 4500 - its not in the manual as far as I can tell.

    As implied by the previous answer, the pinout assignments on the chassis side of that connector are just the mirror image of the cable side. There are no additional wire connections inside the chassis that are not already represented on the cable side diagram of the connector. So there's no need for a separate chassis-side diagram. It would just be redundant.

    Your best bet is to use one of the easily configurable aux inputs, switched by a proper fire temp sensor designed to switch at the high temp of (some kind of) actual fire.
    _________________
    Ron
    Murphy Rebel / Jabiru 3300
    Dual AF-3400EE/EF+AOA
    http://n254mr.com

  3. #3
    Thanks for the response, Ron! Are you a developer for AFS? Just curious since you seem to have some knowledge of the inner workings of the AFS hardware.

    I would not use a carb thermistor/thermocouple, but rather one suited to the temps required (perhaps an EGT sensor or one with equivalent temp capability). I would observe the max lower cowl temp during primary flight test and take the maximum noted temp and add say 100F for an alarm temp. Would need to see how the max temp changes with season and engine power, etc.

    In my case I have an AOA flap switch and aux fuel tip tanks, and am planning to use the aux fuel pump switches (DPDT) as AFS inputs as described in the manual to alarm if you leave the fuel pumps on. Glastar Sportsman installations use this. Anyway, I think this ties up all available switch inputs. Regardless, I would rather have a temp value than a switched input due to the fact that trends would be more indicative of a real problem, whereas a switch fail-on could mean taking improper evasive or corrective action.

    What about the unused inputs for EGT/CHT for a 6 cylinder engine (I have a 4 cylinder)? Are these not internally connected on a 4500 sold to a user with a 4 cylinder engine? Does this also mean that you could never sell your 4-cylinder 4500 to a guy with a 6 cylinder plane somewhere down the road? Are these the "phantom pins" 1-5 & 14-17 on the CHT/EGT connector?

    Are there aux inputs (other than switches) which can be user-configured for something like this?

    Highest Regards,

    Noah Forden
    RV-7A
    Rhode Island
    Last edited by NoahF; 03-06-2010 at 05:03 PM.

  4. #4
    Am planning one or two auxiliary temp sensors firewall forward as fire sensors. Searched the archives and this is the closest thread.....!!!!!!!!!!!!
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  5. #5
    We don't really have any spare temp inputs designed to be used as a fire sensor.

    You could use the Carb temp input if you are fuel injected. If you are using the Dynon ADAHRS it has its own OAT so technically the EFIS would have a spare OAT input that could be used if we changed the software.
    Rob Hickman
    Advanced Flight Systems Inc.

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