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  1. #1
    150+ Forum Groupie mach7's Avatar
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    Mechanical engine gauges


    Looking for some technical input. I am planning on building, and installing mechanical engine gauges using stepper motors and programmable microprocessor chips.

    These PIC programs will be controlled by a sliding thrust lever pots. The gauges that I am constructing will be for the BAe146 simpit install and will consist of N1, TGT, N2 and WF (fuel flow) indications.

    Unlike a conventional setup, these gauges will not receive information from FS2004, but rather “parallel” the computer program to indicate simultaneous information.

    In other words…when I set 60% N1 on the mechanical gauges, they should indicate 60% N1 on the FS2004 add-on 146 aircraft program.

    The way I am planning to do this is to have a ‘dual pot’ arrangement for every thrust lever, (4), whereas one pot output goes to the mechanical gauge and the other pot output feeds the computer (MSFS) program for engine thrust operation.

    I might be able to use the same potentiometer for both…still a consideration.

    I think that the only gauge that I will have to really sync up would be the N1.The N1 appears to be the only gauge MSFS looks for when giving the appropriate thrust output for thrust lever angle. TGT, N2 and WF, (mechanical), will follow whatever I have programmed in the chips as they can be quite variable from a thrust setting point of view.

    Anyway, my question is with MSFS thrust lever potentiometers.

    Are all conventional manufacturers using the same type of potentiometer in there thrust lever hardware in order to operate within the MSFS world? When I refer to ‘type’ I am talking about voltage IE: 0 to 5 volts. (I do realize that there are many different types of potentiometers available….rotary…sliding etc).

    In my application I will be using a purchased sliding pots as opposed to ripping apart an exsisting thrust lever box.

    Having said this, I need to know what flight sim is looking at to set thrust from a potentiometer voltage point of view. I need to know the voltage output to flight simulator for every 10% of power (N1) increase/decrease. Armed with this information, I should be able to modify my mechanical gauge program so that it will display the same information.

    Does this sound like a viable plan…or am I wasting my time?

    I would appreciate any imput on this subject.



  2. #2
    2000+ Poster - Never Leaves the Sim Trevor Hale's Avatar
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    Hi Jim.

    Thats where you will find a Book that will describe building gauges.

    If you really want to tackle this task, you need to know that FS, assigns a Number from 0 to 65535 for throttle input. Standart Joysticks input 0 to 5 volts. If you want instruments, I think your best bet is to pick up a servo/stepper motor card from and control your instruments with FS2Phidgets.

    you could do it the way you say, but you would essentially be driving the instrument with the potentiometer position regardless if the engines are running, failed, or fs not even loaded.

    Basically to put it mildly, your doing it the hard way, but if you wana give it a go, then go for it. hook up a pot to fs, and see the values you get.

    Trevor Hale

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  4. #3
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    One thing that would be a backdaw with this. If you have to recalibrate your inputs to FS, you also have to change your parameters for the instruments again. (recalibrate them also). Your idea is good, but I think you will struggle to get this as you think. Much better to interface instruments via fsuipc/simconnect.

    Just my opinion

    Any route you decide to go, I wish you good luck

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  6. #4
    75+ Posting Member
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    Hi Jim,

    I think if I were doing that, I would drive FS with the pots via an off-the-shelf interface card and fsuipc - You can then calibrate up your inputs as required.

    I would then write a little interface app in VB or similar to grab the values back from fs using fsuipc calls and then send them to the micro driving the instrument.

    You can then calibrate the instrument driver to match.

    Means that the fs value is the reference, not the pot voltage which to me is more logical.

    If you understand how USB comms works, I reckon that is the way to go rather than serial because it is faster and the protocol/interfaces exist to integrate with PIC firmware and host code. enabling different instruments to be identified to the host app and treated according to type.

    Don't yet fully understand it myself - But I'm working on it !

    I can recommend Mike Powells book as a great reference too - If you don't have it already that is.

    If you are pretty handy with mechanical/electronic construction, you could save yourself a fair bit of money - So I reckon go for it !

    I would be interested to hear how you get on.



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