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Thread: Proof of concept

  1. #1

    Default Proof of concept

    After working through the initial product requirements, we built a proof-of-concept using mostly off-the-shelf parts when able. Actually, we built two of them - one for the lab and one for the plane. The intent was to validate the overall idea and learn what we didn't know at the time.

    Well, it turns out the flying experience was great, which is of course why we went on to build the real thing.

    We also learned a lot about the user interface. The original idea didn't have a switch panel. We added that when it became clear the you want to have instant control a few things. Turns out you don't need to have instant control over everything - just a few key things.

    It also was tied in directly to the p-leads on the mags, meaning it could do an automatic mag check for you. That was a bust. I'd never really noticed it before, but you do use the mag switch more often than you think. And when you do use it, it's usually to check something in the engine when it's not running right. Pretty important. So we added that too.

    We also went to a much better, newer screen.

  2. #2


    Here's the Display Unit for the plane.

  3. #3


    And this one is for the lab...

  4. #4

    Default Moving out to the hangar

    Kevin and Jake during a long day of testing and troubleshooting out at the hangar.

  5. #5

    Default It's installed and running in the plane

    The proof of concept fired up for the first time in the plane!

  6. #6


    And here it is flying... wahoooo

  7. #7
    Join Date
    Feb 2007

    Default I want one!

    This is awesome... I want one! Good work VP!

  8. #8

    Default Proof of Concept Display Unit

    Here's another shot of the Display Unit that went in the plane. We made it using (mostly) PC-104 form factor components. These are useful because you can stack them and assemble different modules as needed. Of course there is no shielding, it's bulky (the production version is only 1.7" deep), and overall pretty crude, but it worked well for its intended purpose.

    We used to make the aluminum POC bezel. This is neat site, and you can download a relatively decent free 3D CAD tool, then make your model, upload it, and a few weeks later your part shows up at the door. Wish I new about it while building my -7. We use SolidWorks for the production version, which is a professional 3D CAD program.

  9. #9

    Default POC DU for Lab

    Here's the unit for the lab (before we tore it apart in the picture way above). It's electrically identical to the DU that went in the plane, and has no bezel. We just fabbed up a plastic frame and stand.

  10. #10

    Default POC Control Units

    The Control Units were quite a bit more work than the Display Unit because we had to figure out how to use the solid-state switches. Also, there is no operating system on the CU (it runs in real time), and so we had to write a lot of the code for serial communications and systems monitoring, in addition to all the other stuff it has to do.

    In the end, we learned a ton of stuff both from lab testing and installing it in the plane, and were able to roll all that knowledge into the production version (which by the way works beautifully).

    One of the things we learned was that we did NOT want to making the wiring more complicated. We had a zillion wires going between the DU and the two CUs. Wiring that in the plane, we quickly realized that there had to be a simpler way. If you now look at the production version, you simply connect the DU and CU(s) with pre-manufactured cables that carry power, ground, data, and a few other things. It literally takes minutes to make those connections on the production version - but it was a real pain in this early version. These pictures really don't illustrate the point, but at least you can compare these with the new "red box".

    You can see there are two PCBs in the Control Unit. One has the power supply, processor, and handles low current stuff like trim motors and position sensor feedback. The other is the high-current board, and provides switching for the 5, 10 and 18A circuits. There are 10 printed circuit board layers between these two boards. Anyway, this design proved to be a good one, and we've used it in the production version. And improved the outside case of course and moved to better connectors.

  11. #11

    Default Switch Evaluation

    After we decided that a Switch Panel was needed, we had to find some good switches. We found some that had red/green LED lights on the tip of the switch. Having color on the tip would allow you tell instantly the status of the device, and the LED color was controlled by the computer.

    Green=on, red=fault, no light=off.

    Anyway, below are some photos of a few switches, and you can see what the red and green LEDs look like.

  12. #12
    Join Date
    Feb 2007
    Blue Ridge, GA

    Default Switches


    It appears you have selected the center switch (black toggle) for the production version, correct? If so, will you be offering these switches for sale? Just want my panel to be consistent. Maybe you can share the switch source? DigiKey, Mouser?
    Bret Smith
    RV-9A Fuse
    Blue Ridge, GA

  13. #13

    Default Switches

    Bret, these switches aren't stocked by Digikey or Mouser, but I think you have a good point about matching.

    The one we use is a logic-level PCB mount version without a bezel. Fortunately, there is a family of switches and we'll order some panel mount that are rated for 6A. That way, you can use them for direct loads or for an external switch to our system. I think they're about $10-$15 each.

    Also, the LED will be in sync with the switch - up is green and down is red. The LED is on separate pins so you decide if you want it lit or not.

    Stay tuned for more details.

  14. #14

    Default Switches are in

    We now have these switches in stock if you want to use them for any additional circuits.

  15. #15


    how do you wire those switch on the VPX pro? I have the feeling that they do not like 12 volts. I am afraid that I kill one today when I was testing them!!

    It is not very clear!

  16. #16


    You need a resistor. Please see here:

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