Launch panel innards

Discussion in 'Ground Support' started by caveduck, Mar 16, 2019 at 10:15 PM.

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  1. Mar 16, 2019 at 10:15 PM #1

    caveduck

    caveduck

    caveduck

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    A rare look at the back of the hardwired DART launch controller, near the end of its 3rd year of service. Just upgraded to an SSR from the original mechanical relay, which was starting to get flaky after several thousand flights. No electronics other than the SSR and the LED indicator lights.
    224A34AE-B659-4BF1-9986-86D5051B7397.jpeg
     
  2. Mar 17, 2019 at 4:19 AM #2

    sooner.boomer

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    Got schematics for that? Local club is looking for a new controller.
     
  3. Mar 17, 2019 at 5:01 AM #3

    caveduck

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    I don't have a drawing of it, but the circuit is actually just that of a very simple launch controller, but with a 20x fanout for selectable pads. It uses a relay to short out the continuity light rather than dumping all the current through the firing button, which would have been the weak link in the chain for current carrying capacity.

    Here's an Autocad layout of the front panel, will post a photo after I dig one up.
    DART SE-520 ACAD layout.jpg
     
  4. Mar 17, 2019 at 1:53 PM #4

    Exactimator

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    28235740_1985443671469120_7572919138028329933_o.jpg Here's a pic of the front.
     
  5. Mar 17, 2019 at 3:44 PM #5

    HonestJohn

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    So could you give a brief tutorial of how the controller operates for us neophytes? I've never actually been to a club launch...:eek:
     
  6. Mar 17, 2019 at 3:59 PM #6

    Glasspack

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    I could build a schematic for that one if anyone is interested …..Let me get started on Digikey
     
  7. Mar 17, 2019 at 4:03 PM #7

    Glasspack

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    Did you build that Cave duck ?? Looks very nice
     
  8. Mar 17, 2019 at 4:17 PM #8

    Glasspack

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    I built one but only for 4 pads...… High Power and low power model rockets

    looks like the same style Pelican case.
     

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  9. Mar 17, 2019 at 4:29 PM #9

    cwbullet

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    That is pretty nice.
     
  10. Mar 18, 2019 at 7:17 AM #10

    caveduck

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    @Glasspack - yes I built the DART panel. Here is the schematic as promised...drew it up hastily in OmniGraffle. I had a bill of materials from the planning phase but looked it over and it doesn't represent the as-built very well so I'm not posting it.
    @HonestJohn - TLDR operation tutorial:
    Toggle switches are pad selectors
    Insert key and turn on key switch - power light comes on.
    Flip up arm switch cover and turn on switch underneath - "arm" light comes on and continuity LED will light if you have continuity
    Press "Fire Missiles" button to launch

    Parts - case is a Seahorse 520 (Pelican clone). There are no case penetrations so it's water- and dust-tight. Get a good key switch (I used Eaton) and an SSR. We wore out a vanilla mechanical auto relay in several thousand launches. Use E-Switch or Eaton toggles from Digi-Key. Cheapo switches will not have the life. We did use 1/4" plugs/jacks from the Amazon 20-packs. You have to solder the center stack of the plug since from the factory they are just crimped and go flaky right away, but after doing that they have been solid for 3 years. Battery life is amazing...we can do 1000 flights on 50% charge of a 3 Amp-hour LiPo.

    Planned upgrades:
    * brighter LEDs - the ones we have are not too good in sunlight
    * add piezo "armed" buzzer in parallel with the arm LED
    * (maybe) change power inlet connectors to PowerPole
    * Change toggles 16-20 to spring return momentary for MPR/TARC pads to disallow multi-select
    DART_launch_controller_schematic_2016.jpg
     
    Last edited: Mar 18, 2019 at 7:26 AM
  11. Mar 18, 2019 at 11:37 PM #11

    Glasspack

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    20-Pad-Controller-1.jpg is this pretty accurate ? this is one I put together from the photos...……using Digikey software Before you posted your schematic from OmniGraffle
    And also I didn't see a continuity LED on the Panel …..
     
  12. Mar 19, 2019 at 4:44 AM #12

    caveduck

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    Close :) BTW the continuity light is the one above the "fire" button in the photo. The one thing I see with your version is that once the arm switch is on, you have +12VDC on one clip of every selected pad with no resistance in the way, so large current will flow if that clip manages to touch anything else that is grounded, even to earth. In my circuit the continuity light and relay are on the hot side so that no DC+ reaches the pad until the launch button is pressed; you can ground either or both of the clips at the pad - even if the pad is selected - and nothing bad will happen. Only the ~20 mA continuity current will be carried to the ground.
     

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