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Thread: Help Needed

  1. #1
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    Help Needed

    Dear All,

    Thanks for reading this but i need a little help.

    Im doing a "drop test" from 200ft and when the drop frame hits exactly 50ft i have to sequence some servos before it lands. I have a couple of small RC sequencers but do you have any idea what type of SIMPLE altimeter i can use that i can preset to start the sequencer at 50ft? It needs to be very accurate.

    Thanks in advance.


  2. #2
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    Help Needed

    Quote Originally Posted by Kestrela View Post
    Dear All,

    Thanks for reading this but i need a little help.

    Im doing a "drop test" from 200ft and when the drop frame hits exactly 50ft i have to sequence some servos before it lands. I have a couple of small RC sequencers but do you have any idea what type of SIMPLE altimeter i can use that i can preset to start the sequencer at 50ft? It needs to be very accurate.

    Thanks in advance.
    All of the rocketry altimeters “arm themselves”, meaning they zero their initial setting when the rocket they’re riding within launches. All altitudes measured and used to trigger events are relative to that zero elevation.
    What you’re discussing is something that actually measures its current altitude based on detection of the actual ground and triggering at a precise distance above it. None of the rocketry altimeters that I know of will do that. With some reprogramming you might be able to get one of the Altus Metrum (open source) devices to set zero when released at 200 feet and trigger at -150 feet from that.
    The most accurate way to do this would be with a proximity or position sensor constantly measuring distance to ground and triggering at 50 feet.

    Steve Shannon
    L3CC, TAP,
    President, Tripoli Rocketry Association

  3. #3
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    The Eggtimer Classic and Eggtimer Quantum both support PWM servos natively. The deployment altitudes only go down to 100', but we can probably take care of the 50' requirement for you... especially with the Quantum because there's tons of available memory for enhancements. Drop me an email, support@eggtimerrocketry.com

  4. #4
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    Quote Originally Posted by Steve Shannon View Post
    All of the rocketry altimeters “arm themselves”, meaning they zero their initial setting when the rocket they’re riding within launches. All altitudes measured and used to trigger events are relative to that zero elevation.
    What you’re discussing is something that actually measures its current altitude based on detection of the actual ground and triggering at a precise distance above it. None of the rocketry altimeters that I know of will do that. With some reprogramming you might be able to get one of the Altus Metrum (open source) devices to set zero when released at 200 feet and trigger at -150 feet from that.
    The most accurate way to do this would be with a proximity or position sensor constantly measuring distance to ground and triggering at 50 feet.
    Thanks Steve,

    I had looked at a drone controller with a laser range finder fitted to it but the programming and setup would take quite some time. I was hoping some rocketry electronics already existed that may be better suited.

    Regards

  5. #5
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    Quote Originally Posted by Kestrela View Post
    Thanks Steve,

    I had looked at a drone controller with a laser range finder fitted to it but the programming and setup would take quite some time. I was hoping some rocketry electronics already existed that may be better suited.

    Regards
    If I were you I would immediately PM Cris Erving (cerving above) to see what he can do to help you. He’s very clever and has a very nice line of Rocketry electronics.
    Steve Shannon
    L3CC, TAP,
    President, Tripoli Rocketry Association

  6. #6
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    Quote Originally Posted by Steve Shannon View Post
    If I were you I would immediately PM Cris Erving (cerving above) to see what he can do to help you. He’s very clever and has a very nice line of Rocketry electronics.
    Email already sent. Thanks Steve

  7. #7
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    Quote Originally Posted by Kestrela View Post
    Email already sent. Thanks Steve
    Good luck! Please let us know how you solve this. Are you dropping this from something that is flying or a static platform attached to a tower, or what?
    Steve Shannon
    L3CC, TAP,
    President, Tripoli Rocketry Association

  8. #8
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    Quote Originally Posted by Steve Shannon View Post
    Good luck! Please let us know how you solve this. Are you dropping this from something that is flying or a static platform attached to a tower, or what?
    Its being dropped from a tower to test and dial it in, then it will be dropped from a helicopter.

    Regards

  9. #9
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    Quote Originally Posted by Kestrela View Post
    Its being dropped from a tower to test and dial it in, then it will be dropped from a helicopter.

    Regards
    Does it have to be self contained or can it be triggered externally?
    Steve Shannon
    L3CC, TAP,
    President, Tripoli Rocketry Association

  10. #10
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    Quote Originally Posted by Steve Shannon View Post
    Does it have to be self contained or can it be triggered externally?
    Self contained im afraid...would of been simple if it wasn't

  11. #11
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    I'd be careful, a lot of this depends on decent rate, waiting till 50' indication to deploy or activate something is pretty low in my experience, if you watch a lot of the deployments with chute release there seems to be a pretty good range of actual release even when set at 500'.

  12. #12
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    Quote Originally Posted by burkefj View Post
    I'd be careful, a lot of this depends on decent rate, waiting till 50' indication to deploy or activate something is pretty low in my experience, if you watch a lot of the deployments with chute release there seems to be a pretty good range of actual release even when set at 500'.
    We actually deploy a chute higher than 50ft but we need to accurately measure its height so that at 50ft something else happens on the frame

  13. #13
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    Quote Originally Posted by Kestrela View Post
    We actually deploy a chute higher than 50ft but we need to accurately measure its height so that at 50ft something else happens on the frame
    Ok what is your decent rate, if in the 20fps range maybe it isn't as critical since you have some margin/delay.

  14. #14
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    Quote Originally Posted by burkefj View Post
    Ok what is your decent rate, if in the 20fps range maybe it isn't as critical since you have some margin/delay.
    We are using a iris ultra 60" chute so that handles 19lbs @ 20fps. We are slightly below that weight.

  15. #15
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    If you need the 50 ft. trigger to be very accurate and since you will be under chute and have a know orientation as you drop, I would very seriously consider the altitude range finders used in drones. I've never checked, but are the units available as separate units instead of integrated into the drone already? If so, it shouldn't be too difficult to integrate into your unit.

    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

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