Questions about my DIY Launch Controller

Discussion in 'Ground Support' started by Brainlord Mesomorph, Apr 8, 2018.

  1. Apr 8, 2018 #1

    Brainlord Mesomorph

    Brainlord Mesomorph

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    Still in the design stage of my launch controller. I’ve picked out my box, (A lunchbox sized Pelican Case) it has plenty of room for a cool control console, and a 12 volt lantern battery (but I don’t think that’s the right battery anymore). But then, I get greedy with the feature set. And I think I need the help of an EE.

    I understand the basic circuit (since I was 12), (battery, key switch, light, momentary contact switch, wire, gator clips, - got it) I can make that. But I do have a couple of questions about component selection:

    1. 12VDC 10amp components, right? So like a motorcycle or lawnmower key switch?

    2. What’s the *right* wire to use for an E-class controller? (able to handle the voltage, but not too much resistance in 30 feet?)

    3. What’s the right battery to use? Again I’m thinking E class, or maybe even clustered launches or multiple pads. But this gets into my feature-creep problem. Which I’ll get to next.

    So, then I start to think of cool features I could add, but only if they are cheap and easy:

    A flashing continuity light? A beeping and flashing continuity light? Do I understand if I put this motorcycle turn signal relay: https://www.ebay.com/i/222730589660?chn=ps in the continuity light circuit I’d get beeping and flashing?

    A countdown LED ?? That would very cool!

    I’ve been looking at various LED clocks and/or timer kits, like this: https://www.newfrog.com/product/dc1...imer-digital-led-dual-display-0-999-mi-191153 But that’s a relay that can control a device – (like launch the rocket for me – NOT what I want to do), and it has its own little tiny start button, I would prefer something like just a large two-digit ten second countdown that starts when you flip the keyswitch. Could that be easily done by a layman? Or should I just give up on that idea (maybe I’ll put a clock in the corner)?

    Battery level indicator? How much power would that use? (I see digital voltmeters for like 2 dollars, or is that a different thing?)

    Now please explain about battery choice and capacity.

    Like I said, I have room for a lantern battery. I want the capacity for a long day of e class launches, maybe clustered launches. (not that I’m doing that yet, I just want to be able to). I will also be adding the Eggfinder RX unit to the box, so we need to power that.
    Rechargeable would be nice. What circuitry would be needed for recharging? I don’t want to take it out and put it in a charger.

    But that has me thinking (and here feature-creep sets in) if I’m carrying a large rechargeable battery out to the middle of a field… my laptop battery sucks, especially if it’s running two webcams at once. Could the Launch Controller power the laptop? (12 VDC Out?) Could I recharge my phone from it? (USB charging out?) How about a small fan, it gets hot out there.

    So that’s the questions I have that require an EE:

    How much power do I need for the launcher and eggfinder?

    How much power can I carry in a lunchbox size container (and for how much money?)

    And what could I do with that power? (as in accessories like the laptop, I was kidding about the fan)


    As always, any help appreciated
    Thanks guys!
     
  2. Apr 8, 2018 #2

    karlbaum

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    I use a car jump start battery near the launch pad with 14 gauge leads. I use a relay circuit to control the launch circuit. The control circuit uses cat 6 network cable which can be run over 1000 feet.
     
  3. Apr 8, 2018 #3

    sghioto

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    I'm pretty sure that turn signal relay will not work correctly in this situation they require too much current, there are other ways to achieve this. As far as the power supply needed from all you have listed I would invest in one of those portable 12vdc battery packs rated 15 or more amp-hours.
    EDIT: For 30 feet of wire to the pad would require a minimum of #16 gauge cable. A lot of guys use extension cords for this.
    SG
     
  4. Apr 8, 2018 #4

    Brainlord Mesomorph

    Brainlord Mesomorph

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    Hold on guys, I think we're talking at different levels:

    I used to launch rockets w/ a 6 volt lantern battery that today costs $6
    The Estes Class E controller uses 4 AA batteries. (EDIT: and that wire is heavier, but is definitely not a 120V extension cord)
    UPS batteries, is that 6Volt 7amp hours? $10 each (I was thinking like two of those or so)
    I have a USB phone charger that fits in my pocket, charges my phone 4 times and cost $30.

    OTOH:
    A car jumpstarter costs $70. (do need enough power to start a car?)
    And is the other guy talking about a $120 battery?! (and that needs a handtruck?)

    I'm not going camping, I'm spending an afternoon setting off Estes ignitors.
     
  5. Apr 8, 2018 #5

    LithosphereRocketry

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    What you describe is definitely Arduino territory.

    The relay won't give you a flashing light on its own- it's just a switch - literally an electromagnet that flips a lever.

    For batteries, I recommend a "gel cell" like this one:
    https://www.amazon.com/Sealed-Rechargeable-Battery-Security-Alarm/dp/B007Z462S8

    Capacity shouldn't really matter too much, but I would say go for a lead-acid type battery- they're orders of magnitude ahead in terms of power output. I get that it's overkill, but it works, and works immediately every single time.

    The Eggfinder RX whould be able to handle 12V just fine- it should be a matter of hooking up the + and - to their corresponding battery terminals.

    Charging a laptop might be a challenge - real computers take a lot of power. A phone might be doable if you hook up a USB regulator of some kind - I'm sure someone sells them.

    If you want the countdown and everything, you'll almost definitely need some kind of "smart" electronics - an Arduino would do it. However, you'd need high-power MOSFETs and all sorts of other things to be able to dump that much current. It would be much easier to just use mechanical swtiches and a continuity LED and ditch all the digital electronics. If you want to go the digital route, though, I'm not stopping you.
     
  6. Apr 8, 2018 #6

    sghioto

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    Sure if you only want to launch rockets but you were asking about powering laptops with webcams and such.
    SG
     
  7. Apr 8, 2018 #7

    MikeyDSlagle

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    You can grab one of these batteries

    And one of these:
    12volt outlet strip

    I put a setup like this on my daughter's Radio Flyer. We can run small fans and charge cell phones and tablets, we even ran a portable DVD player from it. Should be plenty of juice for ya. But not to charge a laptop. It definitely would but not very well.

    I put a an on/off switch between the battery and the USB and a momentary push button switch for the volt meter. Just so I could isolate everything.

    You'll need a charger for the battery. You can easily modify the charger to plug into the side of the case so you never have to open it. You could really simply put a cigarette lighter plug the charger, the male end, and plug it into the socket.

    I had ideas of flashing and beeping things for my controller as well. Double pole switches and relays can be used to activate such things with little risk of setting off the motors. Not all that difficult to achieve. I could never get my beeper circuit to work correctly so I scratched the whole idea.

    Other battery options would be a R/C power pack, smaller and lighter but not as much runtime.
     
  8. Apr 8, 2018 #8

    Brainlord Mesomorph

    Brainlord Mesomorph

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    Thank you.

    The DC strip is out of budget.

    Your the 2nd person to recommend that battery.

    Re Flashing: how bout this: https://www.ebay.com/i/231681790585?chn=ps&dispItem=1

    Re Charging (get it?) how bout: https://www.ebay.com/i/112363136919?chn=ps&dispItem=1
     
  9. Apr 8, 2018 #9

    Brainlord Mesomorph

    Brainlord Mesomorph

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    Actually the question was: "could it be done cheaply in a lunch box sized container?"
     
  10. Apr 8, 2018 #10

    Brainlord Mesomorph

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    (sigh)

    I'm a "computer guy." My current "BAR" status is a result of my attempt to find something *else* to do. Something "real" that involves "going outside."

    I'm sure if I stay here long enough, my rockets will someday involve autonomous recovery systems that use GPS and inertial guidance to fly themselves back to land my feet (while I look the other way and drink) and my NextGen Ignition Control Systems will involve launching rockets with a mouse, or just by voice control.

    But that is not today.

    EDIT: Right now my goal is just for my niece and nephew to feel very excited when they get to turn the key to the ARM position and open the panel over the LAUNCH button.
     
  11. Apr 8, 2018 #11

    sghioto

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  12. Apr 8, 2018 #12

    MikeyDSlagle

    MikeyDSlagle

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    Oh. As for the switch. My homemade launch controller uses an ATV switch. Heavy duty and costs like 7 bucks online.

    You can grab small voltage meters for a few bucks as well.
    For powering external devices, a simple 12 volt outlet aka cigarette lighter socket will work well enough.

    That "charger" is not a charger. It is a charge controller. Goes between a cheap wall transformer charger and the battery to keep the battery from overcharging. You want an automatic charger. A cheap example here

    Bells and Whistles:
    The timer you referenced could work. I would have it on a separate circuit than your firing circuit if it is just for coolness. Wouldn't want it on the continuity circuit either. Have a switch that turns on your timer and flashing lights. You could use the same battery but may need a small inline power supply to step down to an acceptable voltage, or use a separate power source such as 2x AA batteries. Don't know if the timer has a memory or not so you may have to program it on the spot for countdown. You wouldn't need anything on the relay circuit if you just wanted the timer. But a large green light may be a good idea. Timer expires, green light comes on, kiddos press the launch button.
    A sequential timer would be neat. Think drag racing but with LEDs. Three reds, one amber and one green.
    A chirping circuit could also be activated with the same switch. Maybe search for electronic chirper or electronic cricket.
    Set you one of these by your pad. :)

    So:
    Turn key on sending power to two separate circuits: A firing circuit and a timer, cricket, flashing lights circuit. The timer comes on but doesn't count down.
    A momentary switch to test for continuity. A beeper and LED could be put in this circuit. Good continuity, you get a beep and a light.
    Press a button (push on, push off) activating the countdown.
    Countdown expires, a green light comes on kiddos press the launch button.
    Rocket lifts off and everyone is happy.

    Mikey D
     
  13. Apr 9, 2018 #13

    Handeman

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    Well, if a $17 strip is "out of the budget" then you probably won't get much in the way of bells and whistles. Just like a new car, features = $$$.

    You can reduce the cost if you can do some EE and design some circuits using parts in your "stash". If you're not a pack rat and don't have a "stash" then you're pretty limited.

    I have a simple launch controller in an electronics box about the size of a single receptacle box. It has a 6' length of 16ga lamp cord with clamps for attaching to the battery (open your hood and use your car battery if you want), and 44 ft of 16 ga lamp cord with clips for the pad end. (I bought 50 ft of lamp cord). There is a phono plug and socket as the removable key, a momentary toggle switch, 360 ohm resistor and LED for continuity, a momentary toggle switch for arm that has to be held ON when the momentary Launch push button is pushed to launch the rocket. The whole thing wraps up in a round bundle of cables and is no worse to handles then a coiled 50' extension cord.

    If you want to add bells and whistles to that, that's where the EE comes in. You will need a circuit similar to the 2 transistor multivibrator (http://www.technologystudent.com/elec1/dual1.htm) to make flashing lights or the right timing signal for your countdown circuit.

    If you define exactly what you want, I'm sure there are many better qualified EE folks here that can help you. Just remember, the more features, the more components, and they all cost a little more money.

    Good luck and let us know what you settle on.
     
  14. Apr 9, 2018 #14

    sghioto

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  15. Apr 9, 2018 #15

    Brainlord Mesomorph

    Brainlord Mesomorph

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    "Of you define exactly what you want..."
    That's what I'm trying to do.
    OK- forget the timer. Its superfluous.


    if a $17 strip is "out of the budget"...
    Just that the plugs themselves are a buck each, and at the time I didn't think I had the juice for it.


    2 transistor multivibrator
    That would be this, right? https://www.ebay.com/i/400985396241?chn=ps&dispItem=1
    99 cents free shipping :)
    I think if i add a piezo to one side it'll beep


    Batteries
    I found a similar 12V 7AH sealed lead battery for $10 :) (https://www.ebay.com/i/112443246473?chn=ps&dispItem=1)
    My box will carry 2 of them!
    In parallel that's 12V 14AH.
    My laptop battery is 10V 4.4AH

    I think that means I can run the laptop for most of a day using a quarter of my batteries. (it would be half of one battery which is too much) so my "12VDC Out" socket is back on the feature list. :)

    Wire:
    I'm pretty certain that 120VAC "lamp cord" or extension cords is the wrong wire to use (sorry). All wire introduces resistance to a circuit. Thicker wire = more resistance (which may be why you guys need so much power) Look at the transformer for your laptop; notice the difference between the wire that goes from the wall to the transformer (120V) and the wire that comes out of the transformer and goes to the laptop (12V). That's the wire I think we need. I just don't know what to call that.

    @MikeyDSlagle
    That trickle charger is perfect. It even looks like there are screws in the back, I can just open it up and take the guts out. :)
     
  16. Apr 9, 2018 #16

    Steve Shannon

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    No - thicker wire does not add more resistance.
    Thicker wire has less resistance.


    Steve Shannon
     
    Last edited: Apr 9, 2018
  17. Apr 9, 2018 #17

    Brainlord Mesomorph

    Brainlord Mesomorph

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    Hi Steve, you're absolutely right.

    I've just spent a head-spinning 45 minutes on wiki, which only confirmed for me that I don't understand anything about electricity. It does make sense, a thin wire will burn out because of heat which is caused by resistance. But that that seems to fly in the face of the wire in the 12 volt side of your transformer being so much thinner than the 120 V side. Or how modern micro electronics work on such low voltages. My head hurts.

    I love learning new things, but I hate being wrong in front of a bunch of strangers on the internet.
    So, thanks for that... both literally and sarcastically. LOL

    So does that mean the big orange extension cord *is* the right wire?

    And having schooled me on that, am i right about my other assumptions?
     
  18. Apr 9, 2018 #18

    Steve Shannon

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    The wire on the 120 volt side is just a generic power cable, purchased at low cost. It carries less current than the 12 volt wire but technically must be insulated better for the higher voltage.
    The 12 volt side must be capable of carrying more current, but doesn’t need as much insulation.
    Every one of us makes a mistake or more online. The nice thing is that five minutes later it’s flushed from short term memory.


    Sent from my iPhone using Tapatalk
     
  19. Apr 9, 2018 #19

    LithosphereRocketry

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    The one concern I would have about charging your laptop is power regulation. I don't know about yours, but my laptop charger says 20V at 4.5A max. 20V can't easily be gotten out of a 12V battery (without transformers and/or DC-DC converters) and 4.5A is a lot to be regulating- I wouldn't trust anything important with raw battery power. If your computer takes 12V in, you still need to regulate it to insulate against battery imperfections, which typically requires an extra 1-2V "spare" for most regulators. You'll also have a hard time finding a reasonably priced regulator that can supply more than 1-2A, and you'll want big capacitors on either side as well to help the regulator out.

    It's possible all of the above can be found as one unit, but I'm guessing it won't be cheap.

    On the subject of wires, my controller uses all household hardware with 12- or 16-gauge extension cords as the pad cords- mainly so it's modular and easily replaced/extended. You can fly a complex H flight with no L1 and no waiver if you keep it in the low range, so make sure you plan ahead in terms of setback distance - 200ft according to the NAR HPR safety code. I usually just use two 25ft outdoor extension cords with 5ft alligator clip extensions, but I can just add in more on the spot if necessary.
     
  20. Apr 10, 2018 #20

    Brainlord Mesomorph

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    That's the maximum output of the transformer, which will be just less than the max input the computer can take. What does the battery say?

    PC's and laptops have built-in power conditioners (you think the juice coming out of your wall is clean?), as for the laptop, we plug those things into car cigarette lighters! (A car's "12 volt" system is anything but! ) I might not have enough juice to charge the laptop, or it might suck the battery dry. I'm prepared for that. Not enough juice, it just won't work, too much, and I'll pop a fuse, but I think that's the worst that can happen.

    On the topic of wire:
    I think I have found *the* actual, professional, correct, wire to use do for this type of application. :)

    "XLR" cables and connectors. It looks like a heavy 3-pin din, you'll probably recognize it as a microphone cable.

    They're not just used in PA systems, in theater they're also used for the lighting, winches and motors (lifting curtains, etc) . All that stuff backstage is 12 or 24V DC, and all of it is running on wires just like mic cables. (ask any roadie) Its also used in other pro DC applications, on boats, recharging motorized wheelchairs, maybe your high school gym had some DC equipment with these connectors. There are 3, 4,5 up to 7 pin arrangements. The 3 pin will work for me nicely (I actually have an idea that requires an extra wire to the pad). When pros need to send 12 volts 200 feet, they use an XLR cable. I think its like 20 gauge w/ a thin flexible insulator.

    I found a 25 foot cable for $7. I'll let you know how it works.

    So I've settled on my feature set.

    All the parts are on order. I think I've spent about $60 :)
    (I had the Pelican Case)

    But:In order to do that, I had to buy the very cheapest one of every part I needed. And had to use exclusively free shipping. Which means all of these components are now, literally, on several different slow-boats from China. I'll be getting envelopes over the next 6 to 8 weeks, with a button here... a switch there... by June I should have it all.

    Thanks for all the help guys!
    Anyone want to see the WIP control panel design?
     
  21. Apr 11, 2018 #21

    sghioto

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  22. Apr 12, 2018 #22

    Brainlord Mesomorph

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  23. Apr 13, 2018 #23

    sghioto

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    That's going to look great, very professional. What about adding a switch to be able to arm all three pads for drag racing?
    SG
     
  24. Apr 13, 2018 #24

    W7AMI

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    Don't know about the better part but how about these?

    https://www.frontpanelexpress.com/front_panel_designer/the_idea/
     
  25. Apr 14, 2018 #25

    Brainlord Mesomorph

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    BRILLIANT!

    Now the question is: do I get rid of the OFF position or by a 6 position switch?

    that's 99 cents!

    :)
     
  26. Apr 14, 2018 #26

    Brainlord Mesomorph

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  27. Apr 17, 2018 #27

    Brainlord Mesomorph

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    OK Now I have this schematic/block diagram:
    [​IMG]
    But I've noticed that a couple of things that I'd like to to happen when I push the Ignition button ("Commit" status light and constant piezo tone) will also happen on the continuity test. (Although with a 350 ohm resister in the circuit, it will like a low tone and a dim light... can an LED be dim?)

    Any ideas on that?

    (and I thought there were supposed to be EEs camping on this forum. I don't think I've heard from one)
     
  28. Apr 17, 2018 #28

    Reinhard

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    Some quick notes:
    1) Most LEDs don't contain a current limiting resistor. Regular LEDs can't be operated this way
    2) Things are connected in series, that don't make much sense this way. Anything connected in the string the "Continuity Test Ready LED" over "Flashing Unit" to "Status LED Commit" needs some rework.
    3) Lots of redundant switches and LEDs. Most LEDs functions don't match their names. That's fine if you like to play with switches and LEDs but it can reduce reliability and will make it more complex to use.

    1) und 2) need to be changed to make the circuit functional. 3) is more a question of personal taste.

    A higher resistance value will limit the current and therefore make the LED less bright. As mentioned above, this resistance is actually needed. The other LEDs in your circuit will be much brighter but only for a very short time. ;)

    Reinhard
     
  29. Apr 17, 2018 #29

    Brainlord Mesomorph

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    1. I see that now, how many Ohms do I need on those?
    2. More things in parallel? (more little loops?) I can do that.
    3. Names not matching up? b/c most LEDs are "what to do next" lights, Turn the key to Arm and the "Continuity Test Ready" light comes on because its next. (Yes redundant but fun) And the "Status Board" is completely unnecessary. :)

    THANKS!

    EDIT: the 65-in-One Kit I had in 1978 didn't have LEDs.
     
  30. Apr 17, 2018 #30

    Brainlord Mesomorph

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    oops (double post deleted)
     

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