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Thread: All-electric simulated machine gun?

  1. #21
    cluttonfred's Avatar
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    Perhaps an Arduino-based solution like this could be used to drive a solid state relay for the flash and also run the sound component? http://arduino-info.wikispaces.com/ArduinoPower

    I can't offer much more than moral support, Ron, but I am cheering for you!
    Last edited by cluttonfred; 02-25-2013 at 04:58 AM.
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  2. #22
    rwanttaja's Avatar
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    Quote Originally Posted by Matthew Long View Post
    Perhaps an Arduino-based solution like this could be used to drive a solid state relay for the flash and also run the sound component? http://arduino-info.wikispaces.com/ArduinoPower

    I can't offer much more than moral support, Ron, but I am cheering for you!
    Well, at least I'm having fun. It's been about twenty-five years since I last soldered parts onto printed circuit boards. Spent a bunch of time finding my old pencil soldering iron with the teeny-tiny tip. Obviously, way out of practice...the flasher circuit didn't work until I wiggled the power transistor. But I also got to let the magic smoke out, then made a Saturday-evening trip to the mall to go to Radio Shack for some replacement parts. Just like the good old days.

    The Arduino system is interesting. It'd be fun to pick up one of the experimenter packages and fiddle with it. My last attempt at using a microprocessor to control external hardware was trying to build an adaptor board to work Christmas lights with my VIC-20. It Did Not End Well for the computer. The user community around the Arduino looks like they've got some great ideas.

    However, I don't think it's the best solution for this problem. It's got a sound playback option, but I didn't see any waveform-combining or similar functions.

    But...it did give me an idea. There are a lot of good sound editing packages on PCs. Seems like it'd be easy to build the right sound on a PC and duplicate it so you have 30 minutes or an hour of shooting.

    Why so long? Simple: Because we're going to use a Smart Phone (or an IPod) as the playback device. Transfer the sound to the device, then, just before you take off, start it playing. Set the file to repeat, if you like. Have your trigger switch just connect the output of the smart phone to your amplifier system.

    Note this lets you "change guns" whenever you like. Load any number of sound files, for any type of gun. Put "Hitler's buzzsaw" on your FRED.

    OK, now what about the flash?

    I used a common 555 timer chip in the "astable mulivibrator" mode to generate the series of pulses in my video. I was just the IC with two resistors and two capacitors. However, the 555 also has a monostable mode...if the voltage at one pin exceeds a given value, it causes the 555 to issue just one pulse.

    So... in addition to the amplifier, we can feed the headphone output of the smart phone into a small half-wave rectifier, consisting of just a diode, a resistor, and a small capacitor. The rectifier converts the sound to quickly-varying DC...and when the DC gets high enough (like a big pulse when the gun fires) the 555 goes active for what ever time we wish...let's say 1/10th of a second.

    The 555 could drive a solid state relay, but being a solid state device, it's going to have some resistance loss that'll reduce the voltage to the high-intensity LED. I'm also a bit cautious about SSRs just because I have no experience with them... they're used mostly to control high-voltage AC circuits from computers.

    So we can just use that same old power transistor setup I had.

    But what about the low voltage it was providing the LED? Silly rabbit... why are we fixated on using 12 volt power to start with? Why not use two six-packs of AA batteries and run the thing from 18 volts. That gives plenty of extra room to power the high-intensity LED decently. "Head Spacing" if you will.

    Even if you do have a 12V battery onboard (you'll need it for the amplifier) you can add a two-pack of C cells and get the gun power up to 15 volts for the gun electronics... still enough head spacing.

    So... I'm thinking my wife's Ipod is going to disappear in a day or so....

    Ron "Five drops of sinister sauce" Wanttaja

  3. #23
    rwanttaja's Avatar
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    Quote Originally Posted by rwanttaja View Post
    But...it did give me an idea. There are a lot of good sound editing packages on PCs. Seems like it'd be easy to build the right sound on a PC and duplicate it so you have 30 minutes or an hour of shooting.
    Try it out? Of COURSE I had to try it out:

    http://www.bowersflybaby.com/combined.mp3

    I found a Mosin Nagant audio clip online, cropped it down to 0.5 seconds (it was pretty quiet by that point), duplicated it for 20 seconds, then duplicated the track twice with ~0.16s offsets each time. This gives us an effective rate of fire of about 360 rounds per minute.

    Ron Wanttaja

  4. #24

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    I'm very intrigued with the LED, particularly if it can be powered by six AA batteries!I'm afraid of the weight of a sound system, though. Might have to settle for yelling BANG BANG.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  5. #25
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    Quote Originally Posted by Frank Giger View Post
    I'm very intrigued with the LED, particularly if it can be powered by six AA batteries!I'm afraid of the weight of a sound system, though. Might have to settle for yelling BANG BANG.
    The LED I've been fiddling with is a 12 volt unit, so we'd need at least eight cells. I'm thinking two six-cell holders to run the thing with 18 volts, and limiting the voltage that actually reaches the LED.

    Don't know how long AA cells will last, but how often does one expect to be actually firing the thing? "Bricks" of AA batteries are cheap at places like Costco or Sam's Club. For those of a greener persuasion, 12 NiCads would still give 15 volts, plenty for the application.

    Ron Wanttaja

  6. #26

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    Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  7. #27
    rwanttaja's Avatar
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    Quote Originally Posted by Frank Giger View Post
    Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload.
    So, AA batteries for you, then. Or should we call them, "Archie" batteries? :-)

    Ron Wanttaja

  8. #28
    rwanttaja's Avatar
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    Quote Originally Posted by Frank Giger View Post
    Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload.
    To go serious for a moment, I'm always amazed at how LITTLE ammunition fighters carry. That 47 rounds equates to about 12 seconds of firing. Yes, you carry extra drums, but there's no way you're going to change them in combat. And the P-51D had six .50 cal machine guns, each loaded with 400 rounds, and each gun shooting at 800 rounds per minute. How'd you like to fly to Berlin and back in 1944 with only 30 seconds of firing time?

    Ron Wanttaja

  9. #29
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    You think that's bad, how about the Hawker Hurricane IIC and other British planes that used the early Hispano 20mm cannon with 60 round drums? Some of the bigger aircraft like the Beaufighter had a second crewman who could load new drums, but not the single-seat fighters. At 600-850 rpm that meant that the Hurri only had 4-6 seconds of ammunition, 8-12 if only two cannon were used at a time. Later Spitfire, Tornado and Tempest fighters had belt-fed Hispanos with twice the ammunition capacity.

    From my virtual experience in online flight simulators, however, I can say that it's not necessarily a problem. You learn to hold your fire until you get the shot, and when you do, it only takes a short burst of 4 x 20mm to finish the job.

    Quote Originally Posted by rwanttaja View Post
    To go serious for a moment, I'm always amazed at how LITTLE ammunition fighters carry. That 47 rounds equates to about 12 seconds of firing. Yes, you carry extra drums, but there's no way you're going to change them in combat. And the P-51D had six .50 cal machine guns, each loaded with 400 rounds, and each gun shooting at 800 rounds per minute. How'd you like to fly to Berlin and back in 1944 with only 30 seconds of firing time?

    Ron Wanttaja
    Last edited by cluttonfred; 02-28-2013 at 02:24 AM.
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  10. #30

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    The other side is Rene Fonck, who shot down three planes using only seven rounds.

    Then again, he used to practice gunnery by shooting rabbits with a rifle while driving a motorcycle.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

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