All-electric simulated machine gun?

[rwanttaja]

I've worked on this, on and off, for the past couple of weeks. Basic flasher we've got; I've been working on the audio-triggered flash.

Built the color organ, couldn't get it to do what I wanted...think the impulse of the gun just confuses the simple filters.

However, I used the front amplifier from it into the comparator input of a 555-based monostable multivibrator, and got it to work tonight... LED flashes at the rate of the gunfire playing on the smart phone. The flash seemed to skip a bit, now and then, and I thought I had a problem. Until I listened carefully to the sound, and realized the skip was where the audio looped.

Biggest problem is that there seems to be a slight delay...the flash comes slightly after the bang. Gonna look into that a bit more.

Overall, I'm not too happy with the circuit...two transistors (three when I add the power transistor for running the big LED), a 555 timer, half-dozen resistors and a batch of capacitors. We'll see.

Ron Wanttaja

[cluttonfred]

Ron, glad to see you are still slaving away to make this idea a reality. I wish I could be more help, but nonetheless BRAVO! I can't wait to dogfight your Fly Baby with a Yak-like Taylor Monoplane.

[Frank Giger]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.

[rwanttaja]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.

Yeah, but it's ****ing me off. :-)

I think it's due to capacitors charging. The audio input is a strong impulse, and most designs are slanted towards music. The big whomping voltage hits, and doesn't get passed until the capacitor's charged. No question it started working better when I reduced the RC time constant for the 555.

But I'm having a good time. Don't think I've built a transistor amplifier for nearly 30 years; worked some IC stuff slightly more recently. Been having some construction issues...worked fine in breadboard, but DIDN'T work when soldered onto a board (yes, I heat-sink the transistors). Gotta work that one out. I used to hand-solder ICs to circuit boards without sockets, and I'm hoping the hands have not lost what cunning they used to possess.

Ron Wanttaja

[rwanttaja]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.

Looks like it was just an audio power issue. I was testing the single-shot mode using an old cassette-type walkman, and the machine-gun mode from the audio of my smartphone. I have a speaker to monitor the gun sound, and it was obviously must quieter on the smart phone. So I made a tape of the machine-gun sound, and things seemed to work right. Here's a brief video showing the result:

http://www.bowersflybaby.com/gunvideo2.wmv

Note that the rhythm of the gun is a bit uneven (I just strung together duplicates of one Mosin-Nagant shot) but the high-powered LED is tracking it pretty well.

I want to fiddle with the circuit a bit, but otherwise, I'll be posting a schematic in a couple of days.

Ron Wanttaja

[cluttonfred]

Great stuff, Ron! Just counting by ear and watching the time on the video clip, it seems to me that you are getting a "rate of fire" of about 200 RPM. Any thoughts on how you might get that a little higher, and how to get the sound loud enough to be heard over an engine and prop?

Looks like it was just an audio power issue. I was testing the single-shot mode using an old cassette-type walkman, and the machine-gun mode from the audio of my smartphone. I have a speaker to monitor the gun sound, and it was obviously must quieter on the smart phone. So I made a tape of the machine-gun sound, and things seemed to work right. Here's a brief video showing the result:

http://www.bowersflybaby.com/gunvideo2.wmv

Note that the rhythm of the gun is a bit uneven (I just strung together duplicates of one Mosin-Nagant shot) but the high-powered LED is tracking it pretty well.

I want to fiddle with the circuit a bit, but otherwise, I'll be posting a schematic in a couple of days.

Ron Wanttaja

[rwanttaja]

Great stuff, Ron! Just counting by ear and watching the time on the video clip, it seems to me that you are getting a "rate of fire" of about 200 RPM. Any thoughts on how you might get that a little higher, and how to get the sound loud enough to be heard over an engine and prop?

Rate of fire isn't an issue. Rate is set by the audio file, and the one I'm using was built by stacking single shots atop each other. Just have to pack them tighter. I'll have to try a higher rate, though, to be sure the flashes just don't blend into a constant beam. Might need a slight change in resistors.

Making it loud enough? Don't have any idea, other than a big amp and a ruggedized speaker. That is going to be difficult, and is going to take some heavy-duty power.

Ron Wanttaja

[rwanttaja]

Rate of fire isn't an issue. Rate is set by the audio file, and the one I'm using was built by stacking single shots atop each other. Just have to pack them tighter. I'll have to try a higher rate, though, to be sure the flashes just don't blend into a constant beam. Might need a slight change in resistors.

OK, dropped a resistor a bit and eliminated some attenuation on the input, and it worked at about a ~400 RPM rate. One issue is that the flash becomes basically, the LED on constantly with a bit of a flicker. If you're going with that high a rate, I'd just use a simple flasher circuit and not bother to have the synchronization. I like the way it syncs to the slower fire rate in the video...if you watch "The Blue Max" again, you'll hear fairly low firing rates for the machine guns. The guns might be spec'ed at 500 RPM, but you put an interruptor gear in there.... Not applicable to Frank's Lewis, of course.

In any case, the schematic is attached. Everything but the high-power LED can be bought at Radio Shack. The resistor and capacitor on the input is what I used on my ~200 RPM audio file. Wire the audio input directly to the base of the first transistor if you use a high firing rate.

And I'm not done. I want to try some improvements to the "Flash only" circuit I put together a month or so back. It struck me that I might be able to gimmick the output to produce a series of pulses that might not sound too bad after being run through an amplifier. Less complex, easier to build...and the quality issues will be less important at 500 RPM. We'll see.....

Ron Wanttaja

[cluttonfred]

You are my hero, Ron. Red Baron, look out, here comes Snoopy!

[rwanttaja]

OK, the simple flasher-only circuit was...err, simple. One IC, one transistor, three resistors, two capacitors. With the addition of a third capacitor, it does provide an audio output that could be amplified.

http://www.bowersflybaby.com/gunvideo3.wmv

This example has a small speaker attached... does give a "Takatakataka" sound. Shove it through a mondo amplifier, out a rugged bullhorn-type speaker, and distorted by the slipstream, it'll probably sound close enough.

I'm going to solder up a PC-board version for Frank, I'll post a schematic and pictures when done.

Ron Wanttaja