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BBMG triggered by monostable 555

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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BBMG triggered by monostable 555

Unread postAuthor: evilvet » Wed Apr 06, 2011 7:32 am

Posit:
    A BBMG is inherently wasteful
    Regulated triggering may be a solution
    Remove the waste by using a timed trigger

Solution:
    A 555 timer used as a trigger for a solenoid


This is my plan, red wine is currently interfering with production this evening but comments welcome.

I propose this circuit to trigger the solenoid, in place of R1 I use a 100kOhm pot to allow for variable time. T= 1.1 x R x C where C is fixed.

Technician, JSR, your thoughts ?
(Edit: Not forgetting PVC Arsenal and Ramses who answered my earlier thread on this subject)
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Unread postAuthor: POLAND_SPUD » Wed Apr 06, 2011 8:48 am

Edit: Not forgetting PVC Arsenal and Ramses who answered my earlier thread on this subject
ohh yeah and don't forget about POLAND_SPUD...

...this guy would probably tell you that you could have used a 3 way solenoid valve and a switch
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 06, 2011 9:13 am

A BBMG is inherently wasteful - agreed

Regulated triggering may be a solution - not quite. The source of a BBMG's inefficiency is the fact that you're feeding gas into a relatively huge chamber between the barrel and the valve, meaning you have a lot of pressure loss before the projectile is fired. Some tests I did with my vortex BBMG showed less than 20 psi in the BB chamber for a feed of 110 psi from the gas chamber

Pulsing the gas will save on gas, but not increase efficiency.

The only two solutions I think really contribute to efficiency are:

- o-ring detent, which rapidly seals off the chamber once the valve is opened, allowing air to accumulate until the round is fired - thus also increasing power - and also closing off the chamber when insufficient pressure is available.

- BBs stored directly in the air chamber vith a valve - this can be done either with a detent (a "valveless" type mechanism) or with say a ball valve between the barrel and chamber.
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Unread postAuthor: Technician1002 » Wed Apr 06, 2011 10:13 am

The only thing missing from the timer board is a proper driver to drive the gun. The timer is OK for lighting up a couple of LED's and other small indicators, but lacks the current output to directly drive a motor or solonoid.

Look into the "guns" the RC combat boat people use. They do fine with their RC controlled battleships.

http://www.rcnavalcombat.com/Forum/tabid/58/afv/topicsview/aff/535/Default.aspx

Driving an RC servo may be possible for cycling ammo feed and a valve.

http://www.rcnavalcombat.com/
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Unread postAuthor: evilvet » Wed Apr 06, 2011 2:58 pm

Technician1002 wrote:The only thing missing from the timer board is a proper driver to drive the gun.


Quite true, Bacchus made me post the wrong picture. The right one has a MOSFET on the output pin plus diodes to protect from the back flow from the coil.

Q:
Obviously the solenoid and valve itself have latency which I can find in the datasheet. Any idea what the latency is for a "standard" PCB 12v relay, how long does the coil take to energize and close the contacts? If I am dealing in split seconds I presume I have to factor that into the length of the timer pulse.

Thanks
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Unread postAuthor: evilvet » Wed Apr 06, 2011 3:01 pm

POLAND_SPUD wrote:
Edit: Not forgetting PVC Arsenal and Ramses who answered my earlier thread on this subject
ohh yeah and don't forget about POLAND_SPUD...

...this guy would probably tell you that you could have used a 3 way solenoid valve and a switch


:oops:
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Unread postAuthor: JDP12 » Wed Apr 06, 2011 3:06 pm

just a friendly side not.. youre new so I wont harp on it too much, but don't double post.

And yea, sorry. It would be a cool project, but even if you pulse it, you will still probably waste the same amount of air. you would need a detent of some sort.
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