Activating Electric Valve (& selecting said valve)

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,505
I’m researching a theatrical special effect that is essentially a confetti cannon on your wrist.

So the givens. I’d like to mount a CO2 cartridge on a wrist board. It would connect to a valve which would evacuate a cylinder packed with confetti.

There are projects on the web which do this. But they use a plumbing bulky lever valve to open the gas into the load cylinder.

So I’m investigating an electrical valve. The parameters are that it must be rated for 900 psi AND be operated by low voltage (I’ve seen 12V valves) I’m sure this would be less bulky than s plumbing cut off valve AND be easier for the actress to activate.

But what I haven’t seen are current requirements. I was thinking of running it of a USB battery pack. But, will a boost circuit up to 12V have enough current to operate the valve?

Please help!
Thanks,
Don
 

Sensacell

Joined Jun 19, 2012
2,568
900 PSI makes for slim chances of finding any small low-power valves.

A mechanical solution to pierce the CO2 cylinder on demand, as they do for life vests might we the way to go.
 

jpanhalt

Joined Jan 18, 2008
9,710
Have you considered copying or re-purposing an electronic paintball gun?

Lots of stuff about that popular "sport." Here's one link: https://www.thoughtco.com/electronic-versus-mechanical-guns-2565831
I really have no interest in paintballs, but it seems portability and light weight should be important to those makers too.

Edit: "Low cost" new prices appear to be $200 to $300. Craigslist in Cleveland had this for $50: https://cleveland.craigslist.org/spo/d/cleveland-paintball-spyder-mr2/6827410650.html
 
Last edited:

Yaakov

Joined Jan 27, 2019
1,612
It makes me wince to think of the outcome of a valve failing open with a full CO₂ valve on the high side.

Perhaps a cylinder of air, filled with a bicycle pump, even secreted in the costume remotely from the working end?

It also offers more choice in valves by reducing the pressure at the control end.
 

jpanhalt

Joined Jan 18, 2008
9,710
One can get CO2 cylinders of various sizes, including some pretty small ones that are refillable. They are used in very lightweight model airplanes. Just be sure the cylinder is insulated from flesh, as they get pretty cold. Of course, an air cylinder will too.
 

Yaakov

Joined Jan 27, 2019
1,612
One can get CO2 cylinders of various sizes, including some pretty small ones that are refillable. They are used in very lightweight model airplanes. Just be sure the cylinder is insulated from flesh, as they get pretty cold. Of course, an air cylinder will too.
CO₂ cylinders have the advantage of high pressure which I perceive as a disadvantage in this case. I also don't imagine this will be a "repeater", rather a single shot, and so CO₂ seems overkill.
 

jpanhalt

Joined Jan 18, 2008
9,710
CO2 is simply an example of an easily liquidfiable, non-combustible gas. There is lots of experience with it being used safely. In fact, the manlift I use specifies CO2 and not air or nitrogen.

Lots of other gases liguidfy at room temperature and lower pressures, like R-134a. I think djsfantasi's main interest was an electronic valve.
 

Yaakov

Joined Jan 27, 2019
1,612
Yes but in disposable cartridges the pressure is very high and the project doesn’t seem to need it, and, were it to discharge unchecked from the body worn projector, it could be a real hazard.

I would prototype the canon then test it’s performance with fair air pressures from a tank to determine if air is practical as I expect it is, then choose the valve, etc.
 

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,505
900 PSI makes for slim chances of finding any small low-power valves.

A mechanical solution to pierce the CO2 cylinder on demand, as they do for life vests might we the way to go.
An excellent point! But the constraints of having this hidden within the actors costume and the requirement that the audience NOT detect any triggering action, make make this difficult.

I’ve found a 12V 1/4” 900 psi valve. But no.
 

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,505
Have you considered copying or re-purposing an electronic paintball gun?

Lots of stuff about that popular "sport." Here's one link: https://www.thoughtco.com/electronic-versus-mechanical-guns-2565831
I really have no interest in paintballs, but it seems portability and light weight should be important to those makers too.

Edit: "Low cost" new prices appear to be $200 to $300. Craigslist in Cleveland had this for $50: https://cleveland.craigslist.org/spo/d/cleveland-paintball-spyder-mr2/6827410650.html
Interesting! The CO2 adapter is a repair part from a paintball gun. Never thought of re-purposing an entire gun. However those prices may be a no go.
 

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,505
First, this device will be used in a stage production of “Frozen: The Musical” when Elsa uses her powers, the confetti / ice & snow shoots from her hand.

A soft foam board will attach to the actress’s arm with Velcro straps. The entire assembly consists of a CO2 adapter connected to a cut-off valve connected to a cylinder. All connections are brass threaded fittings.

Yes but in disposable cartridges the pressure is very high and the project doesn’t seem to need it, and, were it to discharge unchecked from the body worn projector, it could be a real hazard.

I would prototype the canon then test it’s performance with fair air pressures from a tank to determine if air is practical as I expect it is, then choose the valve, etc.
The high pressure of a CO2 cartridge is a design requirement. They are used in commercial wrist cannons. They need to shoot a small cylinder of confetti 20’ across the stage. Note, the confetti is what’s shot; not the cylinder!

Maybe that’s why this DIY design used a large plumbing cut-off valve. Doesn’t fail open.
 

Yaakov

Joined Jan 27, 2019
1,612
I understood the intention of the device. My concern is the idea it would discharge the entire content of the cylinder, not the cylinder itself!

That’s a lot of cryogenic gas near a person, and a lot of pressure potentially in the direction of others.

I am confident that you will take safety precautions, but it still makes me nervous.

They don’t list Frozen, but maybe a quick call to these folks could be productive: http://www.theatrefx.com/show-specific-effects.html

They have confetti canons as one of their products.
 

Thread Starter

djsfantasi

Joined Apr 11, 2010
6,505
I understood the intention of the device. My concern is the idea it would discharge the entire content of the cylinder, not the cylinder itself!

That’s a lot of cryogenic gas near a person, and a lot of pressure potentially in the direction of others.

I am confident that you will take safety precautions, but it still makes me nervous.

They don’t list Frozen, but maybe a quick call to these folks could be productive: http://www.theatrefx.com/show-specific-effects.html

They have confetti canons as one of their products.
Your concerns made me think of an increased safety design. Place the electric valve in series with the cut-off valve. That way,
  • the device can be armed just before it’s needed
  • arming the device can be done in advance of the arm action, thus not being as obvious during the actual discharge
  • buying or renting a commercial unit would cut into my side business profits of creating theatrical special effects
 
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