Pyrotechnic Sequencer
#1
Posted 05 July 2011 - 04:56 PM
#2
Posted 05 July 2011 - 05:59 PM
#3
Posted 05 July 2011 - 07:16 PM
I'm trying to design this as a general timer for pyro. In this instance we will be using a push-button that I will have in the palm of my hand that will go into one of the DIO pins on the board (probably carried in a belt-pouch). This will have an event attached to it in code that will trigger each squib/maroon in succession, with pre-programmed delays.First off, I don't understand WHAT is, or WHO is (or even in WHICH way) the circuit will be actually triggered. Is it a switch within the gun?
Here's the set-up we used to test the blood pack with today. It's a push button with a 9V battery. This is a prety common setup for doing single shots in film and theatre, as it can be hidden up the actor's sleeve.
Pushing the button connects the squib/maroon across the battery. A cool thing was using a detachable battery connector, so I could hold my hand over the battery pins while we were setting up to make sure the circuit could never bee made until we were ready to go hot. Safety first
In future though, It may be useful to have either something on a gun to trigger it, or even some sort of audio/visual count-down timer that we can use to sync up everything. This would depend entirely on the scene being shot.
The problem wasn't the circuit, but the precision of timing with Netduino.
That's DEFINITELY interesting to know. I'm not sure what delay the squibs/maroons have themselves, and the variability in that.
I'm hoping to be able to experiment with that to determine if this is even the best option.
Last night I talked to a member on the forum chat, who is doing a similar system for launching rockets. He suggested that I should not expect any accuracy under 20ms, due to the variance in the igniter. (please correct me if I have miss-understood this).
The stunt we are planning is to have the entry/exit very close together, maybe 50ms, and then the wall hit around 100ms after that. We're not aiming for massive realism here as far as speed and timing, more to create the illusion that the shot has passed through and hit the wall.
As for the circuit, this is an initial sketch, and I'm interested in any feedback.
The MOSFETs that I am using for this were originally brought for a motor driver that I decided to replace with a single IC, as they were way over-spec for the motor I eventually ended up using.but you may connect the gate of the mosfet directly to the Netduino output
I tested a few different circuits, and found that the voltage required on the gate is too high to drive them right out of the Netduino DIO pins, which is why i've opted to use the first transistor (just a generic low power NPN type). I was not sure how well the smaller transistor would conduct, So I've opted to use R2 to lower the voltage there a bit. This may not be required.
In this particular application I wanted to be definitely sure that the base on the first transistor is pulled down to ground, because if that went high for whatever reason (and in experimentation we found that just static from someone touching the breadboard could do that without a pull-down), the charge would go off, which could result in anything between the annoyance of having to re-set everything or a ruined take, up to someone loosing a finger or even worseI'd simply avoid the transistor and all the resistors. Just connect the gate to any output.
If it would be a good idea to also pull the gate on the MOSFET down to ground, then I would definitely want to do this too.
Agreed there, I don't eitherI don't know the characteristics of a "maroon", but I think the R3 is totally useless
R3 is there because currently I don't know the resistance of the squibs (my multimeter is on loan to my brother). I added that in provisionally to limit the current, as I don't want to damage the MOSFET or anything else when the squib is triggered. Triggering should essentially create a short-circuit between the battery and ground for a few fractions of a second.
Once I'm able to measure the resistance through the squib and MOSFET, I'll re-evaluate this part of the circuit.
Thanks for your feedback, I'd rather someone tell me off for failing at electronics now, instead of setting light to my hair or something in front of a camera crew
#4
Posted 06 July 2011 - 04:21 AM
Attached Files
#5
Posted 06 July 2011 - 06:52 PM
#6
Posted 14 July 2011 - 06:12 AM
Attached Files
#7
Posted 14 July 2011 - 06:56 AM
It's simply great!...But is it anything serious? I mean, will we see anything on the big screen/TV?
I am happy that the circuit fit your target.
I know Yenka, but it's too restrictive as licensing, IMHO.
Here are a couple of free simulators, both very powerful (at least for hobbists):
From Texas Instruments here is Tina. In the truth it's a Hungarian company, named DesignSoft. This sim is *very* well done.
From Linear Technology here is LT Spice. Not at the level of Tina, but surely enough even for a circuit designer.
Cheers
#8
Posted 15 July 2011 - 01:22 PM
We are gradualy putting bits for the film up. All the indoors scenes will be filmed infront of an audience at a local theater, and we will ahve some demponstrations/workshops showing off things like editing and makeup effects.
Here's a rough edit of what we shot last weekend as a trailer,
http://www.youtube.com/watch?v=8s1CoDm9HDg
Unfortunately we did not shoot any pyrotechnics, as we were filming on public land.
You can follow the project on our website.
#9
Posted 15 July 2011 - 04:22 PM
I've always used Yenka (was previously called Crocodile Clips) that I still have a student licence for from school .. 10 years ago. If there's an open source sim that anyone would recommend I check out,that would be great.
Just for info, If you didnt know already, Yenka has a free license for Home users
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