Fireworks/pyrotechnics Sequencer

[Pete Firth]

Hello all, Sorry I'm a bit of a neewb (this is my first post), I have a fair understanding of electronics and circuits but when it comes to resistors capacitors micro controllers etc I'm totally out of my depth!

I'm trying to work out the circuit for what I believe (maybe showing my ignorance!?) should be a fairly straightforward project. and I'm hoping that some of you may be able to help with the circuit design/planning.

The Dream: a simple sequencer that is triggered from an electrical pulse (sent from an existing firing system) triggers a sequencer, i.e. an electric pulse incoming, and on each subsequent input pulse advances to the next output, each output is a pulse of current that goes to an 'electric match' basically a resistor that gets overpowered and burns up igniting a firework fuse or lift charge.
So similar to an led counter circuit where each press of a button lights a different LED, just in this case theres an led and a current sent to the ignitor to fire the firework connected.

The system will be powered by 2 x 9v batteries (18v), there should be a continuity test function with an LED to indicate a complete circuit, and an LED indicator for each output pulse (can use the same LED), the counter should also reset to 0 on power cycle, in theory a simple CD4017 decade counter should do the trick as I only want 6 or 10 queues / channels on this system, the continuity test will need to be at less than 15mA, the ignitors are not sensitive to current direction, and once fired the circuit is broken, however some sort of dead short protection is probably a good idea.

So, its a stand alone system with its own 18v power supply, when switched on it should show/indicate if there is continuity on each of the output circuits, the trigger is a pulse of current from a separate system, each time an input pulse is detected it should send current to an ignitor in sequence [pulse #1 (p1) fires queue 1(q1), p2 fires q2, p3 fires q3 and so on..].

Its worth noting that it should not include any mechanical relays etc, as in a failure this could cause a dangerous occurrence! these sort of systems often employ fets (but I'm not entirely sure I understand what they do..

I hope thats enough information to get started? I think I can get my head around circuitry that would make this work but I'm clueless as to what resistors capacitors etc I would need to protect the circuit and make it function reliably.

Any help would be much appreciated!

 

[Pete Firth]

I should add that there are a few similar ideas floating about on this forum, but none that quite get me there, however the discussion linked below does answer a few questions:

Electronic firing system - for fireworks

Hi guys, Firstly let me say that I have my licence for fireworks, so this is all above board. I am trying to avoid paying for a professional firing system, as they are really expensive. I don't have the too much experience in building circuits, and I thought it would be a lot easier than...

www.electro-tech-online.com

the circuit they came up with in the end is linked below, it would need modifying to cope with 18v, and rather than a push switch to fire a single queue an input current and maybe a decade counter to automatically advance to the next queue in the sequence:

https://www.electro-tech-online.com/attachments/fire-control-mod-3-gif.22722/

obviously no need to reinvent the wheel.. but if someone has the knowledge and is willing to help with combining the two ideas into a circuit that might work it would be much appreciated!

 

[danadak]

Question already present, so deleted the question in this post.

 

[danadak]

One possibility, single chip. Right hand window shows many more onchip
resources available. 16 channels shown, I think 32 would rout..... A simple OLED
could be added for user interface....

Here is what is onchip, many have multiple copies :

IDE (PSOC Creator) and IDE free, board dependent on # channels (eg. I/O needed) but the $15
CY8CKIT-059 board good starting point.

Would be able to incorporate a timing facility that inserts inter shot waits / delays dependent on what is being shot.

 

[rjenkinsgb]

What is the worst-case current through an igniter, and maximum current pulse time?

 

[Pete Firth]

Thanks both for your responses!

danadak, although that may be a little overwhelming, I need a maximum of 10 channels per unit (the plan would be to make 4 of these ideally) and no need for any timing facility or variable delays between queues, the timing should come from the input pulse. this would mean that from 1 queue on my existing firing system I can fire 10 queues via this circuit by re 'firing' or activating the queue.

rjenkinsgb, the standard current pulse time is 1/10th of a second but worst case would be 2 seconds, and 18v 2A would be more than enough current to fire pretty much any igniter (a 9v battery touching the wires would fire most queues without issue)... generally you want a minimum of 12v 1A at the ignitor/match

 

[schmitt trigger]

I would use auto-protected Mosfets.
I have used the Omnifet II series from STMicro, they are extremely rugged.
OnSemi also has a similar Smart Switch series.

Those have over current, temperature and voltage protection, plus the gate is fully clamped.

 

[Pete Firth]

hello all, heres my attempt to draw the circuit I had come up with, I understand I will need further components to protect the system and effect an auto reset and note that I have no idea about the actual components needed and their values. any help to flesh this out into a workable idea gratefully received.

 

[danadak]

This would use Arduino. Use block language to program. This would be a
basic design.

Note post #4 may look complicated but its drag and drop, and includes the SAR
to be able to verify connections to match(s) is good. Each resource has API's
written to manipulate it, so programing pretty simple. And whole design is 1 chip.

The design at top is simpler, Arduino boards pretty cheap and simple to work with.
6'th graders are using it to program direction finding robots in schools. The program
used is mBlock and Arduino, both free.

As an aside I use block programing for many projects being a visual learner. For
projects that have more stringent HW issue I use C. C is a "strongly typed" language,
and has a significant learning curve. Gives users more control at the expense of
un yielding rigid typing.

Regards, Dana.