Pyrotechnic firing sequencer

[dodgey]

Hi all, I want to build a sequencer (much like the led sequencer circuits you find everywhere) which instead of lighting LEDs sends approx 12v to an electronic match (think of it as a 12v lamp - (which takes a lot more current to light than an e-match takes to fire!)).

I'd like up to 16ish channels, but less will do. I'd like to be able to control the speed of the sequence from start to finish (no repeat is nescessary!). A simply POT adjustment would do.

Finally, I'd like to trigger the sequence with a 12v pulse (push of a firing button from my main 12v firing system)

I've found this page...

**broken link removed**

and am looking at knocking up the 16 led sequencer with the added transistors for 12v support and then somehow knobbling the return sequence (shouldn't be har I guess).

I'm fairly good with BASIC electronics (I built my own firing system, and am fine with diodes, resistors etc and have used transistors and ICs but don't understand properly how they work).

Are there any example circuit diags out there I can look at?

p.s. I really want to make this as the comercial products start at about £800!!! as soon as you associate anything with professional pyro the price goes up by x10!

 

[dodgey]

Or... how about (on the 10 channel sequencer below) I replace the 3904 transistors with higher current alternatives and lower to 120ohm resistor value?

**broken link removed**

 

[Nigel Goodwin]

As I see it, there are two parts to this - the first is the sequencing logic, personally (in the 21st century) I'd use a PIC to do it, you could easily adjust the individual delays to give any sequence you wanted. This would make the circuit VERY simple, at the cost of some simple software - 16 channels (or more) would be easy to do.

The second part is the actual driver for firing the ignitor, you would need one for each output channel, but it depends on the current and voltage they require, and also how 'destructively' they ignite - it's quite likely they may go short circuit, so the drivers would need to be designed to withstand that.

 

[dodgey]

Thanks Nigel.

In reverse order: they usually go short circuit after ignition.

Pic - I see, obviously way beyond me at the moment.

Actually, I've just bought a kit from Maplin that drives 8 x running board style LEDs so I'm going to have a dick around tonight with it ("amplify the drivers if necs. with extra transistors). I'll fish the ematch figures out tonight. I know they require very little to fire indeed.

Going back to the PIC element - can anyone recommend a good book for a beginner. Same with electonics really. I'm getting into this more and more. I used to be a programmer back in the days of Spectrums ! :-O which should help with the logic and Pics etc.

I'd love to be able to build a nice controllable sequencer and I've got a feeling I'll be able to learn enough in a while to do it.

 

[Dr.EM]

Is it not possible to use relays for this? It depends how fast your going, and you'd probably need a small transistor to drive the coil (or possibly a logic driver array would be suitable?). I'm sure a relays contacts used with a suitable power supply would'nt get damaged from being shorted :?:

 

[bmcculla]

I'd use a capacitor for each channel to store energy. The caps would trickle charge up to 12V (just a simple series resistor). You then use a FET to dump the energy in the cap through the igniter. Once the energy in the cap is expended even if the FET stays on you only have the trickle charge current going through the short. The other advantage to this method is you can deliver high power pulses with a small battery.

 

[spuffock]

Take a look at www.microchip.com. Download MPLAB. It's free.
Have a play with the simulator. Like it? Now buy an ICD2.
The PIC16F877 is nice to play with.........
Sorry I got you hooked. There isn't a cure. :shock:

 

[dodgey]

hehe. Got a desk covered in wires at the moment. Used a simple Maplins led chaser running a 555 timer and a 4015 shift register(I sound confident but have little knowledge how they work!- i have read up a bit - high/low state etc). The LEDs are supported with 3k resistors. I bypassed the resistor on one channel and got about 10volts accross it when the LED should have lit.

Great I thought, so I whacked an ignitor accross instead. Nothing :-( and the sequence stops until I reset it (lack of resistance back to the IC I guess). So then I tried amplifying the signal, but soon realised I need to learn a lot (like I need an NPN as well as a PNP transistor).

The sims sound cool. will take a look. Currenty using Croc clips and livewire.

One thing that would help me no end... On this link, under "Interfacing 5 volt CMOS to 12 volt/ 25 Watt Loads" - what does the "51" mean - looks like a resistor to me. 51ohm resistor?. Trying to steal the amplifier and apply it to my circuit.

**broken link removed**

One more thing, on the same page, under the heading "16 Stage Bi-Directional LED Sequencer" - what are the trianges? diodes? and why is one part of the circuit floating unconnected? Sorry if I sound like a dullard, but I'm used to circuits, that, well, form circuits!

The idea (bmculla) with the Caps and FETS sounds very good. Would give the clout to run fast sequences I guess. Way beyond my current abilities

Looks like I need to trawl through my phone book and find an old pal with an oscilloscope

Will keep trying!

 

[Dialtone]

1. Your assumption is correct. In the schematic, the 51 is the resistance; 51 ohms. Although not too common, not as hard to find as you may think either.
2. The triangle symbol (with the circle) is an inverting amplifier, in this case a Schmitt Trigger. Think of it as a device that takes a not so clean input and inverts and shapes the output to a more square shape. In the schematics, they are using several Schmitts along with resistors and caps to form osc to derive the basic clocks/ timing signals. These outputs then feed a second Schmitt element that is used to reshape/invert the inputs to something more acceptable to the IC's.
3. The floating section you referred to is simply the leftover schmitt elements inside the 74xx14 dip package. Each dip package has 6 elements inside and these are unused in this case. Also, it is shown on the schematic as a reminder that the package requires a voltage supply and ground on pins 7 & 14 even if all elements are not used. Also, if you will notice, the unused elements inputs are tied to ground. This keeps them from trying to osc on their own and generating extra noise in the dc input supply.
Hope this helps.
Dialtone

 

[dodgey]

Dialtone - thanks a million. All makes perfect sense now.

 

[dodgey]

One more thing (there always it). - I'm guessing I ought to get my head around basic electronics a bit more before I got delving into PIC programming? Otherwise I won't have the understanding to build output and input circuits for the PICS? or is there a shortcut?

 

[Nigel Goodwin]

One more thing (there always it). - I'm guessing I ought to get my head around basic electronics a bit more before I got delving into PIC programming? Otherwise I won't have the understanding to build output and input circuits for the PICS? or is there a shortcut?

Using PIC's greatly simplifies the electronics in a project, but you still require input and output circuitry (usually!). You might try my tutorials?, in particular check the 'Hardware Extras' section for some simple interfacing examples.

 

[dodgey]

OMG! nice one. That's my Weekend reading sorted :---)

The worst bit is my office is right above Maplins

 

[dodgey]

Oh dear. Started reading. I can tell this is the end of my life as I know it! Looks very well explained and interesting :--------------)

 

[dodgey]

Got the ematch / ignitor specs: they require 0.5 amps to fire. resistance is 1.18 +/- 0.12 ohm

 

[Dialtone]

Now that we have you hooked fairly firmly, let me give you some line to run with and make your day more interesting.
Suppose you could sequence your fireworks display to music. Would that be a hoot? Check out this site

**broken link removed**

In this link is a design for a scaleable ( and very simple) PC based controller that uses a single chip for each 8 bits of control (74HCT595) . This chip is a serial in/ parallel out somewhat similar to the link you posted. (section 4 has the schematic links but is hard to spot)

Now check out this link
**broken link removed**
This link gets you some really cool free software (Comet) that is able to run the controller in the previous link and sequence the operations to music.

Although the above sites are primarily dedicated to computer control of Christmas lighting, the basic ideas can be adapted to almost any use, and would be a perfect compliment to your fireworks sequencer.

Since the above runs off a PC parallel port, you can tinker around with your basic control design without learning PIC, refine things, then if you want to, incorporate the PIC aspects later.

Have fun
Dialtone

 

[dodgey]

Dialtone - nice link endless possibilities

Nigel - just ordered all the components to run your training course. - looks fairly easy to grasp. Lots to learn (fitting it in with motorbikes, fireworks, and model helicopters!)

Skipped the 40 pin PIc for the time being as the 20 quid programmer I ordered doesn't support it. Lets see how I get on

Now I'm doomed!

p.s. jumping the gun a bit but darlingtons look like they may be useful...

 

[spuffock]

Now look at N Channel power mosfets..... :twisted:

 

[dodgey]

Guys, I need your help. I'm learning PIC and getting on well. I have the hex I need, and a circuit diag. I'm trying to find PCB software to help me make the board (print it with a laser printer etc). Problem is this. I have croc clips. No good. Only basic ICs. I don't need to emulate, merely built the circuit to import into a pcb designer with routing.

I've tried circuit maker with trax maker, made a custom (macro) chip with 40 pins but fail to import into traxmaker. Keeps going on about missing patterns from the netlist. Tried adding to the netlist with no luck/understanding. Is there a s/w package out there that recognises PIC chips and will let me design and import to a PCB designer?

The moment I get a 40 Pin DIP into a pcb wizard I'm away. Just can't fathom how to do that bit :-(

Like I said. Don't need to simulate, though that would be unbeleivably good if I could (i.e. sim pic hex and physical electronics)

To calirify, I'm thinking, "wouldnt it be great if i could desicgn a circuit, forgetting testing, import into a pcb designer that optimises the layout, for one layer, and maybe says, hey, I can't do this, you need a few links on the top of the board, here they are....."

 

[Someone Electro]

shodent be to complicated since PICs don't need los of external componets

you only need an crystal or resonator (you can run an PIC on its internal oscilator too)a clean power suply and some MOSFETs or power transistors


watch that you wont have big voltage slumps wen the ignitors start fiering(500mA each is quite some curent).Noisy power surce causes a PIC to reset or freze

edit:
almost forgot.
if youre going to run it off baterys run it of litium baterys.They can provide high curents and have an very stable voltage. NiCd ones wod work too.

I got two litum batery out of some broken cell phones