233 replies to this topic

[pyrotechnist]

i'me sorry but flashy could you by anychance make that example circuit you showed me into an example firing system with the voltage supply their and everything you need for it? Thanks.

Edited by pyrotechnist, 01 February 2005 - 08:32 PM.

[Flashy]

i'me sorry but flashy could you by anychance make that example circuit you showed me into an example firing system with the voltage supply their and everything you need for it? Thanks.

Hi there pyrotechnist,

I don't have time right now to make you up a diagram but i will be able to do it at the weekend. What application did you use to make that diagram? It looks like Crocodile clips or maybe electronics workbench. If you could let me know what program your using it'll make things easier for me, even better would be if you have a copy of the file on disk that you could send me by email.

[pyrotechnist]

Hi there pyrotechnist,

I don't have time right now to make you up a diagram but i will be able to do it at the weekend. What application did you use to make that diagram? It looks like Crocodile clips or maybe electronics workbench. If you could let me know what program your using it'll make things easier for me, even better would be if you have a copy of the file on disk that you could send me by email.

I am using a trial version of croc clips. Thanks for the help . I only have images due to it won't let you save on the trial version .

[Frankie]

Hi all,
I've just joined the forum - a forum virgin you could say. Anyway me and a mate have been 'Portfire' lighting pyro now for about 8 years but last November had a go with a totally electric system - brillient. Now we've got the bug and want to get hold of a kit but looking on the web it appears very expensive so thought we would have a go at constructing our own. Ive got a pretty good workshop and I trained as an electrician, some years ago, so think we should be able handle the technical side. So what I'm after is some help with circuit diagrams and specs (required voltages etc) can anyone point me in the right direction?

[ProfHawking]

The spec will probably all depend on what electirc matches you are using. All electric matches are current dependant, ie will blow at 500mA or whatever, if at 1v or 100v.
Most commercial ones will have a particular current required to set them off, and a smaller current up to which they will not go off, to enable checking of connection.
I think aprox guides are up to 50mA for checking connection, and allow up to 600mA to get a garrenteed fire.
If you use your own matches you will have to test them yourself using current logging equipment. Try and make them all as similar as possible to prevent missfires or accidental fires.

The one thing that must not happen is that your connection checking current is enough to set it off, or that you have the posibility of a connection problem or short that could trigger a match.
All i can say is test test test, before attaching any actual fireworks to the kit.

As for your system;
There are fancy capacative discharge systems, but i doubt you will need anything that complex. That leaves 2 types of standard systems as far as im aware, the simple one wire is one match, or the IC based systems with a microprocessor based head that lets you have less wires and control more devices. Each to their own, one for simplicity one for features. It depends how confident you are with your electronics.

The wiring you use is important - long lengths of thin cable have a surprisingly high resistance, especially if carrying a reasonable current. I'm trying to make a system that uses cat5, but im coming up with troubles with this effect. If you build in allowance for the resistance, then using short runs could be dangerous. If you can afford a long length of multicore high current cable then that would be best.
Make sure your cables & connections are protected against mosture. The amount of dew the devices seem to attach themseleves in is suprising even by early evening on a winters day.

An inevatable word about safety - make sure your system is "fail safe" so if some disaster happens nothing goes off, rather than "fail unsafe" when all hell breaks loose.
Give your system a key switch - but it is essential to have the key remoable in only the off position, otherwise you could accidentally leave it on without realising.
The last system i made had a buzzer built into it, as well as the standard light, to give you extra warning whenever it was turned on.

Good luck!

[Frankie]

The spec will probably all depend on what electirc matches you are using. All electric matches are current dependant, ie will blow at 500mA or whatever, if at 1v or 100v.
Most commercial ones will have a particular current required to set them off, and a smaller current up to which they will not go off, to enable checking of connection.
I think aprox guides are up to 50mA for checking connection, and allow up to 600mA to get a garrenteed fire.
If you use your own matches you will have to test them yourself using current logging equipment. Try and make them all as similar as possible to prevent missfires or accidental fires.

The one thing that must not happen is that your connection checking current is enough to set it off, or that you have the posibility of a connection problem or short that could trigger a match.
All i can say is test test test, before attaching any actual fireworks to the kit.

As for your system;
There are fancy capacative discharge systems, but i doubt you will need anything that complex. That leaves 2 types of standard systems as far as im aware,  the simple one wire is one match, or the IC based systems with a microprocessor based head that lets you have less wires and control more devices. Each to their own, one for simplicity one for features. It depends how confident you are with your electronics.

The wiring you use is important - long lengths of thin cable have a surprisingly high resistance, especially if carrying a reasonable current. I'm trying to make a system that uses cat5, but im coming up with troubles with this effect. If you build in allowance for the resistance, then using short runs could be dangerous. If you can afford a long length of multicore high current cable then that would be best.
Make sure your cables & connections are protected against mosture. The amount of dew the devices seem to attach themseleves in is suprising even by early evening on a winters day.

An inevatable word about safety - make sure your system is "fail safe" so if some disaster happens nothing goes off, rather than "fail unsafe" when all hell breaks loose.
Give your system a key switch - but it is essential to have the key remoable in only the off position, otherwise you could accidentally leave it on without realising.
The last system i made had a buzzer built into it, as well as the standard light, to give you extra warning whenever it was turned on.

Good luck!

Many thanks for the information, it's just what I need, now to the drawing board to try and design the circuit diagram. I'll post my efforts for comment. Thanks again.

[pyrotechnist]

Dam i am totaly lost, i am trying to modify my testing circuit so it is more electronic. I am wondering if you can make a circuit take an if conditional statment using electrical componants? so like if input 1 == 0 output = 2 else output = 1. I even tried integrating a PIC chip but it didn't like diod's, i got that working thuo fine and it swaped from one bulb(representing a firework) on and waited for so long then turned it off, then i put a time on for when i whanted it to go to the next cue ect. But i don't know if i could make that more electronic. Is their anyone her ho can show an example with a PIC chip in it? thanks.

[ProfHawking]

You can use PICs but to be honest thats probably more hassle than its worth. if you want an IC controlled circuit, have a look at using BCD decoders instead. they should replace the PIC and are cheap as chips ( 32p from RS - 640-456 )
Can your free version of crocodile clips open existing files? if so have a look at http://highspeed1.cl....uk/firesys.cyt - might give you some ideas.
The components can all be had from RS. use a BCD encoder rotary switch to select channel 0-9 RS part: 333-063 (there isnt one of them in croc clips do you have to do it yourself with the buttons) The selection display is an optional extra.
Be careful if you try this circuit with the capacitor on the end of the wire. this is to compensate for the resistance in the long length of wire. You probably will want to put a large-ish value resistor across it so that it discarges to a safe level when the power is cut within a few secs.

[adamw]

Dam i am totaly lost, i am trying to modify my testing circuit so it is more electronic. I am wondering if you can make a circuit take an if conditional statment using electrical componants? so like if input 1 == 0 output = 2 else output = 1

Why not use a combination of AND, XOR gates etc.

[alany]

In that particular case all you need is a inverter (NOT) gate.

For more complex boolean logic you'll find Karnaugh Maps useful.

[pyrotechnist]

Hi thanks for the info, i can't open that circuit internet explorer won't download it. So i don't know what rong with that. Well i have had to do another circuit because my time is running out, so i made a circuit now that is very basic but uses lots of timers to accomplish different timed out cues. Thanks for the help.

[adamw]

Just a NOT gate? Oh heh. It's a long time since I did gates.

[Andrew]

One problem with using a single NOT gate is that there is an 83% redundancy in the chip. On an economic/environmental sence this is bad. If everything was that redundant we would have already run out of lead and dopeing elements. Not having a moan, but engineering is about finding a solution that works, is efficient, and costs as little as posible (cost in money, time, materials and the impact on the environment). You might think that one chip isn't really going to make a difference, but to make that one chip has produced at least a hundred times (closer to a thousand times)i t's weight in waste and polution. We all know that turning off redundant lights saves collectively, a lot of energy, the same applies to waste and polution.

A less redundant solution to a line tester design, that is also more electronic and safer than a single chip, is by using a small MOS or HEX FET, a couple resistors and an LED if you wish. It could be made to run from any power source (within reason) with minimal componants. if size is your issue, this could be made smaller than a small finger nail, and powered from a battery the size of a pea!

I will post a circuit diagram and calculations when I work out how to do it.

[Andrew]

What is even better, is that a line tester that uses nanoamps to test and is smaller than a little finger nail would cost less than 20p + a 16p battery.

Nanoamps is small enough to test even the most sensitive ignitors in the world with no chance of accidental ignition.

[alany]

If I was going to use only a single inverter I'd just use a generic transistor, probably an NPN because they are so cheap and ubitiquous, but if you prefer FETs could be used. I think you overestimate just how much actual semiconductor is in a 74 or 4000 series chip, we won't be running out of elements any time soon. The big issue is the insane amounts of energy it takes to produce such low entropy materials, fighting the 2nd law of thermdynamics takes lots of work.

The problem with using vanishingly small testing loop currents is that the insulation leakage of long damp shooting lines can become a problem. A few mA is quite acceptable and unlikely to be spoofed by RFI or leakage. A LED and resistor will work just fine for that. It is the best engineering solution, cheap, simple and robust.