patrickredmon

A few queries regarding components:
Would it be any different to use ZD0100 as the LED's (just to keep it a little cheaper)??
I can't find a SPDT 12V switch anywhere. I think I may swap the key switch with the toggle switch. That way you need to key in to test or fire. Can I use the jaycar part SM1030 (SPST)??

Do you agree I should use 2 lead acid batteries (12V)?

EDIT: Would OZS2604 from http://www.ozgear.com.au/electronicp...ays_Fuses2.htm work?? All the key switched seem to be 250VAC.

Or this: http://www.rsaustralia.com/cgi-bin/b...rodoid=1881276

eblc1388

No problem. The one I suggested is chosen for ease of mounting. To use ZD0100 LED, you also need to buy some cheap plastic clips(HP1100 from jaycar) to mount it.

You need the security of keyswitch in your application.

The RS one only rated at 125mA so is not suitable.

The OZS2501 or OZS2600 from OZgear.com fit the the purpose. The main consideration is current rating and not voltage rating at 12V usage.

One keyswitch allows key removal in either position while the other allows removal in one position only. The key is trapped in the other position. Personally I would choose this one.

There is no need for two 12V lead acid batteries. What is your reason to use two?

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L.Chung

patrickredmon

I thought that one wouldn't give the required current. I have only discussed it with the guy from the electronics store. Maybe he was trying to sell me extra. Do you think it is unnecessary.

What rating wire do I need?? I have been looking at ribbon type as it is the only stuff I can find with more than 10 cores. I will nee something like that so I can run out ignighters in groups of 10.

Also, I think I will use spring connectors like in "100-in-one" kits as my connectors. Jaycar don't sell them. Dick Smith do (www.dse.com.au). There is no issue using these is there???

Thanks again for your help!!

eblc1388

A single 12V GEL type battery would give out over 50 Amps for a short period of time and so one amp is of no consequence. You only need one 12V battery.

This is where I can't advise you much more as I know nothing about how these professional guys work and their code of practice. The answer depends largely on whether you are getting paid commerically for firing firework or you are just building one to fire them in your back garden.

For the former you have to look physically at how these guys wire up their ignitors and what knid of wires to be used. This is more commonly known as the "trick of the trade". There is some pyrotechnics forums that you can get help from too. Follow their practices and when you are good at it, you can then make changes to suit your own if necessary.

Ribbon cable may be too thin to pass good current for a long distance, expensive and difficult to join together, unless you are using them in a one off situation. Looks for multi-core cable in the cable stores.

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L.Chung

patrickredmon

CAT. NO. ZD0100
LED 3mm RED 15mcd

Emmitted colour: red
Lens colour: difused
Wave length: 700
nm: 90
Pd W: 45nW
If mA: 15
If mA (peak): 50
Min: 1.5
Vf (V) Typ: 2.0
Max: 2.8
IV Min: 3.0
MCD Typ: 5.0
Viewing Angle: 40

Are you sure this is OK?? It says peak current is 50mA.
Am I reading this incorrectly. Sorry for my ignorance!

eblc1388

You're reading the specification correctly. The LED will be damaged if more than 50mA is flowing in it.

But in the schematic, the current is only 11mA for typical LED with a 940 ohm resistor in series powered by 12V. So never could the current exceed a lot more than 11mA.

Don't worry. Tell you what, in the forum if one's calculation is slightly off, there will be a lot of other users offering help to correct it.

All make it better but ocasionally a not so smart guy(you *should* know by now who you are) will make it worse by offering pure bullshits.

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L.Chung

patrickredmon

http://www.semtronics.com.au/cat/1125.pdf

I have finally found a 3 position key switch. This will allow me to have "off" (with key removed), "test" and "armed". It is, however, only rated at 2 amps. It looks to me like the test circuit is not protected by the resistor, hence it could carry more than 2Amp. Is this correct?

Can I simply put the 10W resistor where S1 is, and remove S1 altogether. I would then add the 3 position switch where the 2 position switch is, with the middle position going nowhere.

This would be brilliant as this will only allow the key to be removed in the "OFF" position.

Can you recommend a board to put this all on??

eblc1388

It is not protected because the current can never exceed 15mA.

Yes, you can do that.

I would solder the resistors to the pin of LEDs and the LEDs to the push buttons directly so there is no need to use a separate circuit board to mount the resitors and this reduced the overall wirings. Of course you have to use insulation tubings(e.g. heat shrinkable) of some sorts to get good insulation. I have re-arranged the LED connections in the schematic so that its now easier to wire.

Attached Images

firewk3.png (5.0 KB, 201 views)

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L.Chung

patrickredmon

http://radum.com.au/shopping/product...roducts_id=233

This is the URL of a web site selling a 20M serial cable. I am interested in using it to run between my firing panel and the fireworks.

The company does not have any info on it, other than it is rated for 12V.

Do you think it will cope with 1Amp for short pulses?? How much damage could this do? I don't want to use it if it will burn out before the ignightors do!!!

eblc1388

The above cable is a 25-core data cable with very thin copper conductors. It may or may not melt with 1A current through it.

For back yard firework display, there is no harm to try using it. Otherwise use a proper multi-core cable instead. Look inside electrical stores for multi-core alarm cables or even CAT5 Lan cables.

__________________
L.Chung

Jason_TTU

Hello everybody, since I am new to this forum I will start by introducing my self. My name is Jason and I am a 20 year old EE major at Texas Tech University. I have been doing Pyro, lights and sound since my freshman year in highschool. I was the pyro guy and my high school hasn’t had pyro since I left. Every thing I know was self taught and learned by reading and experimentation.

Ok here’s my question: patrickredmon what kind of inghitors are you using? Nichrome wire or some kind of electric match or something?
Thanks-Jason

patrickredmon

I'm using FireDragon ignightors. Not 100% sure of the difference, but I think they are electric match. They are really the only ones available to me.

I thought that cable might be a little on the thin side. Can't find any 11+ core cable anywhere!! Will have to keep looking. Don't want to buy cable that burns out, and then lose the whole show!!

patrickredmon

I have modified the circuit slightly. What do you think?? Basically I have moved stuff a little so that it is a tiny bit cheaper. Fewer parts per circuit.
Is this likely to cause an issue??

Attached Images

firewk3_modified.png (11.7 KB, 137 views)

jrz126

Why the 2 470 ohm resistors? you could get away with using 1 1kohm for each. It's also bad practice to use 1 resistor for many LEDs like that. You want to have a resistor for each LED. This is due to the slight differences of the LEDs when they are manufactured, one LED might draw more current than the others, which would cause it to burn out (or drastically shorten its life). You *might* be able to get away with it, but resistors are cheap.
Also, if you wire it like your schematic, the power rating of the resistors will have to be increased to atleast 1 watt.

I dont see the point in having the un-armed portion if you are using the center off key switch, there really wouldnt be a difference between unarmed and off except for the green leds. but thats just my opinion, it'll work either way

__________________
Jeff Zimmerman
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

patrickredmon

Usin 2 470 ohm resistors was suggested by eblc1388, although the suggestion was the I use 2 for each LED. I am a newbie to this, so I wasn't sure that it would matter. Hence the post. Thanks for the feedback. I take it that I should stick with 2 for each LED. I think the reason for 2 was incase one failed?
There is a legal requirement that there be a seperate testing circuit and firing circuit. Again, eblc1388's suggestion was slightly different to what I posted. Not sure which is better. I would love to get rid of the 'unarmed' circuit, as it would make the key switch a lot easier to get!! But I HAVE to have it. The 2 'armed' circuits was my idea - an attempt to use fewer resistors. If you think it isn't such a good idea, I will switch back to the original.

I am not sure that this will draw the required 1Amp current. I was talking to a sparky today, and he was showing me some maths to calculate the current. Will this circuit pull the correct current??