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comet chaser


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#1 sir steve

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Posted 22 June 2009 - 09:49 PM

My I suggest a project for this club; An autonmous E match chaser. Revolution Electronics sell a small card 6 cm by 5. That has just two chips A PicAxe 18x and a ULA 2003 octal power darlington. The picaxe does not need a programmerjust 3 wires to your PC. Its huge advantage is It understands basic. The comet chaser program below tookme just an hour. As opposed to a week in ASM . The 2003 provides 8 independent Qs to sink 500mA at 48 volt. Fabulous Fireworks and our friends at Pirotecnica Europla will sponsor the project to 70 euros. in components. If you want more than 8 Ques just take Q8 into the input of another module. This is the big idea, instead of just chaining the modules they could be networked. Then if one nodefails "the show can go on." no more no fire system! I can do the electronic design. I would like someone with a nice circuit drafting package and we needa rack of 8 tubes. This is an example program shows how easy it is:
; Comet chaser Program 17/06/09 S.Humby. init:
main:
debounce:
if pin0=0 then db1
goto debounce
db1: pause 50
if pin0=0 then cont
goto debounce
cont: let pins = %00000001
pause 100
let pins = %00000000
pause 100
let pins = %00000010
pause 100
let pins = %00000000
pause 100
let pins = %00000100
pause 100
let pins = %00000000
pause 100
let pins = %00001000
pause 100
let pins = %00000000
pause 100
let pins = %00010000
pause 100
let pins = %00000000
pause 100
let pins = %00100000
pause 100
let pins = %00000000
pause 100
let pins = %01000000
pause 100
let pins = %00000000
pause 100
let pins = %10000000
pause 100
let pins = %00000000
pause 100
'loop back to start
goto main

#2 portfire

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Posted 22 June 2009 - 10:02 PM

I'm pretty sure Paul (pyromaniac303) can help with this, thats if he's not busy with other things.... BTW mate, those Transistors worked!! Great stuff

I say worked :rolleyes: , you knew they would do, and thanks for the diagram

Edited by portfire, 22 June 2009 - 10:07 PM.

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#3 pyrotrev

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Posted 23 June 2009 - 12:09 PM

Sounds a nice idea, but be careful with the output drivers. With ematches typically being an ohm or two, with a 5V supply they'll pull a few amps before they blow - it might be worth adding a bit of series resistance to protect the poor Darlingtons. PS you spell them "cues".
Trying to do something very beautiful but very dangerous very safely....

#4 sir steve

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Posted 23 June 2009 - 02:07 PM

Sounds a nice idea, but be careful with the output drivers. With ematches typically being an ohm or two, with a 5V supply they'll pull a few amps before they blow - it might be worth adding a bit of series resistance to protect the poor Darlingtons. PS you spell them "cues".



Thank you for your concern about my poor darlingtons. They will be fine, why would you want to heat up some resistors?

I dug out my old circuit it has a better idea than a safety switch. It has a shorting phono plug. You keep them in your
pocket until just ready to fire. Then no clown can arm the circuit.

I have ordered some more bits so if anyone is interested we could pop a dozen comets this summer. Fabulous
fireworks will supply the components for free if you send us the postage

Steve.

#5 Arthur Brown

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Posted 24 June 2009 - 07:02 AM

As ever with a firing system, the best parts are the finer details. Also the safety angle needs to be covered very thoroughly.

If a comet chase is going to be effective then the longest firing wire may be 50 metres or more. SO 5v is not enough to provide certain firing at the end of a 50metre wire. It is more normal to drive the logic off a 5 or 12v supply then fire the firing circuit from a 12 or 24v supply. A commercial igniter needs good access to current for firing, if the supply is weak then firing is uncertain, which goes against the maxim of 100% fire when needed and 100% NOfire at all other times.

Key arming switches and removeable links come part way but lots of other aspects help to make the system reliable in use.

Account for an amp being needed for 25milliseconds and that needing 1.5v at the igniter. Account for 100m of copper wire(that's a 50m length of twin flex) having a resistance of about 10 ohms.
SO to fire an ig at the end of a 50m length of twin flex needs about 11.5volts at the controller to do it well. Now with cat4 safety distances being large and scaled to the tube bore 50m firing wire may not be enough, so 12v may not be enough, 24v is common in pro firing controllers, 48v is possible though rarer. Commercial igs use about 50swg as the bridgewire so they fire at low energy, DIY igs never use 50swg as it isn't available easily. SO a connercial ig may fire at 500mA in 20milliseconds, a DIY ig may need 2amps for 4 seconds to fire, this is what kills cheaper firing controllers, or just causes a show to misfire.
http://www.movember.com/uk/home/

Keep mannequins and watermelons away from fireworks..they always get hurt..

#6 Spyrotechnics

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Posted 02 July 2009 - 08:01 PM

comet chases are normally fired in banks using arched stands etc for the comets/mines and as such the length of wire will be FAR shorter than 50m, probably under 2metres.

#7 Arthur Brown

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Posted 09 July 2009 - 10:17 PM

Some chases are in close proximity, others are across whole show fronts probably 30 - 50 metres.

As with all firing systems there is no specific cable length for every show so the system must cope with some wide variations.
http://www.movember.com/uk/home/

Keep mannequins and watermelons away from fireworks..they always get hurt..

#8 Spyrotechnics

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Posted 14 July 2009 - 08:45 AM

appreciate that Arthur, just if something is specifically dsigned for a comet chase section of the show then "normall" comet candles are in clusters across the site, with each cluster having its own sequencer and as such dont need long cable runs

#9 sir steve

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Posted 14 August 2009 - 03:34 PM

appreciate that Arthur, just if something is specifically dsigned for a comet chase section of the show then "normall" comet candles are in clusters across the site, with each cluster having its own sequencer and as such dont need long cable runs



I have made the comet chaser it works fine.

Steve

#10 sir steve

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Posted 14 August 2009 - 03:34 PM

appreciate that Arthur, just if something is specifically dsigned for a comet chase section of the show then "normall" comet candles are in clusters across the site, with each cluster having its own sequencer and as such dont need long cable runs



I have made the comet chaser it works fine.

Steve

#11 Arthur Brown

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Posted 17 September 2009 - 06:08 PM

Been to PLASA show (plasashow.com) recently and Skyhigh pyrotechnics had a 10 way sequencer on display. Stainless steel box with one input connector and ten output connectors and a rate control recessed nicely on the top along with a LED mimic display.
http://www.movember.com/uk/home/

Keep mannequins and watermelons away from fireworks..they always get hurt..




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