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#1 Guest_PyroPDC_*

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Posted 05 March 2012 - 07:40 PM

knowing there's a lot of electronic wizards on here im hoping someone might help me.

i current have a firebywire firing system which outputs a pulse 24v and i need a way to switch on a 4 Amp 240v device which controls a water pump / air blower for a projection screen system.

the problem i have is i need a way so when it send 24v it will switch on the relay / transistor but also switch it of if the same when 24v is sent again. also since firebywire has a test current of <30ma it would also need a resistor ect to stop the test current from activating the circuit.

any ideas ?

#2 Arthur Brown

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Posted 05 March 2012 - 07:43 PM

Have you asked Matt at FBW? He knows all there is to know about how to make compatible things for FBW!
http://www.movember.com/uk/home/

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

#3 cooperman435

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Posted 05 March 2012 - 09:13 PM

Im sure Matt would be able to help, or as its a standard serial protocol you may be able to make a "reciever" or imitation sequencer for FBW that accepts just an on and off signal?

#4 Arthur Brown

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Posted 05 March 2012 - 09:23 PM

I can see easy ways to have a circuit that would "test" safely and operate on the fire command, then it could latch or not as needed. I remain uncertain whether FBW can send the same cue again in a show, so you may need to use one cue to latch on and another cue to latch off afterwards. Getting the correct isolation between the 24v cct and the 240v cct may not be easy especially in the half damp of a wet november show. Some of the details needed for this need to come from FBW officially so Matt would be my first point of call.
http://www.movember.com/uk/home/

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

#5 Guest_PyroPDC_*

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Posted 05 March 2012 - 10:06 PM

software wise the new version to use the same cue more than once is coming out very soon, dampness wont be a problem as i can make sure its all ip55 rated.

as for a device using standard serial protocol i dont think that would work as it would need mats FBW firmware for the firebywire software to talk to it, and i dont think mat would allow that to be given out. will send a pm to mat though as i dont tknow if i could make a simple serial device that i can address and accept 1 command from firebywire as if it was 1 cue, it wont be able to talk to firebywire but (testing ect) but it may still recive a command)if i knew what commands its uses

Edited by PyroPDC, 05 March 2012 - 10:58 PM.


#6 Arthur Brown

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Posted 05 March 2012 - 10:14 PM

I'd be looking at a relay that would pull in at 100mA and possibly latch, it would test OK as the pre show test runs, and would pull in on a fir command (the DC pulse) it would then need to latch and have another cue do the unlatch command.

The issue with waterproofing is not the case rating but the risk of condensation getting on the relay pcb and mains tracking onto the 24v side and frying something expensive (and stopping the show)
http://www.movember.com/uk/home/

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

#7 digger

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Posted 05 March 2012 - 10:37 PM

This can be achieved with a simple logic circuit and either a relay as pointed out or a triac or two if you get adventurous.

The other way would be to use a PIC microcontroler (yes also logoc), then you can play any tune you want with the input(s)/output(s). I would not worry about the 30ma test current it just depends on how you set up the input stage.

However for simplicity something like the following could be easily adapted with the use of a couple of extra resistors (potential divider)CLICK ME
Phew that was close.

#8 Guest_PyroPDC_*

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Posted 06 March 2012 - 01:25 AM

thanks digger that looks perfect for what i need :D

#9 CCH Concepts

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Posted 07 March 2012 - 09:34 AM

i was going to reply, but it would seem digger said everything i was going too. lol

the only thing you could add is a low side current sensing op amp, basically it measures the voltage drop over a resistor and you can use the output to drive your relay. idea being when the current supplied is below say 50mA the output is low and if it above its high.

here's a quick link i found but I'm sure there more out there to give a better description.

Current sensing op amp.


#10 mlepyro

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Posted 11 March 2012 - 09:36 PM

Paul,

Try searching for "Latching Relay"

We have done something similar to turn halogen lights on before.

Cheers

Mat
MLE Pyrotechnics Limited
www.mlepyro.co.uk www.firebywire.co.uk




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