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need help with my Electronic firework ignition system

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darylrose

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hi guys, im trying to make an ignition system for fireworks, but im having a bit of a problem with my circuit.

i am using a key switch, toggle switch and finally a push button to trigger a 4017B decade counter microchip to move to its next output. on these outputs are home made E-Matches, these are no problem at the moment, im more concerned about getting the circuit to work properly first. The problem i hve is when i turn the toggle switch to on the output 0 on the 4017B chip turns high, i dont want it to be high unless the push button is pressed. i also read that if there is no signal going into pin 14 then it should be anchored to negative, i think i can do that with a transistor, but im not sure what one to use. i order all my parts from Leading UK distributor of electronic components, tools, production equipment, electrical spares and educational products., so if anyone can help and find the part i need, i would be very very greatfull.
ive added some drawings and pictures to help you get the idea of what im doing, hope you can help.
Daryl
 

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Several points here.

I assume that you want the 4017 to sequence from one firework to another. If so, you have to leave it powered so that it remembers where it has got to. You key switch should power it and leave it powered, and you should have a reset circuit so that output "0" is on at the start.

The 4017 has no way of turning off all of the outputs, so you can only wire 9 fireworks to it, and leave the "0" output unconnected. You can't remove the power from the 4017 while there is power connected to the clock input. The data sheet says:-
Input Voltage (VIN) -0.5 VDC to VDD +0.5 VDC
which means that the input voltages must within the range of the supply or just a little outside that range. There are input clamping diodes so if you try to break that rule, things will go wrong. I've been there, blown the ICs.

I don't see why you want three switches. You can have a master key and a pushbutton that moves on to the next firework. There is no need to stop firing a firework. You can leave power onto firework 1 while you are admiring the effect and waiting for the right time to fire number 2

You need to debounce the switches.

You need series resistors for the LEDs.

You could save a lot of effort and probably some money with this:-
**broken link removed**
 
erm, ok =s
it was a little project of mine just for a bit of fun, i didnt know if i t would wwork but obviously its not as simple as i first thought.
buying a pre-made one completley avoids the point of me doing this to be honest.
Do you think what i'm doing is actually possible?
the idea of 3 switches was a bit over the top but it looked cool, i plan to use the key to turn it on, and the key wont be turned off until im packing the kit away for the next year, the toggle switch once turned on wont get turned off untill the fireworks are done either, the only button that will be used during the display is the push button, which will be used to change to the next firework.

How do you debounce the switches?
and the LED's are 12v at the moment so i dont need any resistors, however i will change them to save power if it comes down to it.

hope that makes it a bit easier to understand
Thanks, Daryl
 
Last edited:
ok, ive finished the control box which houses the switches and the 3 LEDs, ive done some tests and found out that after the toggle switch it switched to on, we have almost 9v between the + and - which is good, and 0.3v on the signal line, i have a suspicion that this is the cause of the IC turning on automatically. i think what i want here is a device that decides when the voltage is a bove a certain point to switch from negative to positive, i think its a transistor, but im not sure which one to use atall
thanks, daryl
 
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