ideas needed for fire work display

[nicky]

I have been asked to build a timer to let of 10 fireworks with an adjustable delay roughly 0.5 to 2sec between them, from the touch of a button. It sounded easy at first but i am struggling. i can build a timer using a 555 which i thought i could trigger a 4017 but i cant seem to vary the outputs i have tried using adifferent c/r on each output but it does not seem to make any difference. (i think im doing it wrong) i have tried usung a j-k flipflop but still cant get the sequence right and i would need a lot of them. any help would be greatly appreciated.

 

[grrr_arrghh]

the easiest way would be to use a PIC, that way, you could specify the delay bewtween each output going high.

However, if you don't want to get into microcontrollers, there are other ways.

One that comes to mind, is to use many 4017s linked together, so that the first one cycles through all its outputs, then the next one does it, so you would have maybe 100 outputs going off in sequence, all with the same delay between them. If you made this delay 0.5 secs each (for example), you could have delays in multiples of 0.5.

For example, you want the second firework to go off 1 second after the first, so you connect it to the thrid output, because the seqence would take 0.5s to get to the second output, then another 0.5s to get to the third, totalling 1second.

I havn't explained it very well, do you understand what I am trying to say?

Tim

 

[Roff]

I have been asked to build a timer to let of 10 fireworks with an adjustable delay roughly 0.5 to 2sec between them, from the touch of a button. It sounded easy at first but i am struggling. i can build a timer using a 555 which i thought i could trigger a 4017 but i cant seem to vary the outputs i have tried using adifferent c/r on each output but it does not seem to make any difference. (i think im doing it wrong) i have tried usung a j-k flipflop but still cant get the sequence right and i would need a lot of them. any help would be greatly appreciated.

Do you want the delay of each output to be individually adjustable (use a PIC), or do you want adjustable but uniform delays for all 10 outputs (555 + 4017)?

 

[nicky]

Thank you for the relpy. In answer to your question i would like 'adjustable but uniform delay for all 10 outputs'. I have tried the suggestion that i use a couple of 4017's i have used output Q0 & Q9 with leds & the flashing is still to fast. I dont know enough about pic's to try doing it that way though i wish i did. Haven't had time to try out the above with different clock pulses due to the fact work keepsgetting in the way.Thank you again for trying to help.

 

[pike]

simply solder a bigger timing capacitor in place of the old one.

 

[nicky]

I feel a bit stupid now. The reason i couldn't slow down the timing rate of the led's was because i followed the diagram for the channel light bulb sequencer but it didn't have the connection for +v on the 4017 and i didn't think to check. now i have put that in place it all works fine. Thank you for the ideas though the pic site was good and it was a brilliant idea to lin up more 4017's for more outputs as i know that will be the next question.