Pyrotechnic Timing Device

[4pyros]

Edit: What sort of pyrotechnic displays involving mainframe printers do you put on ??

Working with mainframe printers was one of my old jobs.

 

[alec_t]

If you're determined to have a LED current ~ 20mA, here's a front end for the timer which will give you that, with an input of anything from 6V to 50V. At 36V the whole front end dissipates only ~ 1.2W even when the input is indefinite.
In the simulation, V2 provides a burst of high frequency 250V pulses to represent noise spikes. The graphs respectively show Q1 collector current (= LED current) as a function of input voltage and in the presence of the noise spikes.
The varistor action is not simulated here but in practice would suppress spikes above 65V. Ignore the connections shown for the opto-transistor (which are there only to keep the simulator happy). I've attached the simulator asc file, if anyone wants to play.

 

[Reloadron]

Looking forward to seeing what you dig up.

I found one of these but the damn thing is powered by 120 VAC. I know I had some similar either Amtek NCC or Macromatic manufacture that were either 12 or 24 VDC powered. I'll continue to rummage through my junk. Continue to pursue the nice drawings Alec has provided till I can dig a little more. Someday before I die I really need some organization around here.

Ron

 

[4pyros]

If you're determined to have a LED current ~ 20mA,

No Alec I am not. Just wondering what the best design practice would be. I gess it's different for a known load than for an unknown load.
It this point I am thinking of making the firing system interface more universal so it can be uesd on other projects as well. Sorry I did not bring that up before, but with that in mind what current would you use for the 4N35 LED?
Thanks for the work on the new front end. But I think if I was to go that far I would just use a regulater. The 7805 is good up to 35 Volts, with the diode drops it would work for an input voltage of 36 volts but not much room for error. What do you think about using a regulater to save some parts? Maybe a current regulater chip?
Andy

 

[4pyros]

Ron; Thanks for digging. I need to clean up my stuff to, but only someday. LOL
I am going try try this dual stage timer I fould on the web;
https://www.canakit.com/catalogsearch/result/?q=ck249m2&x=21&y=14
For prototyping, I may need a change a cap or resister to get 1/2 sec timing but I have not seen a skematic for it yet. I hope its close to the one Alec came up with if not hopefully I can change it easly.
Andy

 

[Reloadron]

Cool Andy, let us know how it works out. Hell, I doubt I could build the thing for what they sell it for in time and patience.

Don't you just love things that explode?

Ron

 

[alec_t]

What do you think about using a regulater to save some parts? Maybe a current regulater chip?

I've never used a current regulator IC, but a 7805 would require caps front and back so there wouldn't be a great saving on parts, especially if you incorporate noise/suppression components as I did (and which I think would be essential if the trigger is destined for wider application). By my reckoning the only saving would be the zener and the base bias resistor.

Edit: What voltage range does that dual stage timer work in?

 

[4pyros]

Hell, I doubt I could build the thing for what they sell it for in time and patience.

Thats what I thought and the owner of the fireworks company agreded. I took a long time to find it.
Andy

 

[4pyros]

What voltage range does that dual stage timer work in

It has a bridge rectifier and is rated at 9VAC or 12VDC. I am hoping I can rewire (mod) the bridge to work as the trigger input and run it off the 12 volt batterys.
Andy

 

[4pyros]

Don't you just love things that explode?

I love the smell after a show!!

 

[alec_t]

It this point I am thinking of making the firing system interface more universal so it can be uesd on other projects as well. Sorry I did not bring that up before, but with that in mind what current would you use for the 4N35 LED?

I think post #39 answers that.

 

[4pyros]

I just got my two stage timer modules from Cana Kit. Thay are vary close to alec's drawing in post #17. The resets are wired different to provide a power on reset option. Still waiting for the firing system interface parts. I will let you know. Andy

 

[alec_t]

Thay are vary close to alec's drawing in post #17. The resets are wired different to provide a power on reset option.

Power-on reset is provided in my post #21 circuit.

 

[4pyros]

alec; Thats not the way thay did it. there is no transister. Both reset pins are tied togher and go to a high side (pull up) resister with a cap to ground.

 

[alec_t]

Fair enough, and certainly simpler (cheaper!), but the transistor is there as an added precaution. A bit of a luxury, perhaps. As I said previously, "Q1 has been added to prevent spurious motor turn-on during the 1/2 sec delay."

 

[4pyros]

Thanks alec; I should have my trigger parts tomorrow so I can start making that. I have been working on the motors and wheels and poles. I will keep you all posted and maybe some video of the first try. Andy

 

[4pyros]

Update; Cana Kit Timer Price Incress

It seems Cana Kit had a typo on the web site for the timers I am using;
https://www.canakit.com/2-minute-dual-delaying-adjustable-timer-kit-ck249m2-uk249m2.html
I got them for under $10 and now thay are $24.
I got 5 at a real good price!

 

[alec_t]

Nice deal!

 

[4pyros]

Timer Update

The Cana Kit timer is working nicely. I changed the cap for the 1st stage from 10uf to 1uf and I get about 1/2 delay at mid scale on the pot. The 2nd stage is giving me about 1 min mid scale. The kits came with a power on trigger option with a jumper that connects a cap and resister from ground to the triger input of the 555 that I am not using. As part of the
power on trigger option I think thay added a pull up resister to the trigger blocking cap on the chip side so now the trigger blocking cap has pull ups on both sides. I left it thare thinking it would help prevent false triggers something like Alec_t was trying to do in his revised circuit. do you guys have anythoughts on having pull ups on both sides of the trigger blocking cap?
I will do a hand drawing of the kit timer soon.
Andy

 

[4pyros]

Pyro Trigger Interface Update

I made one of my trigger circuits for testing using the dropping resister and zener diode. I had problems with the test current of the firring systems. Thay all use a small current ( under 20ma )to test for continuity of an E match. Our wireless system false triggered the interface and the FireOne system was reading continuity all the time. So much for the easy way out. I have orderd 7805s regs to try like the interface we have that works fine. I also ordered input and output caps for the reg but the interface we have does not have them. Any thoughts as to whether I really need them for this applicashoin?
Thanks Andy