16 Rocket Semi-Simultaneous Launch Controller

[LydaRA]

I think I prefer an isolated source of a constant "flashbulb safe" current for the continuity tests. Seems safer and frees pins on the Arduino. However there are a variable number of rockets to be launched, from eight (initial "drag race") down to possibly just one or two (after replacing igniters, re-clipping leads, correcting whatever misfires...). So with variable number of parallel paths, seems each continuity test sub-circuit will need its own low-voltage/low-current power source. Right? Any suggestions for a part number (I stuck in something representative, but KiCAD had just VAC chip....but yes, wrong item for this)?

Still think we'll need some sort of amplification to distinguish the three resistance levels on the igniter...

[ttx450]

each rocket is a cue, does not matter for elc compliance maybe how you wire it.  I built a capacitive discharge firing system, that easily fires 12 in series at a 1/4 mile.  1 elc ign can draw a lot when latched and will burn out switches. I dont recommend for model rocket firing.  simple 12v battery.  I did not read the whole post.  if you need safety all go no go ck continuity ck, let me know and I'll see what notes I have

in commercial use the firing system account for resistance, by selecting amount calculated.. model rockets, you dont need to worry.. just 12v & safety ck

if you wire in parallel, good luck.. use nails and 12v car battery.

[LydaRA]

use nails and 12v car battery.

Thanks, but I cannot imagine even trying to get that through the BSA's Program Hazards Analysis.  Letting fourth and fifth graders dead short a car battery with nails cannot possibly be safer than even the sad OEM launch controllers.

[LydaRA]

Updated schematic...  Thoughts? 

[ledtester]

Some questions...

About the resistors around the MOSFET gate... any reason not to put the the 100K pull-down in between the 100R and the gate?

It seems you have a buzzer in series with the igniter. What kind of buzzer are you using?

It seems that the continuity circuit is always live. I realize there are resistors in place and you'll have other fail-safe measures, but the idea of current running through the igniter while I'm handling a rocket is a little unsettling.

[LydaRA]

About the resistors around the MOSFET gate... any reason not to put the the 100K pull-down in between the 100R and the gate?

Not that I know of.  Lesser ground to the Arduino pin or to the FET pin?  Why?

It seems you have a buzzer in series with the igniter. What kind of buzzer are you using?

Yes, not really.  Gotten a lot of push back on this.  My intent is to have a passive, "oh shit back off" warning that the igniter cable has current, should the relays weld (or anything else fail) that would put someone coming to the launchpad at risk.  But also don't want it to pollute the already tough Continuity Test measurements.  Suggestions?

It seems that the continuity circuit is always live. I realize there are resistors in place and you'll have other fail-safe measures, but the idea of current running through the igniter while I'm handling a rocket is a little unsettling.

Oh the fun of partial diagrams...  :-p   Each Pad Box will have a power switch as the first thing to "safe" when entering the launch pad area.  Seems wasteful to power the continuity test even when not reading the Arduino analog gins....especially when running this all from limited battery in a field w/o grid power available.

[LydaRA]

Updated (still partial) schematic...  Thoughts?

[LydaRA]

Getting further along with KiCAD....added more of the safety mechanisms I've discussed, but some people cannot seem to grasp.  More functionally complete, but I am sure just that many more errors in resistance calcs and component choices...

For the love of God, how does one get KiCAD to differentiate two different bus levels (12V vs 5V)?  And how does one generate a PCB, when _so_many_ components I or others reference do not exist in the library?

I'm running out of time.  Any help marking these up is GREATLY appreciated by both myself and the not-to-be-disappointed Cub Scouts!

[ttx450]

use nails and 12v car battery.

Thanks, but I cannot imagine even trying to get that through the BSA's Program Hazards Analysis.  Letting fourth and fifth graders dead short a car battery with nails cannot possibly be safer than even the sad OEM launch controllers.

use a bunch of switches?  why make it so complicated?  if you have a e match that fail to burn though can cause a latch, then more current draw. yes it could burns things out depends on how you make it.  I know of commercial systems made to run on battery 12v.

I will not share a cap discharged system, much more dangerous for you and the kids.

[LydaRA]

use a bunch of switches?  why make it so complicated

Let's see...  The OEM controller has one person (Scout/LCO) with possession of a removable plug/key/switch and a momentary button--at a mere 17 feet from the rocket burn.  That's it for OEM safety.

I've designed to still keep a removable "key" for the Scout/LCO.  But now it is a true key, with rejection & fault alarm features!  The Scout/LCO's momentary Launch button is now under a flip-cover.  Added safety, with....OMG, the "complexity" of lifting a cover!  And then I've mirrored these same _common_ safety measures with a RSO position....a second removable (real) key, and a flip-covered momentary switch.  But yeah...."oh so complicated"...."who could even understand how to operate it?"  Let's see, maybe anyone who has ever watched a movie where two men have to agree to launch the missiles?

And we can do this with the NAR-prescribed safety of 300 feet of communications cable between the Scouts and the rockets burning.  Heck, at truly safe distance, bring on a full-fledged CATO for awe & inspiration!
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Well, thanks anyway for the contribution to the efforts to inspire the children...

[ttx450]

use a bunch of switches?  why make it so complicated

Let's see...  The OEM controller has one person (Scout/LCO) with possession of a removable plug/key/switch and a momentary button--at a mere 17 feet from the rocket burn.  That's it for OEM safety.

I've designed to still keep a removable "key" for the Scout/LCO.  But now it is a true key, with rejection & fault alarm features!  The Scout/LCO's momentary Launch button is now under a flip-cover.  Added safety, with....OMG, the "complexity" of lifting a cover!  And then I've mirrored these same _common_ safety measures with a RSO position....a second removable (real) key, and a flip-covered momentary switch.  But yeah...."oh so complicated"...."who could even understand how to operate it?"  Let's see, maybe anyone who has ever watched a movie where two men have to agree to launch the missiles?

And we can do this with the NAR-prescribed safety of 300 feet of communications cable between the Scouts and the rockets burning.  Heck, at truly safe distance, bring on a full-fledged CATO for awe & inspiration!
.
.
Well, thanks anyway for the contribution to the efforts to inspire the children...

good luck I know many commercial companies that use straight 12v battery.  I been doing this prob longer then you been alive.