Hello from Victoria BC

Welcome!  My first Arduino project was to figure out & restore a hand-built weaving loom--driven by a PC full of patterns, and an Arduino to control the Dobby.  My degree was in CompSci & Math.  Small world...

@lydara

Interesting, I had to look up Dobby 🙂 Did the Arduino perform the same function as a Jacquard loom pushed card ?

I started getting into programming only after I found out that there aren't many positions for just mathematicians :))

@will  Pretty much.  Solenoids thrust pins into the path of the knife operated by the treadles.  So the some of the frames get raised, others not.

The PC outputs a pattern.  The Arduino interprets that pattern into which solenoids to stroke when, as the treadle moves for input, then asks the PC for the next pattern.

My usage for math these days is in multiplying the number of rockets the local Cub Scouts can fly--and so multiplying smiles!  I'm currently at ten-at-a-time banked sets of 20-at-a-time mounted....hundreds every day for two weeks each July!  😀  Check another thread for the five pages of electrical schematic I'm here seeking input on...)

Less profitable (well actually the donation is _costing_ me) but more fun than the I.T. day job (which I love also).

@lydara

I've read it and looked at the schematics, but I don't know enough about rocketry (and the safety issues) to have any useful opinions  or suggestions.

How much current does each rocket require for the igniter and how many will fire simultaneously ?

@will  IT depends upon how many Scouts choose to press their individual Launch buttons!  The RSO & Countdown Clock enable/disable the window of time where the children can launch.  We all count down, but sometimes a "control freak" will delay a couple of seconds (to call attention to himself, to prove _he_ has control.

Each Estes rocket igniter needs 12V 2A to fire.  So each PadBox (hosting 10 rockets) will need to provide 12V 20A to the parallel igniters, plus about 1A to the logic & control stuff.

@lydara

That's a lot of current, now I understand why there was a discussion of wire gauge. Must take a lot of battery charging (or a big generator) to supply enough power for the afternoon.

@will  Figuring it'll take some motorcycle or truck batteries.  Good news is that it only has to source current for a few seconds a few times per hour.   Can recharge overnight, or hopefully just once per week.

@lydara

If you don't need all of the launchers to go at the exact same moment, you could switch the rocket igniter circuits 'on' when the countdown timer gets to zero (and all safety precautions satisfied) and leave it hot for a couple of seconds (to let all the kids launch).

That might discourage the "control freaks" since if they waited past the hot time, they couldn't launch until their next turn.

It might also help to spread the extremely heavy instantaneous load on the battery, since it could spread the current draw out in time. It's unlikely that all 10 kids would hit the launch button simultaneously.

@will  Exactly.  We countdown together, but human reflexes vary.  The allowed window will be from 1/2 second early to 2 seconds late.  Individual button presses would delay current, igniters burning through would stop current.  So somewhat varied.

@lydara

I don't understand why individual button presses would "delay" current ?

Wouldn't the button press trigger delivery of current to the igniter (all safeties considered) ?

@will  If someone presses early, then their channel's current starts early.  If they delay the button press, then their channel's current delays.

@lydara

I think it's clear in my mind that I don't know enough about this topic to be of much use. I'm going to go reread the existing thread and check out the diagrams to see if I can wrap my head around it. 

It's probably better to move this discussion back to the original topic anyway so others can check it out too. If I have more questions or comments, I'll reply back to that topic to keep it all together.

Thanks