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Firing Sequential Ignitors with Just One Switch?

I

Ike

Jan 1, 1970
0
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.

Thank you in advance!
 
T

Tom Biasi

Jan 1, 1970
0
Ike said:
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.

Thank you in advance!
The easiest way is with a rotary switch.
Electronic step circuits are possible but you would need to examine all
failure modes for safety reasons.
You would have 10 "hot" rockets on the pad.
Fly safely,
Tom
 
I

Ike

Jan 1, 1970
0
Hi Tim...

I'm really looking for a way to chain any number of ignitors, not just
10. One button is pressed, and the first ignitor in the chain is lit
and blown off the chain (electrically speaking), then the button is
pressed and the next ignitor in the chain is lit, and so on.

Thanks!
 
C

Christian Brunschen

Jan 1, 1970
0
Hi Tim...

I'm really looking for a way to chain any number of ignitors, not just
10. One button is pressed, and the first ignitor in the chain is lit
and blown off the chain (electrically speaking), then the button is
pressed and the next ignitor in the chain is lit, and so on.

Here's a thought that occurred to me - it's probably a bad idea, but I'd
like to have it shot down professionally.

Construct a number of independant counters - each initialized with the
sequence number of the igniter, and set to actually ignite when and only
when the counter reaches zero.

Connect all your counters to a shared bus, and make it so that pushing the
button signals all counters simultaneously to 'count down one step'. Thus,
evey time you press the button, another counter will reach zero, and that
counter will then ignite its rocket.

You can, in this setup, even configure several counters to fire
simultaneously, simply by setting them to the same sequence number.

You could even then have a completely automatic launching sequence, simply
by replacing your button with a 555 or similar.

As everything is nice and modular, you could start out with modules that
use a four-bit counter (which will allow for a max of 15 distinct launch
events), and later add wider ones if necessary, while the narrower ones
still retain their usefulness.

Each counter module would need a counter, a way to pre-set the value, and
perhaps a small display to display the current remaining count just so you
can check things are as they should be.

Let the shooting-down begin!

Best wishes,

// Christian Brunschen
 
S

Stephan Urban

Jan 1, 1970
0
Here's a thought that occurred to me - it's probably a bad idea, but I'd
like to have it shot down professionally.

Construct a number of independant counters - each initialized with the
sequence number of the igniter, and set to actually ignite when and only
when the counter reaches zero.

Connect all your counters to a shared bus, and make it so that pushing the
button signals all counters simultaneously to 'count down one step'. Thus,
evey time you press the button, another counter will reach zero, and that
counter will then ignite its rocket.

You can, in this setup, even configure several counters to fire
simultaneously, simply by setting them to the same sequence number.

You could even then have a completely automatic launching sequence, simply
by replacing your button with a 555 or similar.

As everything is nice and modular, you could start out with modules that
use a four-bit counter (which will allow for a max of 15 distinct launch
events), and later add wider ones if necessary, while the narrower ones
still retain their usefulness.

Each counter module would need a counter, a way to pre-set the value, and
perhaps a small display to display the current remaining count just so you
can check things are as they should be.

Sounds a nice idea, I'd say.
And don't forget a main switch, perhaps a keyswitch, for the ignition
circuit only so you can set the counters without running the risk of
igniting anything by writing a 0 in one of them. ;)

**** Stephan ****
 
E

ehsjr

Jan 1, 1970
0
Christian said:
Here's a thought that occurred to me - it's probably a bad idea, but I'd
like to have it shot down professionally.

Construct a number of independant counters - each initialized with the
sequence number of the igniter, and set to actually ignite when and only
when the counter reaches zero.

Connect all your counters to a shared bus, and make it so that pushing the
button signals all counters simultaneously to 'count down one step'. Thus,
evey time you press the button, another counter will reach zero, and that
counter will then ignite its rocket.

You can, in this setup, even configure several counters to fire
simultaneously, simply by setting them to the same sequence number.

You could even then have a completely automatic launching sequence, simply
by replacing your button with a 555 or similar.

As everything is nice and modular, you could start out with modules that
use a four-bit counter (which will allow for a max of 15 distinct launch
events), and later add wider ones if necessary, while the narrower ones
still retain their usefulness.

Each counter module would need a counter, a way to pre-set the value, and
perhaps a small display to display the current remaining count just so you
can check things are as they should be.

Let the shooting-down begin!




Best wishes,

// Christian Brunschen

Good idea - but you don't need a counter for each igniter.
Use a decade counter - like a 4017 - and each press of the
switch will increment the count by 1. One chip will count
from 0 to 9 with an individual output for each count. He
can add as many counters as he needs to count from 1 to N,
with each chip controlling 9 igniters.
The pushbutton will need a debounce circuit - cross connected
nand's can do that. I don't know what current the igniters
need, but I expect he'll need a transistor on each output to
fire them.

A sample 4017 circuit is shown here:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#shift.gif
Look for 18 stage LED sequencer.

Personally, I would use the rotary switch approach to select
the rocket, and a pushbutton to fire it. He could add as many
rotary switches as needed to select N rockets. That way, it
takes two operations to fire a rocket - 1) select the rocket to
be fired and 2) push the button. Seems safer that way.

Ed
 
M

mike

Jan 1, 1970
0
Ike said:
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.

Thank you in advance!

This sounds like a trip to the emergency room just waiting to happen.

You really, REALLY, need to know EXACTLY which ignitor will fire when
you push the button. Don't skimp on the status readouts if you
do it with a PIC. AVOID hairbrained lashed together logic.
All it takes is one missed switch bounce to fire the wrong rocket.

The easiest and safest might be a row of 10 pushbuttons. If you need more,
bank switch the ten buttons with a rotary switch.
mike...I hate emergency rooms...

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
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Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
 
C

Captain Dondo

Jan 1, 1970
0
Ike said:
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.

Thank you in advance!

I don't know what your budget is, but a basic PLC - like the pico from
A-B - can do that along with inputs from safety observers with kill
switches. It has the dry relay contacts to provide the power handling,
too. And a nifty little LCD display you can program to show the
countdown.....

I'd guess less than $100 for the PLC and a handful of pushbuttons. I
think a pico has 12 dry relay contacts. You'd have to chain them
together to get more....

For a low-tech alternative, see the nail-and-wire pegboards the
fireworks guys use. Basically, a bunch of 12 penny nails with wires;
you hit each one in turn to fire the next sequence of fireworks.
 
B

Bob Monsen

Jan 1, 1970
0
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.

Thank you in advance!

One way to do this safely would be for each rocket to physically close a
switch as it goes, making the next one hot. Perhaps a little pin/string
arrangement might work? A nonconductive pin holds two contacts apart. Once
the pin is pulled, the contacts close, and the next one is ready.
There are a few issues to work out here (like not launching two rockets
when you only wanted to do one), but it is probably simple to do, and
practically free.
 
J

Jasen Betts

Jan 1, 1970
0
Hello...

I'm working with the electrically-fired nichrome rocket ignitors for a
rocketry project.

Is there a way to wire a number of ignitors to a single switch so that
each time you close the switch it activates the next ignitor in the
chain, burning it up, and somehow making the next ignitor ready for
electrical activation? This would allow, for example, 10 rockets to be
fired in succession by pressing the button 10 times.

I DON'T want to push the button once and fire all 10 electric matches!

If there isn't a way to do this, I will continue with my plan to use a
PIC microprocessor, but that means relays and/or transistors and more
cost if I wanted to control more than 5 or 10 ignitors.


If you can get hold of an old rotary selector from an old electromechanical
phone exchange that'd do the trick... (with the one I had you could switch
50 ignitors sequentially) electromech is two generations ago so they may
be rare even in the best stocked surplus outlets, the one I had needed
48V to fire the solenoid but was easily dissasembled (all bolts, no rivets)
and could have been re-wound for 12 or 6V operation with only hand tools
and a bench vice...



if you go with the microcontroller you can matrix the output
so that 10 output devices (relays/transistors etc) can control 25 igniters,
do 5 rows and 5 columns with a diode in series with each ignitor.

you could also use a decade counter (two for a matrix) instead of the
microcontroller that may save you a few bucks.

a ULN2003 driver chip may be cheaper than 8 transistors, (but not in the
catalogue I have here)

hmm, if you want cheap driver hardware dissasemmble an old 24-pin dot matrix
printer :) 24 pin drivers and 4 drivers each for the two motors...



Another possibility would be using some contacts that close when the rocket
departs so that the next ignitor is connected to the circuit, you'd need to
set your button up to send only a short pulse so you don't get accidental
multiple launches.

+V -----------------------+ +--------------->
|nc |
|| __o |
+---||------o-~~ |
| || com o---+---/\/\/\--+ to ignitors
| no |
| |
0V -----+---------------------------------+--->


the optimum component values depend on the specifications of the ignitors.

Bye.
Jasen
 
Q

quietguy

Jan 1, 1970
0
It seems to me that there is a time to buggerise around,and a time to go safe
and simple - I reckon firing rockets should be safe, simple, and with minimum
error risks

Another poster suggested a rotary switch to select the rocket, and a pb switch
to fire - sounds like the best safe and simple way to go safely

David
 
B

BobG

Jan 1, 1970
0
Seems like timed charges get used in these building demolitions. They
really dont want one of the charges to hang and stop the process once
started, so I believe there are standard procedures and protocols that
are proven effective in this area, I just don't know if a demo expert
would tell us, because then he'd have to whack us.
 
J

John Fields

Jan 1, 1970
0
It seems to me that there is a time to buggerise around,and a time to go safe
and simple - I reckon firing rockets should be safe, simple, and with minimum
error risks

Another poster suggested a rotary switch to select the rocket, and a pb switch
to fire - sounds like the best safe and simple way to go safely

---
I'd go with a pushbutton for each rocket and a separate momentary
spring-loaded "ARM" toggle switch under a switchguard to enable the
array of pushbuttons:


ARM
+V>--O---> |
|
O---> |
| |
| O---[IGNITER 1]---+
| |
| |
O---> | |
| | |
| O---[IGNITER 2]---+
| |
. |
. |
. |
| |
O---> | |
| |
O---[IGNITER n]---+
|
RETURN>----------------------------+
 
B

BobG

Jan 1, 1970
0
JF:
I'd go with a pushbutton for each rocket and a separate momentary
spring-loaded "ARM" toggle switch under a switchguard to enable the
array of pushbuttons:
============================
Elegant
 
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