![IMG_0180[2401].JPG](jpgKcZmvlYwwC.jpg){kind=link}
Thank you for posting the link James. Really good read. The info for figure 4
was interesting and showed the “conduction current of the gas plasma produced
by the burning pyrogen.” Also, the section on using 9 volt batteries was good.
Hopefully, I can go a little OT now and ask about the wiring for some miniature
solenoids I’ve acquired. Please see the attached photo. The solenoid has a
marking that it can be powered by 22 to 30 VDC. The wires are yellow and
brown. Do you know what the polarity would be? Also, there’s a small resistor
across the leads. Without me guessing, what is the purpose of this resistor
and should the solenoid work without it? Is this the kind of thing that may
improve the performance of e-matches?
Thank you,
Richard Dierking
From: James Dougherty<mailto:jafrado@xxxxxxxxx>
Sent: Tuesday, January 24, 2017 9:22 PM
To: ROC Chat<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
And yeah Richard, what Kurt said.
On Tue, Jan 24, 2017 at 9:21 PM, James Dougherty
<jafrado@xxxxxxxxx<mailto:jafrado@xxxxxxxxx>> wrote:
hey great thread.
Old. but good - not sure if you guys read Rob's ignitor testing ...
https://web.archive.org/web/20121119015627/http://www.gwiz-partners.com/igniters.pdf
You'll find the DF N28F is very much equivalent to an MJG J-tek and there is a
good
reason for that - your standard Automotive airbag used to have 2 of these
babies in it.
Kind of crazy when you think that in an accident you're Airbag deployment is
relying
on 2 Ohms of load and a one dollar e-match. :-)
On Tue, Jan 24, 2017 at 3:23 PM, Chris Spurgeon
<chris@xxxxxxxxxxxxxxxxx<mailto:chris@xxxxxxxxxxxxxxxxx>> wrote:
I wonder if it could also be the case that at the instant when one of the
igniters burns through, all of them are already so hot that they’ve reached a
point of no return and are going to ignite even without further electric
current?
On Jan 24, 2017, at 1:02 PM, R Dierking
<applerocketry@xxxxxxxxxxx<mailto:applerocketry@xxxxxxxxxxx>> wrote:
Yup, I know, hard to believe series is better. But, it is. It took a lot of
convincing (Allen) and testing for me to swallow that, but it works great.
However, you have to test before you launch! I provided test points on the
airframe to test the amount of resistance of the series before launching.
Now, if I could only get the damn hatch to blow off. ☹
From: Alexander Jones<mailto:uscjones@xxxxxxxxx>
Sent: Tuesday, January 24, 2017 12:06 PM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Cc: R Dierking<mailto:applerocketry@xxxxxxxxxxx>; Chris J
Kobel<mailto:chris.j.kobel@xxxxxxxx>
Subject: Re: [roc-chat] Re: Resistance for Electric Matches
Excuse me if I'm misunderstanding the situation, but wouldn't it be a bad idea
to wire them in series? Bc they're designed to kill their own circuit (or at
least add a LOT of resistance to it) when they blow, so if you're trying to get
more than one charge to blow, and they're not backups to each other (i.e. you
need all of them to fire), you'd have one blow, then the current would drop
drastically across the other two and they may not fire....I would think it'd be
better to wire them in parallel so they all have current available to them at
all times, then just limit the current with a resistor, or, if your concern is
destruction of your electronics, then put some other kind of current limitation
circuitry in the line.... something like this:
http://www.instructables.com/id/World-simpliest-DC-current-limiter/ ....if you ;
don't want to drag yourself through the math to get the fixed resistor value
analytically (so you don't have a potentiometer in your rocket), you could
build the circuit first with the potentiometer in place to determine what
resistance = the current you want, then replace it with an equivalent
fixed-value resistor. It's a decent amount of work, but it's better than
destruction of your avionics board due to overcurrent or a recovery system
failure on what I assume is a pretty big project, if it has 3 parachutes.
....or just check and see if your avionics board has a current limiter or
overcurrent protection built in....some of them do.
On Tue, Jan 24, 2017 at 11:43 AM, Adrian P. Bailey
<adrian@xxxxxxxxxxxxxxx<mailto:adrian@xxxxxxxxxxxxxxx>> wrote:
This may be a silly question but have you tested the resistance of the test
leads (by holding the ends together)… ;)
From: R Dierking
[mailto:applerocketry@xxxxxxxxxxx<mailto:applerocketry@xxxxxxxxxxx>]
Sent: Tuesday, January 24, 2017 11:41 AM
To: Adrian P. Bailey <adrian@xxxxxxxxxxxxxxx<mailto:adrian@xxxxxxxxxxxxxxx>>;
roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>; Chris J Kobel
<chris.j.kobel@xxxxxxxx<mailto:chris.j.kobel@xxxxxxxx>>
Subject: RE: [roc-chat] Re: Resistance for Electric Matches
Looks like the San Marcos store for me.
Are Cat 3 test leads OK for our purposes? Perhaps I just need better test
leads with clips?
From: Adrian P. Bailey<mailto:adrian@xxxxxxxxxxxxxxx>
Sent: Tuesday, January 24, 2017 11:25 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>; Chris J
Kobel<mailto:chris.j.kobel@xxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
Fry’s in Woodland Hills has quite a selection. Check online – it will tell you
what they have in the store nearest you: http://www.frys.com/
From: roc-chat-bounce@xxxxxxxxxxxxx<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx] On Behalf Of R Dierking
Sent: Tuesday, January 24, 2017 11:20 AM
To: Chris J Kobel <chris.j.kobel@xxxxxxxx<mailto:chris.j.kobel@xxxxxxxx>>;
roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
OK, JK, but RSO’s, if you ever see wires sticking out of one of Chris’s
rockets… 😲
He does know his igniters!!!
So, glad I asked about this before conducting my ground test. I had 2 matches
with 1.6 ohms and one that was 3.2 ohms that would have invalided my test.
Particularly bad if I would have found out about this later.
Learned: When doing multiple charges in series measure each match (or
igniter), and then all together to check for problems.
Going OT a bit, but does a place like Fry’s have a good selection of meters? I
wonder if I can get a meter that reads resistance better. Maybe the leads have
to be higher quality too?
From: Chris J Kobel<mailto:chris.j.kobel@xxxxxxxx>
Sent: Tuesday, January 24, 2017 10:53 AM
To: R Dierking<mailto:applerocketry@xxxxxxxxxxx>;
roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: RE: [roc-chat] Re: Resistance for Electric Matches
Sticks and stones….
From: R Dierking [mailto:applerocketry@xxxxxxxxxxx]
Sent: Tuesday, January 24, 2017 10:51 AM
To: Chris J Kobel <chris.j.kobel@xxxxxxxx<mailto:chris.j.kobel@xxxxxxxx>>;
roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: RE: [roc-chat] Re: Resistance for Electric Matches
Wow, not bad for a wire twister Chris. 😊
From: Chris J Kobel<mailto:chris.j.kobel@xxxxxxxx>
Sent: Tuesday, January 24, 2017 10:33 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
Some info on igniters that I gathered a few years back.
Chris
From: roc-chat-bounce@xxxxxxxxxxxxx<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx] On Behalf Of R Dierking
Sent: Tuesday, January 24, 2017 10:08 AM
To: Andrew Wimmer <xenonrocket@xxxxxxxxx<mailto:xenonrocket@xxxxxxxxx>>;
roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
To be honest, I don’t know the brand. They are not in the box. They are
however the same color lead wire (black) and appear to be the same make. A
single one is 3.2 ohms.
Richard
From: Andrew Wimmer<mailto:xenonrocket@xxxxxxxxx>
Sent: Tuesday, January 24, 2017 9:56 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
What brand electric match?
3 in series should have 3 times the resistance of a single match.
http://www.pyromate.com/Basics-of-Electrical-Firing.htm
-Andrew
On Tue, Jan 24, 2017 at 9:45 AM, R Dierking
<applerocketry@xxxxxxxxxxx<mailto:applerocketry@xxxxxxxxxxx>> wrote:
What’s a good range for the resistance of electric matches?
For my project, there will be 3 parachutes deployed from separate side-bays and
initiating the charges at apogee.
Connecting the matches up in series and testing today.
I know the resistance will go up with the series connections, but would like to
get an idea what the range should be.
Thank you,
Richard Dierking
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