best place to get e-matches?

It's been a long time since I bought e-matches and now all that seems to be available is dip yourself kits which I am not looking for. Anyone know where to get good ready to roll e-matches? Thanks!

While technically not an e-match, this is the closest that you can easily get without making your own.

https://www.questaerospace.com/cgi-bin/commerce.exe?preadd=action&key=Q2G2_8IN_LONG_2_IGNI

Greg

The cat's pajamas right here:
https://www.wildmanrocketry.com/ShowProducts.aspx?Class=846&Sub=848

The undipped blanks from American Pyro work well for lighting BP too, but I only use them in redundant systems.

chadrog said:

The cat's pajamas right here:
https://www.wildmanrocketry.com/ShowProducts.aspx?Class=846&Sub=848

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An ematch by any other name still works as well. And is still a regulated product.

KO

So no one makes them anymore because they are "regulated". What does that mean? Gone are the days of buying Daveyfires by the truckload?

Our club has a LEUP and we buy ready-to-go ematches from https://electricmatch.com/

I see he is now selling a dipping kit for hobby rocketry use...

Nope, MJG is still in business, and doing well. I understand that Jeff G. sold the company to Seminole (wire manufacturers), but they are still widely used. Their prices on duplex wire are excellent.

Daveyfire took their ematches off the consumer market years ago. I don't know who does use them these days, but in the pyro world we either get MJGs or the Chinese matches with the thin, colored insulation (pink/orange/green/black/blue)

KO

Daveyfire no longer makes ematches to my knowledge due to litigation costs.

Chinese is widely available to explosives permit holders, as are mjg's. Generally speaking theyll run from 33 to 55 cents a piece. Also some are now shipping with fixed shrouds which cannot be removed (for safeties sake). Im not sure those would be ideal for rocketry.

Wow, I had no idea that ematches were considered explosives. That seems crazy since they have all of half a gram of "explosive" on the end. Thanks for all the info guys .

WillMarchant said:

Our club has a LEUP and we buy ready-to-go ematches from https://electricmatch.com/

I see he is now selling a dipping kit for hobby rocketry use...

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Any step needed to get a club LEUP? Is the club some form of business entity (e.g. LLC)? I assume one member must have the magazine storage, etc or do you have a storage facility where you fly?

Curious because it sounds like a good idea.

My friend and I have been using these since we have been using DD recovery, never had one fail. https://www.quickburst.net/q_match.htm

Nice! That's exactly what I am looking for, thanks.

rcktnut said:

My friend and I have been using these since we have been using DD recovery, never had one fail. https://www.quickburst.net/q_match.htm

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scatsob said:

Nice! That's exactly what I am looking for, thanks.

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Note that these have a fairly high all-fire current of 1A not the typical 300 to 400 mA. It's OK if you account for it (especially in clusted airstart applications and such). Personally I prefer a lower current match.

Sadly, these still require a permit. UN0454 is a 1.4s article pyrotechnic, and must be stored in a magazine.

The original thread:

https://www.rocketryforum.com/archive/index.php/t-1242.html

I'll still advocate people make their own. Cheap, easy, quick, and perfectly legal so long as you make them on site and use them the day you make them- which is very easy to do.

Kevin O

dixontj93060 said:

Note that these have a fairly high all-fire current of 1A not the typical 300 to 400 mA. It's OK if you account for it (especially in clusted airstart applications and such). Personally I prefer a lower current match.

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All-fire rating of Jteks is 0.7A with a no-fire rating of 0.3A. You really want a healthy no-fire rating for safety (especially with airstarts). 1A is really nothing, even a weak battery will source that. Wire the matches in series (as intended) and that single amp will easily fire 2-3 on a string.

All-fire ratings are conservative, the most standard definition is that the all-fire is the mean current +3.09 std.dev required to fire the match. For those with more interest on what all-fire and no-fire means here is a link.

https://neyersoftware.com/Papers/EandP99/ISO14304.htm

Industry practice is the ignition current should be 1.25X the all-fire rating.

jderimig said:

All-fire rating of Jteks is 0.7A with a no-fire rating of 0.3A. You really want a healthy no-fire rating for safety (especially with airstarts). 1A is really nothing, even a weak battery will source that. Wire the matches in series (as intended) and that single amp will easily fire 2-3 on a string.

All-fire ratings are conservative, the most standard definition is that the all-fire is the mean current +3.09 std.dev required to fire the match. For those with more interest on what all-fire and no-fire means here is a link.

https://neyersoftware.com/Papers/EandP99/ISO14304.htm

Industry practice is the ignition current should be 1.25X the all-fire rating.

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In series, though, would a single-cell Lipo have enough voltage to reach the all-fire current with just Ohm's law?

jderimig said:

All-fire rating of Jteks is 0.7A with a no-fire rating of 0.3A. You really want a healthy no-fire rating for safety (especially with airstarts). 1A is really nothing, even a weak battery will source that. Wire the matches in series (as intended) and that single amp will easily fire 2-3 on a string.

All-fire ratings are conservative, the most standard definition is that the all-fire is the mean current +3.09 std.dev required to fire the match. For those with more interest on what all-fire and no-fire means here is a link.

https://neyersoftware.com/Papers/EandP99/ISO14304.htm

Industry practice is the ignition current should be 1.25X the all-fire rating.

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No way! John I know you know a lot about altimeters, but as being originally a practicing EE, I have to take exception to your recommendation. Wire three e-matches in series for a cluster configuration and you if you happen to have one fire early burning the nichrome and opening the circuit you then have one motor of the three lit--i.e., disaster. They should be wired in parallel.

Yes, I mis-typed, old Daveyfire and Oxral e-matches pretty much match what I make personally with all-fire between 400 and 500 mA and no-fire less than 200mA (see: https://www.info-central.org/?article=305).

Thanks, John. Very interesting. It's been a while since I dabbled in statistics, but that actually (mostly) made sense to me

Kevin

dixontj93060 said:

No way! John I know you know a lot about altimeters, but as being originally a practicing EE, I have to take exception to your recommendation. Wire three e-matches in series for a cluster configuration and you if you happen to have one fire early burning the nichrome and opening the circuit you then have one motor of the three lit--i.e., disaster. They should be wired in parallel.

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eMatches are usually wired in series. Wiring in series reduces the current requirement and makes the continuity test more repliable. They fire so quickly that there's little chance of "having one fire early."

See: https://www.pyromate.com/Basics-of-Electrical-Firing.htm

-- Roger

dixontj93060 said:

No way! John I know you know a lot about altimeters, but as being originally a practicing EE, I have to take exception to your recommendation. Wire three e-matches in series for a cluster configuration and you if you happen to have one fire early burning the nichrome and opening the circuit you then have one motor of the three lit--i.e., disaster. They should be wired in parallel.

Yes, I mis-typed, old Daveyfire and Oxral e-matches pretty much match what I make personally with all-fire between 400 and 500 mA and no-fire less than 200mA (see: https://www.info-central.org/?article=305).

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Apparently, the plasma from the ematch flame conducts well enough and long enough to set off the other ones in series. Or so I've read.

I'm going to agree ematches should almost always be wired in series. In a properly designed circuit they will fire correctly. Even if your voltage is marginal, careful matching of resistances will add a layer of insurance.

Just a couple weeks ago I popped 100 ematches in a single series circuit. Took a special firing system (300v capacitive discharge), but it worked fine.

Kevin

dixontj93060 said:

No way! John I know you know a lot about altimeters, but as being originally a practicing EE, I have to take exception to your recommendation.

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Its controversial I know but it is not my recommendation, it is an industry standard practice. Commercial ematches are designed to be series wired.

The primer pyrogen is very fast and temperature sensitive. It is designed to ignite well below the temperature where the bridge wire is even changing color much less burning through.

There is a upper spec limit on the time to ignite and a lower spec limit on the time to burn through the bridgewire. The chemistry and construction is designed so the distance between these two limits are many sigma's apart.

The other reason for acceptance of series wiring is to enable continuity checking of the entire string.

Car Vacs question is a good one. You want 1.25x the all fire current so 4 1.2ohm ematches in series would not be be good practice with single cell Lipo. Parallel circuit would be better but then you lose continuity check ability through the altimeter. Best practice would be a high voltage pyro circuit series connected commercial ematches.:wink:

Edit: Ematches in series is also easier on your output fets.

If anyone wants to play around, I wrote a little excel spreadsheet that will give a pretty good idea if a circuit will work. It's designed for pyro work, but the principles are the same.

https://back2bed.com/cr.xls

To use, simply enter the ematch and firing system parameters in the yellow boxes. For rocketry, enter a "Cable Length" of zero.

Kevin

CarVac said:

Apparently, the plasma from the ematch flame conducts well enough and long enough to set off the other ones in series. Or so I've read.

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So you are relying on the chaotic/random event of plasma production to overcome the bell curve variation in e-match firing currents? Does not even come close to meeting my standard for "best practice" in rocketry even though it is done in the fireworks anf pyrotechnic industry.

CarVac said:

Apparently, the plasma from the ematch flame conducts well enough and long enough to set off the other ones in series. Or so I've read.

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Which illustrates another 'hazard' or parallel wiring. If one match goes 'short' early the others get thier current reduced.

Series baby!

dixontj93060 said:

So you are relying on the chaotic/random event of plasma production to overcome the bell curve variation in e-match firing currents? Does not even come close to meeting my standard for "best practice" in rocketry even though it is done in the fireworks anf pyrotechnic industry.

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Tim, no read my post. Series connection relies on the design and empirical testing statistical proof that the ignition time distribution is many standard deviations before wire burn-though time distribution.

Edit: Of course if you do not have this design or can statistically prove it (like with DIY matches), then yes you must hook up parallel.

This is also standard practice in the blasting industry. Don't you think leaving unexploded charges around would be a concern in that industry? Series wiring is generally an "all or nothing" deal, which is exactly what you want in demolition and igniting rocket clusters.

jderimig said:

Tim, no read my post. Series connection relies on the design and empirical testing statistical proof that the ignition time distribution is many standard deviations before wire burn-though time distribution.

Edit: Of course if you do not have this design or can statistically prove it (like with DIY matches), then yes you must hook up parallel.

This is also standard practice in the blasting industry. Don't you think leaving unexploded charges around would be a concern in that industry? Series wiring is generally an "all or nothing" deal, which is exactly what you want in demolition and igniting rocket clusters.

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John, I didn't see your second post before I posted, sorry. And I haven't read the attachment yet (I'm driving--but that's another safety matter). I will read it. I do understand your statement on the burn deviation being contained by the wire burnout, but if so, then your other statement that series failure is all-or-nothing doesn't align. For it to be all-or-nothing wire burnout must be the predominant failure mode (vs delay or non-fire) and must occur before any e-match in the series fires.

dixontj93060 said:

For it to be all-or-nothing wire burnout must be the predominant failure mode (vs delay or non-fire) and must occur before any e-match in the series fires.

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Tim,

It appears that the primary failure mode is an open in the circuit, wiring fault, or an abnormally high resistance in the chain, both easily detectable with a series resistance measurement.

Secondary failure mode is a pyrogen that doesn't ignite because of coating quality control issues.

Premature wire burnout failure appears to be a rare event given the popularity of the method in professional pyrotechnics and blasting given what's at stake during those endeavors as compared to rocketry. Now I am sure that blasting devices are MUCH more robust than pyro ematches, but the prinicples and theory of operation is the same, I think....

jderimig said:

Tim,

It appears that the primary failure mode is an open in the circuit, wiring fault, or an abnormally high resistance in the chain, both easily detectable with a series resistance measurement.

Secondary failure mode is a pyrogen that doesn't ignite because of coating quality control issues.

Premature wire burnout failure appears to be a rare event given the popularity of the method in professional pyrotechnics and blasting given what's at stake during those endeavors as compared to rocketry. Now I am sure that blasting devices are MUCH more robust than pyro ematches, but the prinicples and theory of operation is the same, I think....

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OK, you are saying all-or-nothing before an event occurs. I understand. And the e-match characteristics being designed to fit a series application... Well you learn something new everyday--thanks.

In shooting fireworks shows professionally, the use of ematch is now mandatory according to updated nfpa regs. Ive shot dozens of ematch at a time wired in series with such reliability that its a no brainer. I cant say the same for parallel wiring of ematch. For cluster applications, the use of parallel wiring can result in a false positive continuity check. 2 matches of the three may be good, or even only one, and youll still register continuity. This to me is a far greater risk than the chance of a tested match not lighting in series.