Parallel or Series

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Conway Stevens

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Im curious how many have run 2 ematches on one output for a single charge in parallel or series? Ive always been told wire them in series. But have had others say the do it parallel. I was under the understanding parallel would potentially fry the output.
 

waltr

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What are you using as the "output"???
What is the "output" Current rating??
 

Conway Stevens

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Mine are my Altimeters RRC2L RRC3 and a Raven 4. but ive heard others wiith Altus metrum or Perfect flight
 

heada

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Current needed to fire an ematch, true ematch and not an igniter, is normally less than 1A.(way less) and most electronics can source 10A for 1 second so even the worst setup, you could fire 10 ematches in parallel without issue.
 

Conway Stevens

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Current needed to fire an ematch, true ematch and not an igniter, is normally less than 1A.(way less) and most electronics can source 10A for 1 second so even the worst setup, you could fire 10 ematches in parallel without issue.
Im confident it will fire 2 or 3 ematches on a single output as it takes virtually nothing to fire them for current. What are the chances that it kills/damages the altimeter if wired in parallel?
 

Bat-mite

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Depends on your battery, I can attest that MissileWorks alts can fire two ematches in series or parallel with a 9V battery, With a LiPo, YMMV.

I used to go series because I thought the alts couldn't deliver enough current to do parallel. But series is risky because if there is no continuity in the first match, then neither one will light. Parallel is the way to go if your battery can handle it.
 

Conway Stevens

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Depends on your battery, I can attest that MissileWorks alts can fire two ematches in series or parallel with a 9V battery, With a LiPo, YMMV.

I used to go series because I thought the alts couldn't deliver enough current to do parallel. But series is risky because if there is no continuity in the first match, then neither one will light. Parallel is the way to go if your battery can handle it.
Battery can easily handle it. 300 mah 2s lipo 30c
The question im curious is will it damage the altimeter if wired in parallel firing 2 matches on the same output channel?
 

Bat-mite

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Battery can easily handle it. 300 mah 2s lipo 30c
The question im curious is will it damage the altimeter if wired in parallel firing 2 matches on the same output channel?
Again, that is what I do. I have tested two in parallel with RRC2+, RRC3, Altus EasyMini, and StratologgerCF. No problems.
 

heada

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The mosfet on the raven can do 10A. Not sure about the Missleworks.

2 ematches in parallel will normally draw less than 1A. No worries.
 

AllDigital

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I think that putting them in series defeats the purpose of using two eMatches. I've had at least two matches fail this year where they lost continuity, but did not fire. If you have a faulty match that loses continuity in series then there is a high probability that the other match doesn't get enough current to fire, before the first match disconnects.
Also, I did a bunch of testing last year and found that commercial MJG eMatches fire consistently at around .5A (or under 1A), while the cheap "orangies" often take 2-3A and when they go cold they regain continuity. So, I don't use the cheap ones in my recovery, but I do use them to make igniters to use with 12V pad launch systems.
 

Conway Stevens

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I think that putting them in series defeats the purpose of using two eMatches. I've had at least two matches fail this year where they lost continuity, but did not fire. If you have a faulty match that loses continuity in series then there is a high probability that the other match doesn't get enough current to fire, before the first match disconnects.
Also, I did a bunch of testing last year and found that commercial MJG eMatches fire consistently at around .5A (or under 1A), while the cheap "orangies" often take 2-3A and when they go cold they regain continuity. So, I don't use the cheap ones in my recovery, but I do use them to make igniters to use with 12V pad launch systems.

I would agree with everything youve stated. I myself understood it to begin with but was part of discussion with others and they brought up series wiring.

I also do not use the cheap ematches. MjG is what i use all the time.
 

JoePfeiffer

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When I've run two ematches in parallel from a StratloggerCF using a 1S LiPo, I've gotten an overcurrent warning on next powerup, but it's continued to work.
 

icyclops

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Parallel…if the first doesn’t work then the second won’t either if done in series…..
 

Sandy H.

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It is common on industrial machinery for multiple E-Stops to be run in series. If one drops, the whole circuit is dead. I wouldn't want an e-match acting like an E-Stop. . .Honestly, I'd want the opposite, which is why I assume a lot of people suggest redundancy.

If you don't have redundant channels, make sure you've got good e-matches/batteries and rely on single systems, I'd think.

Sandy.
 

jderimig

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Series. That is how ematches are designed to be used. But you need 2.5v for ematch in a string.

Electrical engineers will say parallel from there training. Pyro and explosive industry professions use series wiring.

Search this forum on this subject for justification, I won't repeat the reasons for the 15th time in this thread.
 

Sandy H.

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Series. That is how ematches are designed to be used. But you need 2.5v for ematch in a string.

Electrical engineers will say parallel from there training. Pyro and explosive industry professions use series wiring.

Search this forum on this subject for justification, I won't repeat the reasons for the 15th time in this thread.
Fair enough. You have more experience than me and run an altimeter business, so I agree that you would know more.

After you posted a comment to search, I apparently didn't use the right terms, as I didn't find an answer as to why you should use e-matches in series.

I'm always willing to learn, so if you could post a link to a previous thread or search terms, I'd like to learn more.
 

RocketScientistAustralia

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Both series and parallel connection have problems.
To understand this you have to know ohms law. Volts= Amps x Resistance, V=IR.
John has given a generally correct answer. Lets look at why. To do this we need to have the specification of the specific ematches you are going to use. It's best to start with a specific example and work to a general answer.
Here's the spec for J-Tec Lead free matches( from Google)

Pyrotechnic: Proprietary, contains no lead, mercury, cadmium or chromium compounds.
Soldering: Bridgewire and lead wires attached using lead-free solder.
Average Bridgewire Resistance: 1.0 ohm (Std. Deviation = 0.09 ohm)
Average Chemical composition: 0.04 Grams
Firing Characteristics:
Maximum No-Fire Current
0.30 amp. (300 milliamp.)
Minimum All-Fire Current
0.75 amp. (750 milliamp.)
Recommended Minimum Firing Current 1.00 amp.
Recommended Nominal Firing Current
1.25 amp.
Maximum Test Current
0.04 amp. (40 milliamp.)
Minimum Firing Pulse
1 ms. @ 170 v.; 10 ms. @ 12 v.
Minimum All-Fire Energy
4 mj. (4 millijoules)
Heat of Explosion (HOE)
718 cal/gram
Impetus
400 J/g
Flame Temp.
3709 K
Gamma
1.184
Co-volume
6.491 inches cubed per pound mass
Sensitivity:
J-Tek electric matches are less sensitive to impact, friction and electrostatic discharge than most similar products on
the market. However, the user should still observe industry recommended precautions to prevent damage to match
head and accidental application of ignition stimuli to match head or lead wires.
Electric matches are supplied with a protective rubber shroud for the match head which should never be removed.
Thermal Stability: Explosives Regulatory Division in Canada have tested and passed the J-tek igniter head at 75C/167F
for 48 hours.
Test Definitions:
Maximum No-fire Current - The maximum electrical current that can be applied to the electric match bridge wire
for 30 seconds that will not fire the match head.
Minimum All-fire Current - The minimum electrical current that can be applied for 1/2 second, which will always
fire the match head.
Data was taken at 1.5 volts

So from the spec ******************************************************************
Recommended Nominal Firing Current=1.25 amp.
Data was taken at 1.5 volts
Average Bridgewire Resistance: 1.0 ohm (Std. Deviation = 0.09 ohm)
Minimum Firing Pulse 1 ms. @ 170 v.; 10 ms. @ 12 v.
************************************************************************************
Connecting in series requires more voltage to be available from the power supply at the match firing end. If the match is rated as requiring 1.5 volts (as the spec above)across it to guarantee initiation, a 3.7v lithium would fire 1 and MAY fire 2depending on the voltage drops across the system in series but from a specification view you could not guarantee it.
Series connected guarantees that if there is any failure none of the pyro will fire.
It's considered to be fail safe. If you had a cluster of 3 motors you would need to guarantee 3x1.5 volts =4.5 volts available at the end of the cable connected to the matches. 100metres of standard 24/0.2 figure 8 cable has a resistance of 9 ohms.
So we need 4.5v @ 1.25 amps cable is 9 ohms. V drop across cable is 9x 1.25=11.25v plus 4.5v for the pyro in series=15.75 volts that needs to be supplied from the firing end battery.
Looking at a parallel connection. 3 matches each requires 1.25 Amps=3.75 amps to be supplied to the pyro. @ 1.5V. Voltage drop on connecting cable= 3.75x9=33.75 volts........ wowsers....... plus the 1.5 volts across the pyro. 35.25Volts needed for your supply battery.
When you connect in parallel any pyro ematch failure will not generally prevent the others from initiating.

So if you're firing a cluster and wire in parallel, you might get 1,2 or 3 motors firing. There's an exciting day for you. But probably all will ignite. Ematches are very reliable. But you'll need a higher voltage available to guarantee ignition to the specification from the manufacturer. In series you'll need a lower voltage to guarantee initiation of the ematches. If ANY match fails, all fail. In general a quality ematch does not fail on it's own. There are usually other factors such as poor handling of the ematch. ( ALSO don't forget that just because your ematch has fired, it doesn't guarantee your motor will light. That's another story......)

NOW Lets move on to using this new found knowledge for ejection charges. Similar but slightly different scenario. Here, what you want is to GUARANTEE the ejection charge goes off. So you'll think you'll parallel up the charges and if a match fails you'll be good. WRONG. So lets series them, as above this does not really give you any additional redundancy. In fact what it gives you is an additional failure point.

Most electronic flight computers will current limit the output and they'll only pulse on for up to 1 sec max. Most are 1/10 sec.
FOR THIS REASON, you MUST follow the recommendation of the flight computer manufacturer. You MUST make sure that the ematch you are using is listed for that flight computer. If you want redundancy, use a second output from the FC if one is available(set to go off 1 sec later) or better still a second flight computer. You want to test the specific batch of ematches with your flight computers before the launch and treat them with respect and care. Pack carefully.

Test what you're going to do and DO WHAT YOU'VE TESTED.

That was long...... No wonder John's fed up repeating it.

Good luck, fly high.
Norm
 

jderimig

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Series or parallel decision using 2 ematches is not life or death. Either would be reasonably more reliable over a single ematch. It sometimes (always?) turns into a pedantic discussion. As Norm said ematches on second outputs if you can do it would be superior practice.

One of many reasons I like series connection is the continuity check feature of your FC is maintained. If you pass a series connection you have continuity in both matches. That's not the case with a parallel connection.
 

cerving

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Series: maintains continuity to altimeter (if one is bad, no continuity). If one ematch is open, the other one won't fire either. If one ematch is dead-shorted, the other one will still fire.

Parallel: If either one has continuity, you'll get a continuity reading. If one ematch is open, the other one will still fire. If one ematch is dead-shorted, the other one may or may not fire, depending on how much current is available to it.

Pick your poison... both have scenarios in which they won't fire. It is very rare for a chip-based ematch to be dead-shorted, however, and you can (and SHOULD) check the resistance before your put them in your charge wells, so my personal preference is parallel.

I have also seen cases in which the ematch tested "good" but it didn't light the pyrogen... neither series nor parallel connections are going to help you in that case. Hopefully you don't get two of them like that in the same charge well.
 

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WARNING! With the unannounced redesign of the Duracell 9V battery, it will only provide 2A so firing 2 ematches in parallel can be a problem. Energizer Ultimate Lithium WILL provide the current. Most Li-pos 180 mah or larger will provide plenty of current. Don't go too large or you will fry the altimeter output. 1st is the inside of the new Duracell instead of the 6 AAAA cells it used to have. All brands are like this now :mad: :( The other 2 are the Energizer lithium with 3 1/2 AA cells.
Duracell new 9V 1.jpg Energizer Li 2.jpg Energizer Li 4.jpg
J-Tek ematches require an ATFE license to purchase. However, the FireWire matches are ATFE approved and don't require a license. They have the same all fire and no fire currents as J-Teks. https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator
 
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RocketScientistAustralia

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The resistance deviation is +-0.2 for FireWire instead of +-0.09 for the J-Tek. This gives a possible 40% resistance variation instead of 18%. Probably not an issue but worth noting. And this is why the altimeter manufacturers should specify which matches they have tested on their systems. This gives everyone a starting point for what works.
The undocumented changes to battery construction are a pita. Well spotted.
 

Michael L

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WARNING! With the unannounced redesign of the Duracell 9V battery, it will only provide 2A so firing 2 ematches in parallel can be a problem. Energizer Ultimate Lithium WILL provide the current. Most Li-pos 180 mah or larger will provide plenty of current. Don't go too large or you will fry the altimeter output. 1st is the inside of the new Duracell instead of the 6 AAAA cells it used to have. All brands are like this now :mad: :( The other 2 are the Energizer lithium with 3 1/2 AA cells.
View attachment 483404 View attachment 483405 View attachment 483406
J-Tek ematches require an ATFE license to purchase. However, the FireWire matches are ATFE approved and don't require a license. They have the same all fire and no fire currents as J-Teks. https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator
This topic popped up right on time. I made a change to my LOC IV. I put the tracker / altimeter in the nose and a pair EasyMini's in the AV bay for redundant dual deployment.

I use 350Ah LiPo's, most of the time. I like having a lot of battery time available in case pad time extends out more than I expected. Admittedly 350Ah LiPo's are overkill. I put two in the battery box and when they plug into the power distribution board I have two parallel 350Ah LiPo's or 700Ah of capacity.

Like this. Each box feeds a board that connects to a pair of EasyMini's:


EasyMini side. Don't hate on the wiring. I'm not finished with build yet. Everything will tied down.



Unrelated but here's the tracker bay. Pay no attention to the mess. I'm sure that the camera phone had some sort of focus issue :rolleyes:

 

RocketScientistAustralia

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This topic popped up right on time. I made a change to my LOC IV. I put the tracker / altimeter in the nose and a pair EasyMini's in the AV bay for redundant dual deployment.

I use 350Ah LiPo's, most of the time. I like having a lot of battery time available in case pad time extends out more than I expected. Admittedly 350Ah LiPo's are overkill. I put two in the battery box and when they plug into the power distribution board I have two parallel 350Ah LiPo's or 700Ah of capacity.

Like this. Each box feeds a board that connects to a pair of EasyMini's:


EasyMini side. Don't hate on the wiring. I'm not finished with build yet. Everything will tied down.



Unrelated but here's the tracker bay. Pay no attention to the mess. I'm sure that the camera phone had some sort of focus issue :rolleyes:

Perfect workshop. No wasted bench space and everything at your fingertips.... :) Did you add the rubber duckie to the Telemetrum yourself?
 

cerving

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LOL, that looks like my workbench... clear off just enough space at a time to do what you need to do. :)
 

Michael L

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Perfect workshop. No wasted bench space and everything at your fingertips.... :) Did you add the rubber duckie to the Telemetrum yourself?
That's my bench here in NM. My real pride and joy workbench is back in TX. I can work with 0204 components there because I have a microscope. I don't LIKE to work with them. I think they are vile, evil little spawns of satan :)

I did add the connector myself. It's not too hard to add it but you have to use an RP-SMA edge mount RF rated 50Ω connector. RP - reverse polarity, Ie it has a male pin in the center. At least for the antenna that I used it did.

NM Bench. The parts boxes on the right near my HP calculator stack (the only real calculator) is for a 1W guitar amp kit whose build was suspended by my need to rebuild the AV bay for dual deploy, there's at least one unbuilt QRP Labs kit in front of the high voltage DC supply and electronic load, my Sencore PR57 (fancy isolation transformer for powering tube circuits that have a PSU built in, and a pair of DC supplies on top of that. There's couple of audio generators, a Super Volt Ohmyst VTVM... and who knows what else under that mess


Texas Bench (I linked some of the equipment so that they had pretty faces for the photo :D ). All but the Weller is still installed there. I couldn't make myself buy that twice. The microscope is in another room with it's own soldering station and hot air station. Under the bench I have "stuff" for developing film :) Unfortunately the lit up Tek scope with the sine wave is in dire need of restoration, If my HP gear starts to go I'm not sure what I'll do about that. At some level test equipment is beyond my skills. If it's got tubes in it, generally speaking, I can deal with it.




LOL, that looks like my workbench... clear off just enough space at a time to do what you need to do. :)
Exactly!
 

OverTheTop

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Amen with that on the 0402 components brother. 0603 I can get target condition on the joints more often than not. 0402 are just a PITA. Target condition only about 20% of the time, if I'm lucky.
 

Mike Haberer

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I use 350Ah LiPo's, most of the time. I like having a lot of battery time available in case pad time extends out more than I expected. Admittedly 350Ah LiPo's are overkill. I put two in the battery box and when they plug into the power distribution board I have two parallel 350Ah LiPo's or 700Ah of capacity.

I like the power interface boards. What is your source?
 

cerving

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Amen with that on the 0402 components brother. 0603 I can get target condition on the joints more often than not. 0402 are just a PITA. Target condition only about 20% of the time, if I'm lucky.
0603's are just about the limit to what humans can hand-solder, IMHO 0402's require reflowing in an oven. That's why the smallest parts we use are 0805's... but we prefer 1206's because you can almost solder them without magnification (unless you're an old guy with crappy eyes like me).
 
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