What Ematches do you use ?? ?

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snowman2 said:
The ARTS 1 and 2 are different. The ARTS 2 has a current limiter to prevent brownout of the CPU. It won't reliably fire everything in the single battery mode. For example, when used with J-Tek ematches it should be used in the two battery configuration.
Click to expand...

This is a critical point! The NAR Safety Committee is reviewing a recent event in which a rocket lawn darted. It used an ARTS 2 in single battery configuration with J-Tek ematches.

The ARTS 2 in single battery mode fires at 0.5 amp for 0.25 second. The J-Tek has a no-fire current of .3 amp and an all-fire current of .75 amp (recommended current is 1.25 amps). This means that you could do a successful ground test (if you got "lucky" and picked a sensitive J-Tek) AND STILL FAIL in flight!

Please read the specs for all of the components in your system, AND do a ground test. And, for a bigger project, consider using dissimilar redundant systems.
 
Do QuickBurst's Hot Shot igniters qualify? If so, those were my "go to" igniters when I flew BP clusters, until the situation with the feds happened.:mad: Since then, I've had great success using Quest's Q2 igniters.
 
Warren said:
I have also had great success with xmas tree bulbs. Four dual deployment flights using the xmas bulb for both apogee deployment and main deployment; one of these flights was my successful level 2. I do remove the shorting wire at the base of the bulb. I use a long precision tweezer (Griot's Garage) to grab the wire and carefully unwrap it. In my experience the filaments are amazingly sturdy. Carefully packed with black powder and wadding, I do not worry about them shifting enough to break.

I like the idea of using two bulbs for redundancy. This makes great sense as the altimeter should have more than enough current to light up both filaments. Thanks -
Click to expand...

How long do the bulbs last? Do they need to be cleaned after each flight?

Thanks a lot,
Mike
 
sailmike said:
How long do the bulbs last? Do they need to be cleaned after each flight?
Click to expand...

The bulb part is open and the filament is used up each time. The socket is sometimes retained depending on the way the flyer setup their ejection system.
 
Ted C said: "This is a critical point! The NAR Safety Committee is reviewing a recent event in which a rocket lawn darted. It used an ARTS 2 in single battery configuration with J-Tek ematches.

The ARTS 2 in single battery mode fires at 0.5 amp for 0.25 second. The J-Tek has a no-fire current of .3 amp and an all-fire current of .75 amp (recommended current is 1.25 amps). This means that you could do a successful ground test (if you got "lucky" and picked a sensitive J-Tek) AND STILL FAIL in flight!"

Ted - what is the result of this review? Where can we see the report? What, if any, corrective action is recommended?

I find this a surprisingly unwise and flat-out scary design change IMHO.
To "save" the CPU from brown-out so it can "watch" itself auger in is a unique idea.
Seems like one of those ideas that sounded good in a power-point presentation but fell apart in implementation....

It would seem to me that firing the e-matches is job-one for the altimeter, why hold back?
I see only a few outcomes with high-current e-matches:
1 - The match needs to much current regardless -> auger in.
2 - You fire the drogue, but go brain dead -> Rapid, but non-ballistic descent.
3 - You fire the drogue and manage to ride through to try for the main. Yea!
4 - You hold back and "watch" the apogee and main events go by -> auger in.
Why is option #4 a good choice?

Is it done with the hope that the other pyro channels are filled with lower current matches?
How many people use more than one brand e-match on a flight?

Also, for a few pennies, you could isolate the CPU from the power rails sufficiently to ride thought the firing cycle.

I don't get it, but in any case it is another example where it pays to read the documentation and "use only as recommended."

Ted - please do tell us what NAR thinks and plans to do about this....
All my opinion,
FredA
 
freda said:
Ted C said:

Also, for a few pennies, you could isolate the CPU from the power rails sufficiently to ride thought the firing cycle.


FredA
Click to expand...


And for FREE, you can utilize the extensive brown-out detection and recovery features that are available in modern CPU's. -->Save state, brown-out, wake up from brown out restore state and keep on going.
 
freda said:
Ted - please do tell us what NAR thinks and plans to do about this....
Click to expand...

All of the information I quoted is available from the respective product user manuals. The way to avoid the situation is to use the altimeter as it was designed to be used--either use low current igniters in single battery mode, or use two batteries.

I'm trying to get the word out in the form of a reminder to read, understand, and follow manufacturer's instructions (with perhaps some emphasis on this particular case, given the increased popularity of these igniters) on the NAR list (and here! :) ); we also have a more general article on electronics use and safety being prepared for Sport Rocketry.
 
freda said:
Ted - please do tell us what NAR thinks and plans to do about this....
Click to expand...

Perhaps both organizations should commission articles to be published in their respective chosen magazines. One article could be about ematches. Many people think they are mysterious devices. Unfortunately many people also seem to think that all ematches have the same electrical characteristics, which is also not correct. Daveyfire used to make several types of ematches. My Daveyfire catalog lists 19 models. The N28B was probably the most popular.
 
freda said:
I find this a surprisingly unwise and flat-out scary design change IMHO.
To "save" the CPU from brown-out so it can "watch" itself auger in is a unique idea.
Seems like one of those ideas that sounded good in a power-point presentation but fell apart in implementation....
Click to expand...

The design changes from the ARTS to the ARTS2 are the results of our experiences over thousands of user flights. Every change either enhanced the product's safety or functionality. We thought this through very carefully and the implementation was excellent.

I cannot go through all of the changes and the thought processes behind them, but I will try to address those few brought up in this thread so that current and future Ozark customers can better understand the products.

freda said:
It would seem to me that firing the e-matches is job-one for the altimeter, why hold back?
I see only a few outcomes with high-current e-matches:
1 - The match needs to much current regardless -> auger in.
2 - You fire the drogue, but go brain dead -> Rapid, but non-ballistic descent.
3 - You fire the drogue and manage to ride through to try for the main. Yea!
4 - You hold back and "watch" the apogee and main events go by -> auger in.
Why is option #4 a good choice?
Click to expand...

Brown outs are problems that can have consequences much more serious than in your #2. After a brownout, the ARTS restarts it's program, but has no idea where it is, which way it is pointing, or how fast it is moving. If there are still live charges hooked up these could go off unexpectedly.

The only way #4 is going to happen is if the user ignores the recommendation to use separate batteries *and* ignores the clearly published current output specification. #4 will also happen if the user does not connect the charges to the ARTS! We cannot control the user! All we can do is to provide instructions and specifications, it is up to the user to follow them.

freda said:
I don't get it, but in any case it is another example where it pays to read the documentation and "use only as recommended."
Click to expand...
I'll take this a step further. These are High Power Rockets we are flying, where malfunctions could result in injury, property damage, and even death. Not reading the documentation and using the ARTS as recommended is CRIMINAL NEGLIGENCE.

Finally, if you believe that in your application the go-for-broke unlimited current option is best then fine! The ARTS2 can do that.

The ARTS2 can be configured in three ways:

1) Use two batteries. This should be your default option. Here battery #1 powers the CPU and battery #2 powers the pyro channels. The output current on the pyro-channels is not limited, it will use whatever current your battery #2 can provide. Note that sustained currents over 6 amps may damage the ARTS2.

2) Use one battery with current limiter. This option can be used when a second battery is impossible due to space or other constraints. With this option the output channel current is limited to 0.5A. Know the specs of your ematches and ground test!

3) Use one battery without current limiter. This option makes the ARTS2 behave exactly like the original ARTS in respect to the output current. The full current from the battery is available to the output channels. We do not recommend this option, because option 1 or option 2 are better for almost every situation. If you are certain that option 3 is best for your application you then you must be aware that CPU brownouts are possible and that a brownout may cause the ARTS2 to behave unpredictably.
 
Not reading the documentation and using the ARTS as recommended is CRIMINAL NEGLIGENCE.
Click to expand...

Says who?!?

Unless someone launches a rocket in such a way that is a "gross" deviation from what would be the standard safe protocols for launching a high power rocket, like launching from the back of a pick-up truck at a 45 degree angle toward a populated area, there are no grounds for criminal liability.

If someone use an ARTS altimeter incorrectly in a HPR rocket at an organized launch where proper safety protocols are followed and that individual is properly certified , and the rocket crashes and causes a serious accident, there are no grounds, whatsoever, for criminal liability, even if the altimeter was used in a way that deviates from documentation. The person may meet the tort standards for negligent behavior, but not for criminal negligence.

Now, if that same person launches a HPR rocket, from their backyard in the middle of a populated suburbs, and the rocket crashes and causes a house fire, then yes, that is grounds for criminal liability and perhaps even gross negligence depending on the actual situation.
 
Loki said:
Brown outs are problems that can have consequences much more serious than in your #2. After a brownout, the ARTS restarts it's program, but has no idea where it is, which way it is pointing, or how fast it is moving. If there are still live charges hooked up these could go off unexpectedly.
Click to expand...

Jeff with minor software changes you can deal with this situation. I am not sure what CPU you are using but most modern ones know if they are resetting from a brown-out. If it has commanded a apogee pyro event (which you can store in a NVM location, and the CPU resets from a brown-out, you know you are going down. You can them sample the baro sensor and decide what to do with the main pyro output.
 
jderimig said:
Jeff with minor software changes you can deal with this situation. I am not sure what CPU you are using but most modern ones know if they are resetting from a brown-out. If it has commanded a apogee pyro event (which you can store in a NVM location, and the CPU resets from a brown-out, you know you are going down. You can them sample the baro sensor and decide what to do with the main pyro output.
Click to expand...

Actually, its a much easier fix to do in hardware. The software fix would basically be a "bandaid" to a problem elsewhere without solving the original problem.

A simple filter on the power pin, designed with the proper time constant (i.e. 1-2 seconds) of the anticipated brown out from an electric match firing, etc... is all that is required. This would also protect from any glitches from a disconnect do to launch forces from the battery. Isolation could be achieved by using a series diode to prevent the filter from discharging back towards the battery. The load presented by the uproc quite small so the capacitor required would be relatively small.
 
Loki said:
We thought this through very carefully and the implementation was excellent....
Click to expand...

My earlier post was not intended to reflect on either the altimeter or the e-match in use at the time, but to once again point out that it is important to read and understand the product literature for all of the products you use.

Increasing regulatory pressures have reduced the availability of low-current igniters and e-matches. New products are certainly capable of doing the job, but flyers must READ and UNDERSTAND the current requirements for those products, and ensure that their electronics are configured to deliver the required current.

With respect to the original topic of this thread, your e-match selection MUST be in part determined by the altimeter you plan to use, and how you plan to use it.
 
Brownout can cause more serious problems???
Fire the darn ematches...period...job one!
IF you wake up from a brown out and are confused and fire the ematches, you probably did the best thing possible.

FIRE THE EMATCH!!!

None of this hold back and hope crap...what a load of BS....

The altimeter's job is to fire the e-match...nothing else.
Sure we would like it to fire perfectly at apogee, but no-fire is WRONG! DEAD WRONG!
Don't worry about left-over un-fired charges - I find they usually fire on IMPACT!
If that's you real worry, then I hope your documentation recommends double-throw switches to disable and shunt all charges during handling....a better way to "safe" the rocket before and after the flight.

So you didn't want to spend the money for a diode and capacitor....we understand, margins are low. But take out the stupid SW hack that "protects" the CPU from brown out....

Again - if the CPU can't fire the match, it DIES when the rocket augers in.
If the user forgets the second battery, or uses a high current ematch, try anyway!!!
How is your protection SW a wise choice...you've not explained that!


Is the altimeter designer who made this choice guilty of criminal negligence if somebody is hurt as a result????
 
freda said:
Brownout can cause more serious problems???
Fire the darn ematches...period...job one!
IF you wake up from a brown out and are confused and fire the ematches, you probably did the best thing possible.

FIRE THE EMATCH!!!

None of this hold back and hope crap...what a load of BS....

The altimeter's job is to fire the e-match...nothing else.
Sure we would like it to fire perfectly at apogee, but no-fire is WRONG! DEAD WRONG!
Don't worry about left-over un-fired charges - I find they usually fire on IMPACT!
If that's you real worry, then I hope your documentation recommends double-throw switches to disable and shunt all charges during handling....a better way to "safe" the rocket before and after the flight.

So you didn't want to spend the money for a diode and capacitor....we understand, margins are low. But take out the stupid SW hack that "protects" the CPU from brown out....

Again - if the CPU can't fire the match, it DIES when the rocket augers in.
If the user forgets the second battery, or uses a high current ematch, try anyway!!!
How is your protection SW a wise choice...you've not explained that!


Is the altimeter designer who made this choice guilty of criminal negligence if somebody is hurt as a result????
Click to expand...

Wow. The IQ points are flying on this one. And this guy is a TAP member?
This is a perfect example of the classic "brain fart."

I hate to be the poor lad who is turning on his altimeter at the pad getting ready for launch . . .:(
 
I have used Oxrals for many years (mfg plant is only 20 miles from where I live), but now that I am out, I have been using Cosmos matches from Quickburst. When those run out, I will implement the Hotcoils from Quickburst that I purchased along with my HA45 altimeter.

Johnnie
 
jderimig said:
Jeff with minor software changes you can deal with this situation. I am not sure what CPU you are using but most modern ones know if they are resetting from a brown-out. If it has commanded a apogee pyro event (which you can store in a NVM location, and the CPU resets from a brown-out, you know you are going down. You can them sample the baro sensor and decide what to do with the main pyro output.
Click to expand...

John, thanks for the helpful suggestion. I'll ask Erik Hall (the ARTS designer and programmer) about this. I don't know if the ARTS's CPU has such a feature.
 
eastvolt said:
Says who?!?

Unless someone launches a rocket in such a way that is a "gross" deviation from what would be the standard safe protocols for launching a high power rocket, like launching from the back of a pick-up truck at a 45 degree angle toward a populated area, there are no grounds for criminal liability.

If someone use an ARTS altimeter incorrectly in a HPR rocket at an organized launch where proper safety protocols are followed and that individual is properly certified , and the rocket crashes and causes a serious accident, there are no grounds, whatsoever, for criminal liability, even if the altimeter was used in a way that deviates from documentation. The person may meet the tort standards for negligent behavior, but not for criminal negligence.

Now, if that same person launches a HPR rocket, from their backyard in the middle of a populated suburbs, and the rocket crashes and causes a house fire, then yes, that is grounds for criminal liability and perhaps even gross negligence depending on the actual situation.
Click to expand...

Okay, I'm not a lawyer and perhaps I used the wrong terms to express my feelings. I hope my point was clear. High Power Rockets have the potential to do serious harm. The recommendations of the manufactures for the critical components of these rockets should not be taken lightly as the misuse of these products could have terrible consequences.
 
freda said:
Brownout can cause more serious problems???
Fire the darn ematches...period...job one!
IF you wake up from a brown out and are confused and fire the ematches, you probably did the best thing possible.

FIRE THE EMATCH!!!

None of this hold back and hope crap...what a load of BS....

The altimeter's job is to fire the e-match...nothing else.
Sure we would like it to fire perfectly at apogee, but no-fire is WRONG! DEAD WRONG!
Don't worry about left-over un-fired charges - I find they usually fire on IMPACT!
If that's you real worry, then I hope your documentation recommends double-throw switches to disable and shunt all charges during handling....a better way to "safe" the rocket before and after the flight.

So you didn't want to spend the money for a diode and capacitor....we understand, margins are low. But take out the stupid SW hack that "protects" the CPU from brown out....

Again - if the CPU can't fire the match, it DIES when the rocket augers in.
If the user forgets the second battery, or uses a high current ematch, try anyway!!!
How is your protection SW a wise choice...you've not explained that!


Is the altimeter designer who made this choice guilty of criminal negligence if somebody is hurt as a result????
Click to expand...


I don't know why Fred is shouting at me and calling BS, when I am basically agreeing with him. Firing an apogee deployment charge is the most important thing. Everything we have done with the ARTS2 has been to ensure this happens. But also keep in mind that the ARTS2 is very flexible device and is often used for duty other than standard apogee-main deployment. Users can and have used the outputs to do all sorts of things besides firing ematches.

I said this before and I'll repeat it here: The ARTS2 offers three options:

#1 (Fred's way) Take all available juice from the only battery and dump it to the output. As long as the battery can supply enough current, everything is fine. The ARTS2 does have some hardware brownout protection, but if the battery voltage drops too low for too long the CPU will reset.

#2 Add a second battery. Now we can send all available juice from a completely different source to the ematch. If we overload this second source, the CPU is not at risk.

#3 Use a single battery, but limit the current available to the outputs. Obviously, if you choose this option you had better be sure that the available current is enough to get the job done, whatever that job may be. Operating a relay? Using ematches that fire to a shorted condition? Running the ARTS2 on a 23A battery? This might be the correct choice for you.

I don't see how having more options is bad. If one of these options doesn't fit your purpose, then use one of the others.

Robert Briody wrote up a very good report on the current requirements of some of the available ematches and ignitors. Here's the link. I suggest that anyone using electronics for parachute deployment should give this a read.
 
Loki said:
...
#1 (Fred's way) Take all available juice from the only battery and dump it to the output. As long as the battery can supply enough current, everything is fine.
...
Click to expand...

I don't find that described in the manual, Jeff.
 
Loki said:
Okay, I'm not a lawyer and perhaps I used the wrong terms to express my feelings. I hope my point was clear. High Power Rockets have the potential to do serious harm. The recommendations of the manufactures for the critical components of these rockets should not be taken lightly as the misuse of these products could have terrible consequences.
Click to expand...

I agree 100%.
 
Robert Briody wrote up a very good report on the current requirements of some of the available ematches and ignitors. Here's the link. I suggest that anyone using electronics for parachute deployment should give this a read.
Click to expand...

Robert's report is not really a report on what the current requirements are for igniters. The report deals more with what effect igniters have on the batteries being used to ignite them - in particular a 9V battery using an altimeter that doesn't current limit its output and how much voltage drop you get internally in the battery when high peak currents are present.
 
WillMarchant said:
I don't find that described in the manual, Jeff.
Click to expand...

I don't think it's on the quick start card, but it should be in the .pdf manual.

Anyway, it's easy to set up. Leave the jumper on the ARTS2 board off (as is normal for a two battery set up). Then connect your single battery to both the CPU and the Pyro battery terminals.
 
eastvolt said:
Robert's report is not really a report on what the current requirements are for igniters........
Click to expand...

The report is well done and exactly on topic. I won't characterize it further, lest you find some other detail to quibble over.
 
Loki said:
The report is well done and exactly on topic. I won't characterize it further, lest you find some other detail to quibble over.
Click to expand...

Sorry, don't agree with this at all. Both the methodology used to characterize the igniters is flawed and the conclusion is equally as flawed.

What the author does in this case is hook up a 12V lead acid battery to an igniter and record what the current waveform looks like and then attempts to compare this current to the manufacturers specifications. Whats wrong with this? Well, current is a function of the voltage and impedance of the source and load. Obviously, as you increase voltage, the peak current will be higher, and as you decrease voltage, the peak current will be lower.

What the author fails to realize is that whats important here is the area underneath the current waveform. Basically, the current waveform integrated with respect to time. This will tell you just how much "heat" is created and is required to fire an igniter. I didn't look at the waveforms in detail, but i imagine if you compared both the author's measured waveforms with the manufacturers spec (which do show current * time), they would be quite similar.



The collected data is valid, but the analysis and conclusions based on the measured data is not correct.
 
I believe eastvolt is correct. The study shows how much current an ematch can draw, which is fine for helping figure out if an altimeter using that same power source will stay alive or not.

But it doesn't say how much current it takes to fire the igniter in the first place. It may take far less current to heat up an ematch until the pyrogen starts burning than the ematch will actually draw from an unregulated power supply.

The way to do this test is to put the ematches on a current-limited power supply for a fixed period of time, and ramp up the current over several trials until the match fires. Repeat for several samples, take an average and a standard deviation. That tells you, with a known confidence, how much the match needs to fire.
 
Loki said:
Okay, I'm not a lawyer and perhaps I used the wrong terms to express my feelings. I hope my point was clear. High Power Rockets have the potential to do serious harm. The recommendations of the manufactures for the critical components of these rockets should not be taken lightly as the misuse of these products could have terrible consequences.
Click to expand...

Jeff

In this legalese society I'm more inclined to follow your lead. If, after the manufacturer makes a statement as such " Not reading the documentation and using the ARTS as recommended is CRIMINAL NEGLIGENCE." and one skewers someone at a launch due to ignorance of a device and it's disovered in a public thread they have said "Says who?!?", I'm figuring the skewered (should they live) will have the wages of one "says who?" attached for life.

Ignorance is no excuse when causing bodily harm. Should one "says who?" harm my son I will, and I swear, I will own him.

His attitude is a very wreckless attitude and should cause no need for a Loki apology. We will keep this thread on file since this guy is nearby.

Chuck
 
Ted Cochran said:
The way to do this test is to put the ematches on a current-limited power supply for a fixed period of time, and ramp up the current over several trials until the match fires. Repeat for several samples, take an average and a standard deviation. That tells you, with a known confidence, how much the match needs to fire.
Click to expand...

This will produce the wrong result for the simple reason that a test at a current too low to activate an e-match can heat it sufficiently to alter the properties of the bridgewire or pyrotechnic compound. The correct approach is a Bruceton test or one of its successors.

Each article under test must be tested once and then discarded no matter what happens. Needless to say this can consume a lot of test articles. Which is why a lot of thought has been expended on this subject. It is what is known as a sensitivity test and occurs in other fields as well.

The all-fire current is the average plus three sigma.
 

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