StratologgerCF

[Steven88]

Hello. I have purchased the StratoLoggerCF Perfect Flight altimeter for my first dual deploy rocket. The manual suggests using at least two ematches for the main and two for the drogue for redundancy. Really? Do most guys double up on their ematches like that for added insurance? I am using a standard 9v battery. When I ground test my ebay using four ematches (two for drogue and two for main), it fires all four ematches succesfully. However, upon turning my altimeter on again the next time following the test, it gives me error code #2 which means, taken from the manual: The battery voltage to the altimeter dropped briefly to less than 50% of its initial voltage at some point during the flight. The altimeter’s brownout protection allowed the altimeter to continue normal operation, but a loose connection or other issue is likely. Inspecting the downloaded voltage data will aid in diagnosing the underlying cause... I have not purchased the cable to be able to hook the altimeter up to my pc and diagnose the problem so that is not an option for me. Do you think that four ematches is just pulling too much juice for my 9v battery or do I have another problem? It does not throw the code with using only two ematches. Maybe this is something I should contact Stratologger about instead? Thanks in advance for the advice

 

[DaveW6DPS]

They do recommend using two in parallel, but in the paragraph before caution to not exceed the current limit of 5 amps. You need low current e-matches to be sure. Make sure the e-matches each draws 2 amps or less if you parallel them from a StratologgerCF.

Were you using the recommended MTek or JTek e-matches?

I have not doubled the e-matches any time I have used a Stratologger, or any other altimeter. Real redundancy is using a complete second altimeter. Don't get me started on heterogeneity and common mode failures...

It is usually a good idea to contact the manufacturer, also.

I do recommend the data cable. For about $25 you can download a lot of data about your flights. Not required, but it does increase your credibility a true rocket nerd.​

 

[Steven88]

No, I could not find the JTek or MTek ematches online and the China ones I have are low current so was hoping they’d work ok.

 

[SparkyVT]

I will second Dave's suggestion. I only run a single match for each output. Using commercial e-matches, I find them highly reliable with only a handful of failures in over 400 HPR flights. Like Dave suggested, I have redundancy through a second altimeter. That saved me today when I forgot to check the voltage of my stratologger battery. I dropped below 7V and I didn't catch it pre-flight. The battery failed when the stratologger tried to fire the apogee event, but the backup altimeter saved a 32lb rocket from coming in ballistic from 7500ft. Big rockets need a backup.

Chris Short sells the J-tek ones that are permit-free on his website: www.csrocketry.com. Its worth a look.

 

[Rex R]

what brand battery are you using? are you using a voltmeter to measure battery voltage before flight?
Rex

 

[Steven88]

I’m using a brand new Duracell battery for my altimeter. No, I didn’t check it with a voltmeter but I did listen to the altimeter beep prompts when I turned the altimeter on and it says it had 8.5V

 

[Steven88]

I will second Dave's suggestion. I only run a single match for each output. Using commercial e-matches, I find them highly reliable with only a handful of failures in over 400 HPR flights. Like Dave suggested, I have redundancy through a second altimeter. That saved me today when I forgot to check the voltage of my stratologger battery. I dropped below 7V and I didn't catch it pre-flight. The battery failed when the stratologger tried to fire the apogee event, but the backup altimeter saved a 32lb rocket from coming in ballistic from 7500ft. Big rockets need a backup.

Chris Short sells the J-tek ones that are permit-free on his website: www.csrocketry.com. Its worth a look.

 

[Steven88]

I understand two altimeters on a rocket the size and weight of yours, but mine is the Madcow Torrent with paper tubes. I have lengthened it and added larger parachutes, brass shim shear plates, extra centering ring and used epoxy on almost the entire build. Instead of coming in at 4 lbs it’s gonna nearly top 6 or more lbs. would you suggest two altimeter for a build such as this? Thanks again

 

[cwbullet]

I have build quite a few rocket this size. I build my 4 inch rocket with the ability to take 2 altimeters, but often fly them with just one. 6 inch and larger, I always put in redundancy. If it 100% needed, no, but it make me feel better.

 

[Buckeye]

Don't over-complicate your first dual deploy with two altimeters. Sources of error in hobby dual deploy:

1. Human
2. (rare) commercial ematches
3. (extremely rare) altimeter

Get the data cable and use it to learn, diagnose, and ground test the hell out of your altimeter and ejection charges. Then you will be confident in your setup

 

[cwbullet]

Don't over-complicate your first dual deploy with two altimeters. Sources of error in hobby dual deploy:

1. Human
2. (rare) commercial ematches
3. (extremely rare) altimeter

Get the data cable and use it to learn, diagnose, and ground test the hell out of your altimeter and ejection charges. Then you will be confident in your setup

Dual deploy is redundancy and it is not over complicating unless you are doing something different than I am. I have never seen an error with redundancy when it is done with the KISS method. I have seen plenty of mistake trying to cut corners. My redundancy is have two separate circuits, charges, and altimeters.

We use redundancy in medicine to prevent mistakes from making it to the patient. The same is true for rocketry. Having a second circuit to back up the first is a good thing in some instances. Heck, NASA has multiple redundancies for most circuits. The military does the same thing.

I use redundant altimeters in all of my big rockets. I use the normal size charge for the first deployment and make the second just a bit larger. I set the main to go off at 1000 with the back up at say 700. I have had both charges go off most of the time. When only one goes off, I am glad I had a back up. Failures happen but two failures rarely happen.

You can ask 10 people and get ten answers. Do what you feel comfortable with.

 

[Rex R]

fresh out the package battery should be upwards of 9.6v, 8.5v is time for a new battery.
Rex

 

[Zeus-cat]

Rex makes a great point, a new battery should be over 9 volts. 8.5 volts is to low to be used in a rocket.

Are you using motor deployment as a backup? I highly recommend it if your motor delay is longer than your expected time to apogee. Apogee deployment is far more important than main deployment. If you fail to separate your rocket at apogee you WILL have a serious problem unless you are very lucky. If you separate at apogee, but fail to deploy your main, you will likely have just a minor problem that can easily be repaired.

 

[SparkyVT]

I agree with Buckeye. Don't over complicate. With your rocket, running a single e-match per event with a single altimeter is perfectly fine and you'll end up with a perfectly safe flight 99.99% of the time. Motor ejection for backup is also a great idea. Getting the cable is very helpful to diagnose issues. That's how I figured out my voltage problem post-flight. Ground testing is also a good idea, but just be careful.

 

[cwbullet]

I agree with Buckeye. Don't over complicate. With your rocket, running a single e-match per event with a single altimeter is perfectly fine and you'll end up with a perfectly safe flight 99.99% of the time. Motor ejection for backup is also a great idea. Getting the cable is very helpful to diagnose issues. That's how I figured out my voltage problem post-flight. Ground testing is also a good idea, but just be careful.

Explain to me what is complicated about 2 separate redundant altimeters? Safety is number one. Redundancy builds safety not complexity. I do have th throw out the flag. I have yet to meet anyone who has 99.99% success rate. If you say you do, I think you are exaggerating. That is a 999 out of 1000 flight success rate. No one is that level success outside of maybe the airlines. Then again, they have redundancy. Having more than one flight computer increases success, not reduces it.

 

[cwbullet]

No, I could not find the JTek or MTek ematches online and the China ones I have are low current so was hoping they’d work ok.

China matches work fine.

 

[Steven88]

appreciate the help, everyone. I just tried another fresh 9V battery out of the same pacakage and this one comes in at 9.5v. I must have had a bad battery?

 

[SparkyVT]

Good call Chuck. Its not complicated, he just has a smaller, lighter rocket. One altimeter with one e-match per output is perfectly fine.

Sorry, I re-read my post and it can be misleading. If using commercial ematches and a properly powered stratologger, the odds are very low that the combination of the two will fail. Failures occur at higher rates, but will most likely be attributed to something other than the e-match / altimeter combination.

Here are the numbers out of my personal database:

455 High Power dual-deploy flights over 13 years
1080 e-matches used on those flights
Of those, I've had a total of 4 e-match failures (2 of which I suspect were due to a loose connection)
I have seen zero failures attributable to the altimeters (mostly Perfectflite)

Thus, my observed failure rate for a Perfectflite altimeter and commercial e-match combination is between 0.37% and 0.185% depending on how you count

My overall failure rate is much higher at about 15%, but due to things like stuck chutes, motor CATOs, dead batteries, etc.

 

[Steven88]

Rex makes a great point, a new battery should be over 9 volts. 8.5 volts is to low to be used in a rocket.

Are you using motor deployment as a backup? I highly recommend it if your motor delay is longer than your expected time to apogee. Apogee deployment is far more important than main deployment. If you fail to separate your rocket at apogee you WILL have a serious problem unless you are very lucky. If you separate at apogee, but fail to deploy your main, you will likely have just a minor problem that can easily be repaired.

 

[Steven88]

Rex makes a great point, a new battery should be over 9 volts. 8.5 volts is to low to be used in a rocket.

Are you using motor deployment as a backup? I highly recommend it if your motor delay is longer than your expected time to apogee. Apogee deployment is far more important than main deployment. If you fail to separate your rocket at apogee you WILL have a serious problem unless you are very lucky. If you separate at apogee, but fail to deploy your main, you will likely have just a minor problem that can easily be repaired.

Yes, I will be using motor backup for the drogue.

 

[DaveW6DPS]

Yes, I will be using motor backup for the drogue.

Motor back-up and single e-match per channel is a very normal, and normally successful, method of recovery. If your altimeter tests good with one of your e-matches and bad with two, go with one.

I use a new battery for each flight. They typically cost less than an e-match, and far less than a motor. Just plan on them being disposable, and use them for other stuff after a launch. I have enough other things that use 9V batteries that it isn't a waste. Safe recovery is worth a couple of dollars.

I still test each battery with voltmeter shunted by 20 ohms to verify. Just a voltmeter, or the altimeter voltage measurement can be misleading.

 

[The Geoff]

A simple question on electronics and redundancy. Years back I flew RC aircraft and I remember a device that would connect between the battery and the devices to essentially load balance for multi engines. Can't remember the name of the component but would something like this be of use in light of the complexity of some of the electronics in today's rockets; altimeters, trackers, cameras and flight computers.

I am just starting to plan my L2 cert, but don't want to over think the issue.

 

[JDcluster]

No, I could not find the JTek or MTek ematches online and the China ones I have are low current so was hoping they’d work ok.

They are there:
https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator

 

[Bat-mite]

Explain to me what is complicated about 2 separate redundant altimeters? Safety is number one. Redundancy builds safety not complexity. I do have th throw out the flag. I have yet to meet anyone who has 99.99% success rate. If you say you do, I think you are exaggerating. That is a 999 out of 1000 flight success rate. No one is that level success outside of maybe the airlines. Then again, they have redundancy. Having more than one flight computer increases success, not reduces it.

Actually, that's 9999 out of 10,000 flights. I'll go under my rock now.

 

[cwbullet]

Actually, that's 9999 out of 10,000 flights. I'll go under my rock now.

Good point. I was a sticker and I had it wrong.

 

[Jmhepworth]

Never do math in public.

 

[blackjack2564]

I have been using 2 matches on Stratologgers for years now. Never failed. 2 in parallel.
When flying rockets that don't have space for 2 altimeters I use 2 matches on each event.
This works for me with Adept-Stratto-RRC3-telemega-Pet-2 timers etc. every type of electronic I have used.
9 volt & Lipo's 3.7 and 7.4

 

[cavecentral]

I have been using 2 matches on Stratologgers for years now. Never failed. 2 in parallel.
When flying rockets that don't have space for 2 altimeters I use 2 matches on each event.
This works for me with Adept-Stratto-RRC3-telemega-Pet-2 timers etc. every type of electronic I have used.
9 volt & Lipo's 3.7 and 7.4

I thought about 2 ematches per charge from 1 altimeter. I only use perfect flight altimeters. Strattologger or cf version i tested on the ground. I always had 1 light, but never both. So, I scrapped the idea. I was using a 9v battery in the tests. I believe a capacitor fires the charges, but not 100% certain.

A buddy tried it without testing and had a failure. I shared my results with him earlier, so he didn't try 2 again.

It is possible 1 fired and lit the other, so ground testing may be on order. I think these were the chinese ematches. I did fire the other stand alone to make sure it was not a dud.

 

[Buckeye]

I thought about 2 ematches per charge from 1 altimeter. I only use perfect flight altimeters. Strattologger or cf version i tested on the ground. I always had 1 light, but never both. So, I scrapped the idea. I was using a 9v battery in the tests. I believe a capacitor fires the charges, but not 100% certain.

A buddy tried it without testing and had a failure. I shared my results with him earlier, so he didn't try 2 again.

It is possible 1 fired and lit the other, so ground testing may be on order. I think these were the chinese ematches. I did fire the other stand alone to make sure it was not a dud.

Not sure what is going wrong for you, but Perfectflite altimeters and all the ones CJ mentioned will easily fire 2 ematches per event. Parallel or serial, your choice.

 

[cavecentral]

Not sure what is going wrong for you, but Perfectflite altimeters and all the ones CJ mentioned will easily fire 2 ematches per event. Parallel or serial, your choice.

Yeah, that part is a mystery. I would have thought there was plenty of power too. I think I did try both parallel and serial. I was testing with the armed ebay and just the ematches. Using a straw to change the air pressure in the sealed ebay to make the match fire.

I am using JST connectors to the lids and have a terminal block for the ematch. Possible adding too many connections increasing overall resistance. Still, didn't think it would be an issue.