Author Topic: EEVblog #339 - Cypres Parachute Teardown  (Read 15552 times)

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Offline mgregg

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EEVblog #339 - Cypres Parachute Teardown
« on: August 22, 2012, 08:17:42 am »
First off, I just joined the forums here, so I hope I am posting in the correct place.

The cypress AAD teardown today was great!

I am a skydiver and I own some cypress AAD's. All of mine are the newer "cypress 2" model. I suspect that the internals of those are less old school.

For those that do not know what AAD stands for, it stands for "Automatic activation device"

The cypress aad that was in the teardown today was first released in 1992, and the construction of that device does appear to be indicative of a design from the early 1990's.

Anyhow, thanks David for the teardown, thanks Steven for sending in your AAD.

I'll ship in my cypress 2 when it times out in a few more years.
 

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #1 on: August 22, 2012, 09:04:48 am »


Dave.
 

Offline mikeselectricstuff

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #2 on: August 22, 2012, 09:57:21 am »
I wonder if the cap in the battery was due to them finding the battery couldn't give enough power to fire at low temperatures, or they were worried about electrolytic lifetime, so it gets replaced when the battery is changed....

When are you going to try firing the pyro..? I think it should be attatched to a rope from which a large anvil is suspended, with a pile of crappy multimeters below.

 
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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #3 on: August 22, 2012, 10:11:19 am »
I wonder if the cap in the battery was due to them finding the battery couldn't give enough power to fire at low temperatures, or they were worried about electrolytic lifetime, so it gets replaced when the battery is changed....

When are you going to try firing the pyro..? I think it should be attatched to a rope from which a large anvil is suspended, with a pile of crappy multimeters below.

I had exactly that idea!
I don't have an anvil though unfortunately.
I need to bring some gear home to do it, don't want to do it in the lab lest there is any loud noise, or smoke that sets off the buildings fire alarm!

I've used almost identical sized lithium primary batteries in a military design that had to work down to low temps and there were no issues with driving a high current heater element.
Yes, maybe worried about lifetime, although I'm not sure what advantage there is to having the cap across the battery that far from the circuitry.

Dave.
 

Offline N2IXK

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #4 on: August 22, 2012, 10:47:08 am »
Great teardown!

I think the pressure sensor must be an absolute type, not gage. Gage type measures the applied pressure relative to ambient? atmosphere. When you WANT to measure the ambient atmospheric pressure (like an altimeter would), you need an absolute type sensor, which are available with either a vacuum reference or a standard 1 atm. reference (commonly used for barometers).

Any idea on what the RTC does for a living? Disables the device after a preset "expiration date"? Log date/time of any deployments for investigators to use?
« Last Edit: August 22, 2012, 10:50:04 am by N2IXK »
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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #5 on: August 22, 2012, 11:04:46 am »
I think the pressure sensor must be an absolute type, not gage. Gage type measures the applied pressure relative to ambient? atmosphere. When you WANT to measure the ambient atmospheric pressure (like an altimeter would), you need an absolute type sensor, which are available with either a vacuum reference or a standard 1 atm. reference (commonly used for barometers).

Yes, it would be either the "sealed" gage type, or a vacuum type. Terminology can get mixed up sometimes.
I just don't get how they can get the accuracy though.
Sure, you switch the thing on on the ground and it can take the reference level.. But then what if the either the ambient pressure level changes by the time you jump and/or you your landing point is higher than your reference point?

Quote
Any idea on what the RTC does for a living? Disables the device after a preset "expiration date"? Log date/time of any deployments for investigators to use?

Most likely does some data logging for investigation. But there is no non-volatile memory, so you'd have to rely on the battery staying connected after the splat.

Dave.
 

Offline Chasm

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #6 on: August 22, 2012, 11:07:11 am »
It is an absolute gauge, the reference value is set when you press the button.

And yes, you must set a new reference height when you change heights, say jumping from different airfields. RTFM or die. ;)
(And yes, occasionally someone dies because of that. One rather high profile case was an German politician. Did not set the reference, did not pull the chute, did not go to prison for tax evasion and other assorted crimes.)
 

Offline poptones

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #7 on: August 22, 2012, 11:41:41 am »
Don't you think the sensor is the reason for the goopy jelly? That way the device can be completely sealed, but the goop deforms enough to allow the baro sensor to work. Ford autos back in the 80s had this exact same setup in their MAP sensors - sometimes they'd fail and when you'd pull off the vacuum line the potting compound would have evacuated into the hose.
 

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #8 on: August 22, 2012, 11:49:00 am »
Don't you think the sensor is the reason for the goopy jelly? That way the device can be completely sealed, but the goop deforms enough to allow the baro sensor to work.

I don't think so. The potting compound is to protect the electronics from moisture ingress. The sensor would have a sealed reference level, the offset of which the user takes when they turn it on.

Dave.
 

Offline poptones

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #9 on: August 22, 2012, 12:06:17 pm »
Right, but I meant the reason for the potting compound beign the goopy type. It appears from the teardown the opening into the baro sensor was contained within that stuff - and that fits the way the Ford sensors were as well, even having the sensor itself potted. But using the goop allows deformation, which allows the baro reading to migrate across  the barrier.
 

Offline N2IXK

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #10 on: August 22, 2012, 12:23:10 pm »


Yes, it would be either the "sealed" gage type, or a vacuum type. Terminology can get mixed up sometimes.


Here's the categories I am familiar with (US terminology and units):

Gage--Referenced to local atmospheric pressure. (PSIG)

Differential--2 ports.  Reading is the difference between 2 applied pressures. (PSID)

Absolute--Referenced to vacuum. At sea level, reads ~ 14.7 PSI (PSIA)

Barometric--Referenced to 1 atmosphere (14.7 PSI or 101 kPa).  At sea level, reads ~ zero.
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Offline PeteInTexas

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #11 on: August 22, 2012, 01:24:23 pm »
I wish you turned this on with a vacuum pump attached to the sensor before taking it apart (further).  Would it have been possible to activate with a vacuum pump like the one used in automotive repair?

And that "F" marking on the metal casing is likely not "fail".  I mean why bother sealing up the plastic around it if it does not work and risk mistaking for a working unit.
 

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #12 on: August 22, 2012, 02:04:19 pm »
I wish you turned this on with a vacuum pump attached to the sensor before taking it apart (further).  Would it have been possible to activate with a vacuum pump like the one used in automotive repair?

Maybe, but you have to get the rate of charge in pressure correct for it to activate. Not so easy I suspect.

Quote
And that "F" marking on the metal casing is likely not "fail".  I mean why bother sealing up the plastic around it if it does not work and risk mistaking for a working unit.

Umm, that was a joke.

Dave.
 

Offline PeteInTexas

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #13 on: August 22, 2012, 02:31:25 pm »
I wish you turned this on with a vacuum pump attached to the sensor before taking it apart (further).  Would it have been possible to activate with a vacuum pump like the one used in automotive repair?

Maybe, but you have to get the rate of charge in pressure correct for it to activate. Not so easy I suspect.

You think if the rate of pressure increase is greater than a certain point it WONT activate?  I can see if the rate is slower than a certain point it wont activate so as not to activate in the helium balloon basket in case of an aborted jump.  But I don't see why they device should care that it is falling faster than free fall.

Even if the ADC could not keep up with the rate of change, at the next sampling micro will realize it is at or past the reference point and, thus, I would think, activate anyway for liability purposes and/or comic relief.
 

Offline Bored@Work

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #14 on: August 22, 2012, 03:05:03 pm »
The connector design around 6:40 in the video is probably to have some test pins accessable from the outside, and/or to support different pyro attachments.

Getting such a device type approved must have been a nightmare. Maybe they needed innitial approval from multiple  national authorities involved, and then even more authorities when going international. Showing the thing won't go BANG while in the aircraft but will go BANG when it should. I won't be surprised if they have a shelf rack or two filled with paperwork for the type approval.
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Offline SeanB

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #15 on: August 22, 2012, 03:18:54 pm »
It would be a sensor with a range of 2 bar from absolute. Very sensitive and a large output. Easy to sense using a few small slots left in the case join, and reliable, as the volume in the case provides a noise reduction function.

As to the pyro and the capacitor, they want to have enough current to fire even at the point where the cells are frozen into slush. Normally the pyro only will fire if you pass over 1A through it, it is safe to test at under 1mA( self test during power up)
 

Offline tom66

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #16 on: August 22, 2012, 04:29:52 pm »
Love the partially decapitated TO-220s! I wonder if they had enough purchasing power to order those in or if they were factory modded?
 

Offline G7PSK

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #17 on: August 22, 2012, 06:00:10 pm »
The sensor worked due to the can was not sealed to air pressure, The flap over the jumper pins was not completely soldered around the edge, The F was most likely the a reference to the jumper pin position. i also noted that the gloop inside did cover the entry to the pressure sensor. Is there any solvents for the potting gloop.   
 

Offline icon

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #18 on: August 22, 2012, 06:57:26 pm »
Type approvals: I'm no doubt going to be proved wrong, but I don't think type approvals are involved. If there were, you'd think they would be all over the manual/website. I think they were first into the market with a device of this type (there were other more obtrusive/clockwork things around before) and they built a reputation for reliability. They've joined that class of manufacturer whose product name is now used for the product type, regardless of manufacturer.

RTC: the device is designed to switch itself off after 14 hours, so presumably that's what the RTC is for.

Cutter drama: I don't think there will be any. The 'event' is completely contained by the casing, so only the cutter moves. So they say, and I've never heard talk of a container being damaged by heat or explosive discharge (they're made of low-temperature stuff like nylon).

John
 

Offline murban

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #19 on: August 22, 2012, 07:27:19 pm »
Hi there,

Felix Baumgartner will use a specially enhanced version of a Cypres device when he jumps from 36,6km (120,000ft) achieving to break the sound barrier while in free fall...

http://www.redbullstratos.com/technology/backup-safety-systems/

regards,
Michael
 

Offline mtkaalund

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #20 on: August 22, 2012, 07:56:51 pm »
I would think that the RTC is for two things, one is so it can turn it self off, and the second is used as a precision timer.

As for the precision timer, it is probably used to do some math, so that it calculate that it needs to fire the pin and deploy the parachute.

or the timer is for pulling the ADC with a specific interval.

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Offline Ed.Kloonk

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #21 on: August 22, 2012, 09:33:38 pm »
I wonder if the cap in the battery was due to them finding the battery couldn't give enough power to fire at low temperatures, or they were worried about electrolytic lifetime, so it gets replaced when the battery is changed....

When are you going to try firing the pyro..? I think it should be attatched to a rope from which a large anvil is suspended, with a pile of crappy multimeters below.

I had exactly that idea!
I don't have an anvil though unfortunately.
I need to bring some gear home to do it, don't want to do it in the lab lest there is any loud noise, or smoke that sets off the buildings fire alarm!

I've used almost identical sized lithium primary batteries in a military design that had to work down to low temps and there were no issues with driving a high current heater element.
Yes, maybe worried about lifetime, although I'm not sure what advantage there is to having the cap across the battery that far from the circuitry.

Dave.

I learned the hard way about lithium batteries. I used to take a Garmin etrex-h GPS (yes, just like yours. A really great device) into the snow fields. The first time I thought I was king shit with Lithium batteries from Coles as they lasted the whole trip of Egypt without any problem.

Of course in the Japanese Alps, I was horrified at the performance on the first day. I had my hotel manager send a SOS for some Alkalines- which I used religiously until I got the so-called smart phone.

I now find I have to keep the android close to my chest to keep it awake. It has a god awful Belkin battery pack stitched together with Velcro and gel contact glue so it will last the day out.

I call it the Franken-Phone. Should post a pic of it. You guy's would be mortified at my sheer hacked-ness.
 :)

Oh,  nearly forgot. I enjoyed the video, Dave thank you. BTW, the link to the forum topic from the main page "404ed" me. Just to let you know.

 :) :)
 

Offline mgregg

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #22 on: August 23, 2012, 03:29:54 am »
Great discussions.

Dave, I'd be very interested in seeing the cutter function.

Several things to note, apparently the cutters seem to only function when operated on line under some tension. If you try to cut line that is slack, you may not get a cut.

Also, that cutter is specifically designed to cut 2 or 3 mm Spectra cord, but it should cut similar thickness dacron or nylon cord just as well.

If you would like to try this thing out on some actual parachute line, I'll happily mail you some. (please note, most of the stuff sold in the sporting goods store as "parachute cord" will never be used in a skydiving rig.)

Also, somebody mentioned the RTC. As best that I can tell, the RTC is only used to determine the age of the device.

Those things tell the user to send it in for testing and service every 4 years, and they report themselves as completely useless after 12 years.

Given the sample rate on the pressure sensor, and the fact that the RTC only has a precision of 1 second, I am prettu sure that they are not using the RTC for calculating if it should fire the cutter or not.

Oh, another use of the RTC could probably be to determine when to switch to low power mode. They automatically shut off after a day of jumping.
 

Offline dirkie

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #23 on: August 23, 2012, 05:44:01 am »
Here is a cutter in action. (with a steel cable)

 

Offline mgregg

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #24 on: August 23, 2012, 06:16:29 am »
wow, through a steel cable!

Cool to see. Rather non dramatic though.

I guess that's why I spend so much money on those things.
 


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