Author Topic: EEVblog #339 - Cypres Parachute Teardown  (Read 16251 times)

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Offline tom66

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #25 on: August 22, 2012, 09:36:38 pm »
Love the decapitated TO220's...  Custom bodge or ordered in, I wonder?
 

Offline EEVblog

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #26 on: August 22, 2012, 10:03:00 pm »
i also noted that the gloop inside did cover the entry to the pressure sensor.

No, the pressure port was clearly sticking out of the goop when it was first opened.

Dave.
 

Offline mikeselectricstuff

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #27 on: August 23, 2012, 07:41:23 am »
Re RTC - remember this is 1990s tech, when sleep modes etc were basic if they existed at all. The RTC's main function is probably to wake the CPU periodically to take measurements, as well as keeping track of run-time. I wouln't be surprised if it was actually powering the CPU on & off.
 
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Offline Majorstrain

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #28 on: August 23, 2012, 03:46:35 pm »
It's possible that the pressure change is facilitated via the inside of the multi-core cable from the button unit. If there was no goop sealing the cable at the button unit end as is the case at the MCU end, then unit pressure would change quite readily.

I've used similar, if not the same sealing compound in load cells. It was called ' Silicone dielectric gel '
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Offline Rising Edge

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #29 on: August 23, 2012, 06:27:33 pm »
Hi,
on the 'Safety Bulletins' Page, found on the website of the manufacturer, your can read interesting things about problems (recalls), they had in the past. One of them caused by bad sensors in the waver production state.
In 2007, they were in Ayers Rock (Uluru), Australia to make tests with possibly bad sensors in higher temperature areas.

Then, two 'fails' occured also in Australia...no one was harmed.
They give statements about their responsibility for the quality of every produced device.
To reach their high quality aims, they also "treat" the sensors in their factory, after they bought them from the 'sensormaker'.

http://www.cypres.cc/index.php?option=com_content&view=article&id=163&Itemid=115&lang=en

Bye
 Ingo

BTW: Excellent work Dave. I can't get enough videos to watch from your EEVblog. 8)   
 

Offline amyk

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #30 on: August 24, 2012, 08:06:38 am »
Probably a 68HC11/HC12/HCS12 MCU in there, given the presence of the RTC. A surprisingly large package, for the number of devices it interfaces with (a few buttons, ADC, RTC, pyro firing.)

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.
Not surprising, it's designed to cut through the cable quickly and not to blow the whole thing to pieces.
 

Offline ot1

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #31 on: August 24, 2012, 10:37:50 am »
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.

The timers in the MPU would be used to control sampling interval, and the auto shut off, sleep mode.  Pressing the on button wakes it from sleep with an I/O set as an interrupt to wakeup.
The RTC would be used to flash the Get Service Message after 4 years, not sure is the device becomes useless after 12 years, or some sort of end of life interval stored with the RTC.

Interrogating the RTC every 2 seconds is pointless when you can easily do it within the MPU even for the 14 hour sleep mode (60*60*14), easy with a 16 bit variable.

 

Offline wingnut

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #32 on: August 24, 2012, 03:35:07 pm »
Hi, I watch your eev blog videos but this is my first post on your forum. Very cool to see this teardown. I'm a recreational paragliding pilot and also design variometers used for gliding that indicate your sink/climb rate. I actually have one of my open source audio-only designs in production as the "Microvario" at flytepark.com.  Just a few weeks ago, someone asked me if it could be adapted for skydiving use. I did a few training AFF jumps in 1994/1995 (never graduated the course), and remember the cypress AAD from the skydiving mags back then !  A lot of current flight instruments are like this - late 80's designs, I have no idea how they maintain stock of the required components.

I can speculate on what it does. You would have to set the LZ /airport altitude, as barometric pressure sensors only measure pressure altitude, i.e. w.r.t. air pressure at sea level. That can change by +/- a hundred metres due to weather changes, so you need to set the ahem "bounce"  altitude before you get into the aircraft.   It would then measure two things, absolute altitude w.r.t. to the reference altitude you just set and the rate of change of altitude (obviously you don'
t want it going off when you're floating down under canopy). The way to do that is to sample the altitude at regular intervals (say several milliseconds) over a rolling window of time, e.g. the last couple of seconds worth of data, and do a linear regression of the altitude samples. That gives you the slope of the best fit straight line to the noisy altitude samples. This is your fall rate.

My answer to the guy who asked me whether my project could be adapted for skydiving is in your teardown video, and your comments - this is a life saving device, and would need a huge investment in calibration, certification and maintenance procedures. That's an analog device that would need a calibrated pressure chamber. These days you get $7 digital sensors e.g. MS5611 that have their calibration coefficients in ROM and are probably far more accurate and less noisy than a board level ADC circuit. Even then I wouldn't want to be responsible for certifying the design for life saving applications.

Random thought 1 : I have seen references in pressure sensor datasheets to Goretex type material  that  allow pressure sensors to sense atmospheric pressure, and still maintain device waterproof rating.

Random thought 2 : I know a skydiver, who takes his kit as airline cabin baggage - when he takes it through security, there is a laminated card from the manufacturer that he shows to the xray folks to convince them that the pyrotechnic device is safe and has been disabled via user menu, for the flight.
 

Offline Richard345

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #33 on: August 24, 2012, 08:59:35 pm »
Maybe, but you have to get the rate of charge in pressure correct for it to activate. Not so easy I suspect.

Hi,

Nice video again, so I finally signed up here after a long time watching your vids, especially the teardowns.

Such pressure things can be tested very easily and quite precisely using a disposable syringe. For example, if you pull it open for ten units, attach it to the sensor, and then pull it open for two additional units, you should be able to trigger this device with a pressure difference corresponding to something more than 1500 meters.

-Richard
 

Online G7PSK

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Re: EEVblog #339 - Cypres Parachute Teardown
« Reply #34 on: August 25, 2012, 06:07:23 pm »
i also noted that the gloop inside did cover the entry to the pressure sensor.

No, the pressure port was clearly sticking out of the goop when it was first opened.

Dave.
Another typo I am missing a "not"
 


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