EEVblog
VloĆŸit
- Äas pĆidĂĄn 9. 08. 2016
- Defibrillator Teardown!
Inside the Heartsine Samaritan Pad AED heart defibrillator.
Forum: www.eevblog.com/forum/blog/eev...
Datasheets:
www.mouser.com/ds/2/205/CS20-2...
www.vishay.com/docs/94386/vs-3...
www.mouser.com/ds/2/196/irg4ph...
www.fairchildsemi.com/datashe...
www.promelec.ru/pdf/ISD4004.pdf
EEVblog Main Web Site: www.eevblog.com
The 2nd EEVblog Channel: / eevblog2
Support the EEVblog through Patreon!
/ eevblog
EEVblog Amazon Store (Dave gets a cut):
astore.amazon.com/eevblogstore-20
T-Shirts: teespring.com/stores/eevblog
đ Likecoin - Coins for Likes: likecoin.pro/@eevblog/dil9/hcq3 - VÄda a technologie
A defibrillator does not restart the heart. It stops a dysfunctional rhythm. A very common misconception
Right!!
Whats more it can only treat certain kinds of shock able arrhythmia and it does so by stopping the heart in hopes that it will restart its self in a proper rhythm.
Does a dysfunctional rhythm in the heart give off a pulse and if so how do you know when to use the AED?
layman's terms
+Star250 If a person collapses and they have no pulse attach the AED. It will analysis the heart rhythm and decide if it should deliver a shock or not. It will then prompt you to either press the shock button or not.
Hi Dave, I think the reason for the internal coin battery is that these devices record the heart rhythm for later retrieval at the hospital, or for the ME (Medical Examiner). Those contacts which attach to that USB cable is what they use at the hospital to removed that data. Plus the clock circuit would be needed to record how long the machine was turned on, how long the patient was in a certain type of arrhythmia and the waveforms before and after the shock was delivered. All that data is recorded and used for statistical analysis.
Sad thing - this has to be so much 100% reliable and certified that finally it's price prevents it from becoming widespread. In the end, instead of having a 99.9% reliable defibrilator, you have none in the place and the patient dies.
Actually, in the Netherlands theyâre everywhere
As an Irish man, I am delighted that Dave said "Hi to all my Irish viewers" instead of "Hi to all my British viewers"
For incident logging, you read the current RTC value at time of readout, and subtract from the timestamps in the log, so only the drift between the short interval between incident and readout matters. RTC may also be used for expiry/service interval enforcement
I was going to say almost exactly the same, after use they pull the data, they can apply a time correction if needed.
Or may be the RTC is used for the Expiry Date. Something like if it expires (goes over the date specified on the device label/programmed into the IC) it stops working? Dunnno, may be another explanation that i thought about after i saw the actual device has an expiry date?
why you copy my profile pic
*facepalm*
Yes, of course. Forgot about that.
We used to do this with seismic data loggers. Even with the best clocks we could get there would be some offset, so the data is read back later and drift correction applied across all the loggers.
Several nice components to salvage. Very nice teardown.
In reference to the caps you were wondering about, Cornell Dublier makes a lot of special pulse rated caps so they may be just a jelly bean part for them. A lot of people use them for huge cap arrays in large Tesla coil designs because they can handle the stress of a disruptive discharge circuit, being charged and then discharged at high frequencies through a spark gap. As I'm sure you know, if you try this with just any old HV cap it will most likely explode.
Yes! Tear down that isolation probe.
I would really like to see more EEVblog of medical stuff like this! This was a bobby dazzler of an episode.
I'd love see a teardown of the LeCroy differential probes.
+1, I really wonder why these things are so damn expensive. Maybe make a EEVblog div probe?
I'd like to see that too. The are so handy for measurements in circuits with various ground levels.
They are a niche market. But even the cheap brands are 3-$400
SCR Fundamentals Friday would be lovely, too.
+EEVblog And there are not so many different OEMs. We have several brands that look exactly the same
Your voice is almost like Shepherd's Tone. It seems like it just gets higher and higher and higher and then starts back again at a lower tone, only to seem to get higher and higher again. I dunno if that's just natural talent, or if you worked on that for a good long time, but I love it!
Oh another one! I love these medical tear-downs!
I am a veteran IC paramedic. one thing that has amazed/anoyed me is how much markup there is on AEDs in Australia. What you can get for a few hundred dollars overseas costs 800 up in Australia. That is market protection for you. There was a rule to have them in public places, but they were stoled by low life people, so the law was relaxed.
Very cool teardown and analysis!
Would love to see a differential probe reverse engineer and teardown. Love the videos Dave, thanks for all you've taught me so far!
one of your more interesting videos. I love the pondering of why the designers made certain decisions
...and of course the legendary "Wun Hung Low". At least you gave us a "Bob is your uncle" on this one. Thanks :)
Dave,
Love your Vblog! Keep it up please!
For the clock, maybe a relative time works just as well ("I was activated 10 hours and 15 minutes ago").
I also wonder if the clock could be used for the expiration date of the pads - it could refuse to activate if they're expired.
the expire date on the pads is exactly for the adhesive/conductive paste, since if it dries off too muche there might be problems, especially in men whith a lot of chest hair that already raise the resistance of the patient quite a bit, in fact in the AED pouch we have also a smal razor blade to shave the area (of course it very much depends on the situation if it get used or not)
I agree about the clock- but I do not think the device will refuse to work? Friendly voice saying : I am Sorry- I am expired and your dead?? I would expect who ever installed it is realiable for swapping them in time? Would be interesting to know though....
My instant thoughts of RTC were for expiration.
Absolutely fantastic demonstation. Thank you. I will be contacting you regarding some clarifications. Thank you for putting this online
I love these teardowns, the re'ing and the DaveCAD drawings. Please give us more ;)
The usb cable is mostly for download the recorded data. When the pads connects to human body, it can act like a heart monitor that constantly record data to its internal memory and doctor can get those data by the usb cable.
Interesting teardown as usual but we didn't get to see those big chips up close this time. Aww. I'll have to look at the hi-res photos.
Absolutely! High-voltage sensing is important for a piezo project of mine!
Really well explained, thanks Dave!
SCR Fundamental Friday! Sounds like a good idea Dave!
Maybe he could then tell us how a scr turns off while current flowing through it...
I think they used the IGBTs therefore...
For someone who has one in his bag at work! (never used apart from training) this was great to see! and as for the probe teardown, when don't we want to see you rip something apart!
These things are not for when someone gets a heart attack, which is when a blockage occurs in the blood vessels of the heart and the heart is deprived of oxygen. This device is to restart an arrested heart.
Oh, oh, oh. Lifepack 15 teardown!
Awesome video. Thanks!
very nice tear down, thank you
PUT: Patient Under Test.
If the equipment doesn't work, you are ka--put! Makes sense.
When I heard him say that that was Hilarious ...
In my land it's ka-putski
PUS Patient Under Stress.
+Google+ is Censorship I'm not getting involved on that stuff... running the other way. If it blows I don't want to be anywhere near it.
Use flux to flow
Cracking video, Dave. Enjoyed that greatly. A Big Thumbs Up! :)
The one I trained with had similar labelling on the pads, one for the chest, and one lower, but the plug wasn't keyed, so they could go either way.
The key thing about those electrolytic capacitors is that they are +/- 10% tolerance unlike a bog standard 'lytic that can be anything up to +80% -20%. For this application, that means that for a given voltage, the pulse energy is guaranteed to be the design value +/- 10%. It also means, for capacitors in series, that the charge will be more evenly distributed among the individual caps.
the rtc is most likely there to be able to schedule self tests. you can most likely get the test report using that USB cable.
Dave; 2:33 ; an aed does NOT give a shock when you have NO hartbeat. Only when the hart fibrilate it will give a shock. Its one of the things a lot of people doesnt know. The aed will tell you then to start hartmassage and checks the progression.
The AED cable is used to download the data of an incident. The waveform data and shock data can be downloaded.
YES! Dave, please do an Fundamentals Friday on SCR and TRIAC's and such, would be amazing.
Great tear-down!
I see a lot of good quality usable parts perfect for robotics,other such projects,even a battery jump starter. lots of tear down goodness in there.
I'd certainly like to see the differential probe teardown.
Very Interesting!Neat drawing! :P
Hi Dave! Yes please, make a video about differential probes! Why are they so expensive ? What's inside? is it reasonnable to build your own, regarding safety issues? Would love to see a dedicated video to this topic.
Nice video Dave, Could you test this device and show the waveform on the oscilloscope ?
I hope your leg is now feeling a whole lot better.
Very cool teardown! Love the reverse engineering ;)
I'm very interested in medical devices and want to choose this field for my master studies, so I'm looking forward for other cool teardowns like this =)
cap+ and cap- terminals may be for an external cap for other models.
Or instead of, for a different build version.
traces are bit smaller than the onboard caps, you'd expect that if it had external pac the traces would be of least the same thickness. I would suspect its more likely that its for diagnosis.
I would say that the trace widths are a little mixed up. The traces between the caps are significantly larger than anywhere else on the board. Not to mention that caps series have an overall reduced capacitance. So they're in series to achieve the desired voltage and not power. So i suspect that the output current is not what you suspect at the sight of the size and number of capacitors.
You'll also notice that the traces where the pads plug in to the board are a very similar width to the cap+/- outputs.
I would say that they're for a different model. It seems like a bad idea to have those traces just for testing
i suspect they are for a Coulomb counting rig to validate the actual installed Joules at EOL test? ie, device put into test mode, charges caps to defined voltages, then rig slowly discharges them though some resistance and integrates the total current that flows?
Maybe, but the traces are smaller
It says to apply CPR if needed, because a shock isn't always effective. For the AED to work, the heart must be in a "shockable" rhythm, like ventricular fibrilation (hence the word "defibrilator). Some other rhythms including a complete flatline aka asystole can not be fixed with a shock. In these cases CPR must be performed first, which hopefully pushes the heart into a different rhythm that is shockable.
I am obviously not a doctor. Don't take medical advice from a comment on an EEVblog youtube video.
I'd love to see the teardown of the probe as well! I may be confused though, with the second phase: Would the relays need to open in order to shut the SCRs down between phases?
How can the SCRs turn off, when there's still voltage on the caps/current flowing?
The clock maybe just there to start beeping, when the time for the pads is up or there is some calibration/check to be done at certain intervals.
It's worth mentioning, these shouldn't be used on someone having a heart attack. They're intended for people suffering cardiac arrest, and may actually cause more damage if used on someone suffering an infarction!
Might caps are pre charged on factory via these pins?
The flyback diode(s) you were looking for is inside the coil, you can see the silver coloured terminal going into the air core from one side. They used a PTH one instead of the two SMD ones.
surprised not to see a microphone. most of these start recording audio once they are turned on.
So the transformer on the left of the davecad is creating the high voltage/low amp?
I was kind of expecting him to fire that thing up and show some scope pics off the pads of it doing what it was designed for.
Dave, can you explain how the positive pulse is terminated?
How can you be a fan of MELF res. and diodes when they start rolling away when you try soldering them? It's painful!
I miss "We're in like Flynn!" Dave. That and "Bobby dazzler" and "trap for the young players" are kind of your "catch frases". Don't stop saying that. :)
A teardown of such a probe would be most useful if it came with enough information to create a DIY one. There is just so much lab equipment a hobbyist can not afford that seems to be hard to create yourself but when you went through its details, it isnt that hard anymore.
Is it considered good engineering to put diodes in parallel with a string of capacitors in series? Are there any general guides as to when and when not to do it?
Please do a Fundamentals Friday on IGBTs as well.
at 15:30 that voltage sense circuit across the caps - would that be a little ADC that reports to the microcontroller?
How do you turn those top two SCRs off with current flowing through them?
+EEVblog Dave at 29:30 you're talking about the lack of diodes across the inductor. What I've been wondering is where does the energy in the field go since I didn't think the reverse spike would go through the SCRs. Is it just dissipated as heat somehow? I hope you don't mind the question, I'm just trying to get to grips with some fundamentals since its nearly Friday!
Could the RTC some form of old age protection?
For your question on whether the caps should be medical certified, YES they need to be medical compliant.
I almost thought that red inductor thing was some sort of part for current sensing like they use in GFCIs, etc.
Just wondering if anyone could explain why you need the caps? Why can't you just output the required DC current and use components to control the voltage/current/waveform etc? I am just learning by the way so hope this is not a daft question. Thank you
Is there a specific name for the diodes which prevent the series capacitor bank from reverse charging when its discharged? My search has only been showing balancing resistors, but no diodes.
Hey Dave, I see a lot of the components on the HV side are only soldered onto one side of the PCB (e.g. the dropper resistors at 15:33). Why is is so? I always thought that a two-sided Pad will help stress relieving when the components wiggle a bit. What are the advantages of a one-sided through-hole pad?
Also it looks like the outermost pads on the high voltage transformer are missing on the pcb footprint, or does it only look like it?
What's the main microcontroller? Also, why do they use IGBTs for the negative wave circuit?
We need a LeCroy differential teardown, yes yes, take it apart
im really interested in making a floating ground probe, might get some inspiration from the design, i'd love to see a teardown video on one of this
I will love to see a FF on thyristors. Love the vid :)
Am I correct in thinking that those missing diodes on the inductor are because of a different model or a previous design revision? I noticed a lot of boards will have missing components where they are marked on the board.
27:23 Don't the relays have to open in order to turn off the SCRs? I thought that SCRs continued to conduct no matter what happened on the control pin.
I suppose that the IGBT is there in order to stop the discharge in the middle of the biphasic pulse. Maybe I am wrong, but the Thyristors shouldn't stop until the whole capacitor finished discharging, unless the IGBT turns the current off in the middle of the pulse?
Why the IGBTs and not more SCRs?
Wow. Like the multi-layer version of Dave Cad. Cool. I'm not very clear on Thyristors... what use them? rather than a power transistor of some kind?
I liked the video, but I wish you went over the digital micro controller section of the board. Maybe a part 2 teardown video?
Belfast is Nothern Ireland (part of the UK)!
I'm curious, what is the black circular component with a hole in the centre, it's the one on the battery side and has two white things next to it? đ€ my computer motherboard has one too..
It's a small speaker.
How come on that monophasic vs biphasic diagram, the monophasic looked like it went below 0?
Is that just a printing error or is there a simple reason behind it?
The equipment might use the RTC to regularly do self tests and the Usb might help readig the self test data out to determine if the equipment is still in good condition.
John Doe is that the battery he was talking about? was thinking it might be used to set off an as alarm after the device gets too old.
The AED's at my work record all the patient information and can tell if you perform CPR or not...might be the reason there is the crystal and chip you were wondering about. We have had the information in the AED requested via subpoena for a lawsuit.
A thought for Fundamentals Friday:
Design of resistive voltage dividers for cases where the measured voltage is greater than the supply of the opamp or IC measuring stuff?
Hi dave
FYI, that cable thingy is for Firmware update and for training.
my friends runs an R.T.O. for Paramedical Training
the cable plugs into the AED and then other side into a Rhythm simulator that the instructor can throw at the trainee medic
while the dummy is hooked up to the defib
all the instructor has to do is press a button and select different cardiac conditions
the device is basically a glorified waveform generation
take care mate
as always
good videos
PAD AEDs don't have a training mode (and aren't used by paramedics). AED training is done with cheap 'trainer' units that don't have capacitors, etc, just a speaker, some 'smarts' and an IR receiver that lets the instructor control it with a remote. Training for more advanced units used by paramedics is done by simulating the heart rhythm directly through the EKG leads. The heart monitor doesn't know it isn't hooked up to a real patient.
The USB cable is used for firmware updates, as you mentioned, and to download a 'replay' of the incident if it is used.
Please do the teardown of the differential probe
Maybe the stickers on top of the electro's are for leakage current matching, I didn't see any balancing resistors for the series bank, so that would be my best guess.
Awesome
PUT! Oh, yeah! Thanks, Dave!
Something doesn't add up. Once the TPS SCRs are triggered, how does one turn them off before firing up the negative pulse?
It does not matter if the RTC drifts over the years as you just need the time between the use and readout of the log which should be happening within days or weeks at most, where the RTC is going to be really accurate (seconds is good enough anyway).
Dave please make this explanation for Arduino. This I understand most of it would be helpful to me and I believe and others with the Arduino board to understand more of its microcontroller. Your knowledge is deep, and you know what you're talking about, I believe that with your help and with your Arduino Teardown plus scheme like this. I'm not asking all the details, but I was grateful to learn something more from you for Arduino. After all you are the best.
The RTC could also make the device start shouting that it has expired.
Imagine one of those at a mall yelling that it's out of date. Would get replaced fast. Or thrown in the trash and forgotten.
They have one of these at the local Mini market (Co-Op for those in the UK) down the road. Hope it never needs to be used, but may do a great job if it is.
I'm surprised to see that there isn't any milling out around the HI Voltage areas for creepage.
Maybe those are water test dots, try getting one of the stickers wet a bit to see if it changes colors?
During my cpr training, they told us to leave the leads and pads alone after shocking... the whole shebang goes to the hospital with the patient and they'll pull the data there. So the absolute time isn't as important, just relative time.