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- čas přidán 29. 10. 2014
- In this tutorial Dave explains what a PCB spark gap is and how it can be a useful zero cost addition to your PCB layout to help prevent ESD damage.
He shows how to easily design them into your board and calculate the approximate voltage rating.
And of course has some fun applying 5kV to some gaps to show how them at work.
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You should make an episode all about components that can be built out of pcb races like pcb capacitors, fuses, inductors, antennas, transformers, there are so many options!
Agreed!!
That is an awesome idea for an episode!!
Transformers? Really? Wouldn't that be more like coupled inductors? Or do you have to add a ferrite bead?
I would be all ears for a full fledged input protection tutorial!
Back in the 60s, I had an RCA color TV come in that kept blowing a fuse. I discovered two parallel traces that had arced across and the PCB had become carbonized, kind of a low-Ohm resistor. I ended grinding out the carbonized area and painting it with a high-voltage coating that is normally used around the second anode connection on the CRT. That tamed it... :-))
Should've used peanut butter on that fuse.
TVs don't like blowing fuses when there's peanut butter on it.
No idea why this appeared on my recommended, but I'm glad I clicked it. I learned a little bit, and this was oddly relaxing to watch. Thanks.
Beautiful class 3 soldering as well on that PCB. I am class 2 certified, and while I cannot remember the exact numbers, I think they are roughly these for through hole components.. Class 1: it simply needs to work. 50% full in barrels, 50% wetting on the source side. Class 2: it has to work for a long time. 80% barrel fill, 75% wetting in the source side, 50% on the destination side. Class 3: medical grade devices. 100% barrel fill, 100% wetting on source side, 80% wetting on the destination side. Class 4: aerospace and military applications. Perfectly wetted and filled barrels.
I never seen intentional spark gaps on PCBs, thanks for sharing!
Dave, thank you for listening to your viewers and for making videos about the things they ask you about. You're awesome!
Absolutely brilliant overview, very layman level. Sometimes, I have to admit, you post things that fly past me, but this video is really comprehensive and explanatory.
I use software for protecting inputs:
int main (){
if (voltage > crappycomponent II voltage > pcb_resitance){
gap = 0;
if (smoke < cigar) {
repeat = 1;
while (repeat){
trace = releasesmoke;
repeat--;
}
printf("shit hit fan");
return 0;
}
Seems legit. 10/10 commit.
What language is that?
I'm genuinely curious if that would work.
repeat = 1:
while (repeat){
trace = releasesmoke:
}
That's an infinite loop, by the way.
@@TorutheRedFox looks like C for an Arduino or STM or something
@@joshfixesall4056 That could be C or C++
Arduino doesn't have a main() function.
i dont make boards, im not knowledgeable about this thing and does not have any background about electronics. But i find my self watching a lot of your videos!
Kitsune Ken Welcome to the club. ;P
😭 you doing this nothingness !
Being in the field for some 30 years, it's refreshing to learn something new. Great video.
Hi Dave, I appreciate very much your work. I miss fundamental Friday :)
InXLsisDeo He's already done LTSpice, and Afrotechmods has already done the switching power suppply basics. mikeselectricstuff has covered supercaps too.
I like the way Dave speaks on here.Calmer.Interesting videos.Thanks.
I'm really liking the inclusion of an example in a CAD package. Thanks!
Thankyou for this video. It was entertaining to see the spark gaps in action, and most informative to see them designed on a PCB maker.
Awesome, Dave! I was wondering about this myself and searched for more info online, but came up with nothing. Thanks!
+ EEVblog Pretty Good Video Dave. You say most IC inputs are pretty tolerant of ESD these days. You're right; here's a story of .the early 1980's when they weren't ... We built an experimental 2-D phased array which was digitally steered. Each array element had a 1K deep 8 bit CMOS FiFO on the input. We had just finished integrating & testing the digital part & were ready to start the RF tests. On that cold, dry morning, one fellow came into the area behind the antenna & peeled off his wool sweater. He was right next to the big digital backplane but did NOT touch it; didn't matter - ALL tests which had passed 2 minutes before, now failed each & every FIFO was fried.
This remembers me about electrostatic experiments in school when it was summer (exact opposite). They just did not work.
But still today there are many modules in RF that have a very low ESD Tolerance of just 500V to 2 KV.. bad for the bom cost
Great video Dave! Showing us how to design spark gaps in your PCB software was fantastic. I would love to see you incorporate more of that when you discuss layout related topics, because it's great for visual learners.
Here is another viewer from the Kurdistan part of Iraq. Yes we love you Dave
Kurdim same from Baghdad :)
First time I see it, funny that the circuit passed medical standards! Even though I would never rely only on that.. Breakdown voltage depends also on humidity of atmosphere around for example
Cheers!
Redesigning a serial terminal interface card, we added pcb spark gaps because built ones cost a fortune! Spark gaps+ Rc networks worked a treat solving our ESD problems!
Awesome explination for those who were unsure. Basically if its going to fair somewhere then make a weak point thats safe from IC / chips. Spark gaps are great little protection features of PCBs so make sure to add one if needed.
I'm glad that electrical engineers care about ESD nowadays. Back in the 80's it was a simple matter to destroy one of the joystick ports on a Commodore 64 simply by using it. In those days the ports were used a lot. It was uncommon to plug in a joystick and leave it plugged in for any length of time like it is today with consoles. In particular I remember using one port or the other, depending upon the software.
This is the greatest person on youtube, bar none.
I just realized now people love to watch someone plays video games for them, pretty much the same as we watch how Dave does all these interesting stuff for us! Great work! Thx, Dave!
Love your channel, every video is interesting and very informal.
lovely demonstration & explanation. thank you for posting. take care & stay safe.
Thanks Dave. I don't remember ever seeing such a crude spark-gap before on anything I have fixed.
Thanks, I was just looking into spark gaps for a design and this video showed up on my feed :D
Great description, I was wondering it myself!
Loved that you went back and tried the lower setting after the spark gap had burnt.
+calvinthedestroyer Me too. I wanted to see if it would arc from the carbon track it made. Thought for sure it would.
The most interesting & biggest spark gap's you'll see (inline before the gase discharge) are in commercial AM/FM transmission lines, usually set 180°from a right angle of transmission line.
As always, great video - and thanks!
I suspect that PCB spark gaps are used a lot less these days of lead-free solder. Tin whiskers anyone?
AIM54A I don't recall that, so would like to see it!
The safety spark gaps I've designed have always been gold plated, both to prevent oxidation, and to mitigate the whisker issue somewhat.
Sarcasm not indicate so here goes... Not I'm any sort of expert, but wouldn't depending on tin whiskers would be as bad on depending on a spark, or even worse? You can be sure the spark gap exists because it was purposely designed and manufactured. depending on whiskers means you're gambling they have been create & create in a manner that they had create in a manner they could provide the level of protection desired. You seemed to miss some important details in the video. Sharp point aren't desirable, while I'm no expert I understand why thee aren't. Also the spark gap should be as close to the power supply input as possible.
waswestkan
I wasn't suggesting that tin-whiskers be used -- I was simply pointing out that using lead-free solder without soldermask and with sharp points in the presence of a reasonable electrostatic field would be a perfect environment for the growth of tin whiskers that would (eventually) short out or reduce the gap, thus creating problems.
mausball
I could be wrong, but I thought xjet was implying one doesn't have design spark gaps, because could gamble on the creation of tin whiskers in a manner that would provide the desire protection.
I remember a line of credit card terminals I had to support. The metal casing was not grounded, and there were two traces with exposed metal mere millimeters from a support for the case. One trace went to a RAM chip, the other to a flash ROM chip. One ESD from the clerk touching the case, and it either lost all transactions for the day or bricked, depending on which gap the ESD jumped.
We have an insulation resistance tester at work that measures up to 200MΩ at 1000 volts. If you hold down the test button, it'll continually cause arcing if you hold the clips close enough together, and you see the measurement result jumping around.
If we do that when it's attached to a faulty cable (that doesn't have a full short circuit) the resistance slowly goes up.
I always learn a lot on this channel, thanks as always for youtubing
What I would like to see now is a Fundamentals Friday on better ways to handle input protection!
Great info Dave, thanks.
Thanks Dave!
I saw this thing(spark gaps) many times but didnt thinking its for protection :D
I see this very often on smps(eg. smartphone 5V charger/power supply).
Thanks for doing this video, had a SMPS but they put those on the common mode choke.
Beautiful . The carbon that is formed after a discharge in a solid, is conductive. Carbon residue is a good conductor. I agree that it would be better practice to remove the solid material from between the spark gap terminals . That is to have an "air gap" .
The sharp edges arc easier than flat or round edges. The sharp edge has less surface area so the current density is higher and will thus arc easier than if the current is spread over blunt edge.
You're so close to the answer, so close! But it's not current density, it's the density of the electric field. The electric field is concentrated at the tips of points and it takes less voltage to make the air there begin to conduct.
Dave's pointless (pardon the pun) spark gap is actually a pretty bad idea. Or rather, he's making its arc-over reliability far worse by not concentrating the electric field on a point to encourage breakdown. The idea is not to sustain continuous arcing, but to handle short faults (under a few ms). Same reason lightning rods are pointed.
Great video. Around 10 min I can see your reflection in that excellent solder joint. Ha!
Great video.
As RimStarOrg mentions in his videos, it's easier for current to travel through air if ther is a pointing thing like that you show us on the pcbs. The round think you showed as in the cad is not so good as the pointing one.
An input design tutorial would be awesome 👏
During the 1000 volt test a tiny speck of PCB material moved downward away from the upper C shaped terminal. So no spark, but still evidence of the HV.
I noticed that too
azayles Yeah, several have point that out, very interesting. Didn't notice that at the time.
azayles 12:25 In the valley in between the two lower left points you can see a spec of the crud shift in the 1kv test on this PCB as well.
Nevir202 Oh yeah! You have a good eye :-D
azayles
Thanks, don't know if I'd have been looking for it if you hadn't mentioned it before I saw that part of the video.
I've always wanted to see you play with high voltage.. I guess this is as close as it'll get =P
Fascinating.
In the early 1970’s, while working on a PCB for operating room EEG equipment, I was told that due to the presence of pure oxygen and flammable anesthetic gases, free air sparks were verboten. Fancy air-seal-before-contact power plugs, etc. were required. Are free-air spark gaps up to code (allowed) on medical equipment?
Does your formula represent maximum or minimum breakdown voltage estimate? Is the formula for a rounded trace end or a pointy trace end? Does air humidity have an effect (from high school Van de Graaff experiments, humidity is critical: high humidity seemed to cause discharge without a spark and a long-haired person’s hair wouldn’t flair out on a high humidity day) on pre-spark discharge? (But another comment stated that 50-100% humidity required 40/39th the voltage to cause a spark at a given distance than low humidity.)
Also, the more pointed the charged surface, the more concentrated the electric field which causes a spark, thus a lower voltage is required to cause breakdown, giving better protection, unless it overlaps mains peak voltage.
Another use-case for this protection is shorting-out back-EMF pulses from collapsing magnetic fields, e.g. in motors, connected to the same mains.
In your design discussion, you want to short out to “earth-ground”, not digital-ground or analog-ground, right? Or, at worst, the mains “neutral”.
I'd really like to see a video or series of videos on input protection just as you suggested. It'd be great to see this for both analog and digital (high speed and low speed, busses, etc). Maybe some tidbits on protecting against impulse/ESD vs slow ramping overvoltage vs long periods of overvoltage.
Anyone else just like seeing some High Voltage stuff? A part of me just wanted to see something explode. nothing better then venting some frustration with HV and some unsuspecting caps :-) love it. Id love to see a random video of component failure points too. :-)
Hi Dave, nice review! This spark gap is not for protecting the input of the device, it's for leading the voltage flashover when (for example) u have a surge of higher voltage between the primary and secondary side or as u said ESD. You can not compare it with GDT. These gaps are also often being used in parallel to each winding of a common mode choke. If u have any question in detail to this PS I could ask my college at work, that's his baby ;) Greetings from Germany // Kaneda
In combination with a resistor it would protect the IC from ESD, wouldnt you say?
Excellent Video!, thanks
"...argue until the cows come home". I laughed so hard. I'm German and didn't know about this phrase. Nice one! :D
PS: I think it was a phrase of farmers back in the day, where a long time was described to be until the evening where the cows came home.
en.wiktionary.org/wiki/until_the_cows_come_home
I would love a video about input protection! Tips and tricks!
Thanks for the video, Dave!
if you need some ideas for some follow-ups: I would very much love to see you talking about general input esd protection. i know there's a lot to consider, line impedance, capacitance, inductance, response time of involved components (tvs vs zeners), so maybe some kind of hands-on walkthrough of how you personally would approach something like out-of-case interconnection between two boards involving some analog, some digital (serial, maybe rs232 or 485, perhaps i2c or spi) and power lines. I know there are a lot of specialized parts from different manufacturers on the market, but how to choose between them (and are they really needed or can you do similar things with jelly bean components?)
Another interesting topic.
At 12:15 you can see carbon build up on the right jaw where it obviously had sparked before Dave started. Interesting how the smallest gap sparked until it burned further than it's adjacent gap so the nearer points took over till they burned further than the first. Yet the third never engaged - perhaps because it was already toast from previous event.
They should have a substrate or local underlayer that is not carbon based for this...
Great vid! TYVM
Thanks Dave! that was helpful :)
Ummm... better than nothing. I remember a saying about "better than nothing" :p
But that wasn't what I wanted to comment about..
You reminded me about when I was a little kid and I was marveling at the spark gaps wondering what the hell are hose.
They looked like they would make great spark gaps :))
That was very interresting. thx
Very good video- one of your best. When you said you may do a separate video on protection design/consideration and when to use gas discharge tubes vs MOVs vs TSVs etc, Please do. I could never figure out why some designs use one protection scheme vs another. Been a mystery to me.
Neon lamps also come in handy, there are cheap as beans, are a little more controlled, and obviously trigger at a lower voltage, and also they have hysteresis, so after igniting, the voltage can fall down 60V or so and the NE2 lamp stays on in a low resistance state.
Power Max The voltage will fall in any discharge or spark.
0MoTheG Not necessarily. Most real world supplies w/ series resistance will experience a voltage drop, however if you incorporate a feedback loop to maintain voltage at some value and hold it constant, the change in voltage over time will be negligible, and probably not even measurable (at least very difficult).
That feedback would not be hard to do with a large resistor divider and some op amps/comparators.
Good stuff.
With medical devices the main concern is that when a nurse rips the sheet off a bed she can generate over 300kV depending on atmospheric moisture.
At your video, after 2:54, there are few red marked spark gaps. I found that red marked spark gaps (for old telephone company line protection) had radioactive paint on the inner wals of the gap. The one marked black has no such radioactive thing inside, but only red one. Check it if you have chance (GM counter, gamma spectroscopy probe). It is such low activity, that one should be broken to show onto GM counter.
Interesting video Dave. It would be good to find out more about the TVS and GDT devices if you fancied doing a video on them. I was looking into TVS devices recently because I wanted to do an Arduino project in a classic car and read that car 12v power can vary wildly when the ignition is turned off (load dumping).
I was also interested in what happens in a mains surge protector like my Belkin Surgemaster 8 way extension lead. There used to be a huge flash of arcing whenever I plugged in my laptop PSU (maybe inrush current sent to earth?). Eventually, after about a year, there was a massive pop when I plugged the PSU into it and the mains tripped. There was a smell of burning from the Surgemaster but no damage to the laptop PSU, and from that day on there was no more arcing when I plugged in the laptop PSU. I guess the GDT gave up the ghost?
You know you can light a candle with high voltage discharge I took a transformer out of a plasma globe and hooked it up to usb changer 5V 3A and got sparks up to 5 mm away, and if the neutral wire (ground) is touched against the end of the wick snd the placed to spark anywhere else along the wick (yes apparently paraffin is conductive) and with some luck it'll light
When I design a board with these I normally place a small grounded box over the spark gap to prevent noise propagating from it causing issues.
Wow! sacred geometry man!
Didn't he sound like a football announcer during that second spark gap test? 😂
Very interesting! Thanks :)
Thank you
The problem with the spark gaps shown is that the tracking resistance of the PCB is lower than in air and changes over time. Proper gaps have a slot/hole punched between the 2 poles of the spark gap. They still suffer from dust that is drawn into the gap via the electrical field.
Another good video. So now I understand that the spark gap protects inputs/components from over 1500v, but surely they can be killed by less than this. So as protection solutions go, it's like wearing rubber soled shoes to stop you getting struck by lightening. Possibly effective, but no good at protecting yourself from more likely threats.
Right-o Dave, great video/ Things are much more 'spensive, Loosey, in Australia, yeah?
Dave: I need to correct something in this otherwise awesome video. PCB spark gaps SHOULD have a sharp point on the conductors between. The reason is sharp conductors always initiate ionization/arc BEFORE non-pointed conductors. This is the same principle as why sharp metal (Fork) creates a discharge in a microwave whereas spoons do not, or why lightning rods always come to a sharp point. It has to do with the concentration of electrical charge in point conductors. en.wikipedia.org/wiki/Lightning_rod#Rounded_versus_pointed_ends en.wikipedia.org/wiki/Electrical_breakdown#:~:text=Conductors%20that%20have%20sharp%20points,concentrated%20fields%20that%20precipitate%20breakdown.
GREAT video!! Have you done any that involve, mainly, the gas discharge tubes (GDT), or other types of triggering or protection...SIDAC, MOV, transzorb, etc
Thanks Dave!
Is the change in breakdown voltage with the change in altitude the reason some equipment is specified to only operate within certain altitudes? Or are there other reasons as well?
It would be interesting to see how flux left after soldering affects the spark voltage.
It's funny, because I don't really care about content of your videos, google recommended your channel quite a while ago to me and guess what. I tend to come here, listen to you talking for few minutes while you are elaborating something smart about electronics and I just go away after that time. You are strangely appealing though LOL
Really nice understanding given in this video. Thanks Dave. I am little bit worried about aging effect due to environmental effects (Humidity, dust etc) and also due to spark gap, carbonization occur on those exposed patterns and can it affect our product warranty/life cycle? What will be the MTBF analysis for the same?
They used to use neon lamps as spark gaps/surge arresters many years ago
Also, points are best for spark gaps, that's why lightning rods are pointed, the capacitance builds up on the surface area mass, and is concentrated on the point, in fact the GDT's symbol has points, so essentially a neon with pointed electrodes i think.
The pcb spark gap was probably for short static arcs, rather than long duration, so wouldn't have built up so much carbon in a short time
Brilliant
Dave thanks for sharing your rounded spark gap Idea, i really like it and it makes sense to do it that way plus its simple, i am not 100% sure on how this works but Asus "board maker" use an ESD protection on there boards but i believe they use some chip to do it, any idea's of what they could be using as it offers another option.
Cheers!
I fixed regular analog TV's which had PCB spark gaps, typically near the flyback.They appeared to be for short circuit protection safety not ESD protection.
I wonder how much humidity would effect that spark gap.
Wow, my mind is blown. I always thought that the lower the air pressure, the lower conductivity would be, requiring thus greater voltage to produce arcing. Damn you now I must research XD
Think Crooke's tube.
Just like filtering dust or particulate material from water or air (cyclone air filter OZ invention) make it turn for ejection.
Gasses are complete insulators, and compressing more insulating material in a space also compresses the breakdown gradient. Think how oil has higher density and such a high breakdown voltage per mm. It's a similar situation.
To a point. A vacuum is a pretty good insulator, much better than air. But a high pressure insulating gas or liquid is better yet.
hey there dave I do love your content, I was just curious, the program you use for your pcb layout looks really good, what is it? I sure would love to get my hands on it for possible future projects!
It might be less likely to fail from a carbonization-short if it didn't have any PCB material between the 2 points. This could be done with an unplated hole or a notch in the board edge. Although due to machining limitations, the gap might have to be larger, so the breakdown voltage might end up being slightly higher.
I wished they did a little bit of protection in consumer ADSL modems and VoIP Gateways. Almost all phone ports on consumer crap in rural area's dies during a lightning storm. And it's always the phone ports. Ethernet usually survives because of the 1,5kV isolation the HF transformers have. The only place I've seen Ethernet causing problems is with ungrounded electric installations.
I believe the audio issues you were having at the end had to do with the software you were using. Were you recording the audio on the same computer at the same time you were video recording? I noticed that every time you would move or rotate the image on the screen, there would be a popping sound.
Thanks Dave now IED's will be ESD protected...
I'd love to see more videos where you use Altium.... maybe a tips and tricks video?
curtisbeef I back this up too. I love seeing experienced users tell me what they're doing with software like this
curtisbeef I won't do a tutorial video for such an expensive piece of proprietary software. If you can afford $8K+ for Altium, then you don't need a free video from me showing you how to use it.
EEVblog I don't necessarily agree... I mean you do say your vblog is for "electronics engineers" etc..etc.. And its not like paying 8k is the only possible way for someone to be using altium. Students... Employees... Pirates. It is your prefered software package, no? Maybe even just some more videos on general PCB layout best practices and tricks. I enjoyed your other ones. Anyway, keep up the great work I watch all your videos.
curtisbeef Students usually have a lab and training. Employees have employers who can (and should) pay for the Altium training course. And pirates? serious, you are going to argue that?So give me another good reason why I should do an Altium video please...
EEVblog I did give you another reason. More videos on general PCB layout best practices and tricks. Just a suggestion.
Da da da da da da da da da daaaadancing with me ole mate sparky! Oh shit, get the defibrillator ;)
I do like high voltage and arcs of any kind.
You are halfway to making another video on destructive arc tracking. This happens when a current carrying trace fractures or a joint fractures, both cases can be quite.destructive.