EEVblog 1442 - DON'T DO THIS!

hi check out what i found deep in the bunker this is an interesting bit of kit does anyone know what this is mueller beulah bueller it might help if i take this top part here off because this is actually not part of the original product it's actually um like a custom interface for this thing and it's got two really dodgy binding posts here from a company called uh ling dynamic systems uh made in the old dart hi to all my viewers in the old dart um they're not around anymore they were actually uh bought out by uh bruhl and kerr so we just have a look at the top here seems to have like a threaded uh port for like tubing or something like that there's like two acrylic pieces like this and inside seems to be a black disc get it apart and i think i'll be able to show you exactly what this does because at the moment it's not going to do anything now this is actually a bit of kit well not this specific one i used to use these all the time when i worked in the military stuff and also the seismic underwater stuff as well so these were bread and butter and there's only a couple of manufacturers and probably well probably a handful of manufacturers in the world of these sorts of things if we take this off here you can see that this has like a rubber membrane and it actually was attached to this like it was glued down and attached to this at one stage so let me get the rest of the screws out and then i'll show you what this does okay so let's lift this off and when you buy this thing this is how it comes it actually looks like this there's actually it's got screw mounting holes in the side these are just um fillers it's designed to actually uh mount into a big uh huge heavy block like this on like a tilt basis like this in fact they do actually sell uh the bases to go along with these things but uh yeah these are just uh protective caps on there but what this is this is what's called an electrodynamic shaker it's basically a permanent magnet shaker well this particular one the lower end ones like this are permanent magnet shakers so it's basically a big grunty speaker that you attach stuff to and you feed in your signal here and it will have a large amount of movement here and these are as the name suggests electrodynamic shaker it's a vibration shaker motor for testing pcbs and electronics and products and things like these and this is probably the smallest one you'll get on the market this is the runt of the litter i've used ones and here's a photo um like they're the size of a car and they're designed to shake massive products and this is where we would get our products um tested we would like hire the facility uh there used to be a facility out at australian defense industries that saint mary's that i used to go to they actually had uh a one of these gigantic car sized shaker tables and they would take our products in there and we'd you know have to design custom mounts from we'd attach them on there we'd hook up all the accelerometers and we'd actually measure the performance over a vibration envelope to see if our product breaks and designed to simulate transportation by road rail and air and there's various um standards for this that how our products are supposed to survive uh vibration caused by transport of these um different transportation systems so what you'd typically get with these things is like a metal plate it can be like a round or a square metal plate or whatever and uh then you securely mount your product on top you might have to design like little custom clamps or whatever um you want to do to attach it uh securely to the plate so it doesn't rattle around because that's what this is designed to do to give you a precise rattle input a precise vibration input which then transfers onto your pcb and you'll shake your pcb like this and you'd sweep it over frequency usually it's from like you know a couple of hertz up to uh 10 kilohertz something like that and then you shake it in this axis then you mount it again you shake it in this axis and then you mount it again you'd shake it in this axis and you can figure out any vibrational modes on your pcbs if there's any heavy components for example that might actually fall off when the they hit a certain resonant mode because basically every board every mechanical system is ultimately going to have some vibrational mode to it and in tear downs and stuff you've no doubt heard me uh mentioning like uh to20s like this that are what i call flapping around in the breeze they're not actually mounted down now um there's some like a freestanding part like this to220 here this will actually have a resonant mode and if you mount on longer legs it's going to be worse and the more mass it has are the worse it is so you could actually shape this thing and if you get it at a certain frequency and a certain axis these to20s can actually fatigue and break off completely and i've seen this happen on stuff that's just mounted on a trolley in a production facility that's just wheeled around wheeled around by users all day every day and it gets vibration from the trolley and the wheels and the floors and everything else and i've seen to220s completely snap off from such vibrations so this is what these electrodynamic shakers are designed to do they're designed to test your pcbs to make sure you don't have any mechanical problems and it can just be in components it can be joints it can be connectors it can be all sorts of uh stuff it can be the pcb obviously with modern surface mount stuff like this like you've got a lot less mass in surface mount components but you know at a certain vibrational mode you could find like a bga joint could crack under uh there or something like that or even uh one of these connectors like if they didn't have uh the big solder pins on them to actually um anchor them down to the board then these would vibrate right off all these pins in here at a certain frequency and amplitude they would just snap right off and that connector would just fall off the board if you didn't have those big solder anchor points on there to change the physical uh mode of the component so yeah that's what this is designed to do it's basically a electromagnetic speaker hence the electrodynamic uh part of it and this is just going to pop off and it has um unfortunately that won't work why it's broken so there you go oh yeah that star that's all sticky as um yeah that's gonski anyway here we go um inside of it oh yeah okay so that's broken off we have to fix that uh but no workers it's basically just got two wires going into there and this is just a little compliant mount here i'm not sure what the range of this thing is it's probably i don't know if i wouldn't be 10 millimeters it's probably like five zero to five millimeter you can see the coil down in the bottom there there you go it's just poking its head above there but it's basically a giant magnet with a coil it's just a big grunty speaker that's uh designed to be you know fairly linear in operation over its uh range with like a mechanical interface like this because you won't get this with regular speakers with you know your paper or fiberglass cone interfaces so yeah these things are designed so that they actually have mounting points where you can put you know huge metal plates on there and then you attach your products uh to those and the way you analyze the products are that they meet specification is you use um these accelerometers like this now this is a pz pcb piezo electronics one it's one of the big brands in the industry you know you can get uh bruhl and kerr ones as well who now own lin dynamic systems this one's interesting these are actually tiny little accelerometer little low mass accelerometer like this um they you can get them a bit smaller than this but not much you know this is like one of the um real small ones on the market and because then what you'll do you need at least two um usually is you will mount one of them onto the platform so you'll stick it down or either physically mounted or you'll super glue it super glues are very popular for these by the way because they fairly rich amount and then you can snap them off later so you attach one to the plate so then that you can get the response the vibrational response so these are just little accelerometers very linear and they're calibrated and this probably has a calibration sheet it's completely faded anyway yeah you get these calibrated they're really expensive sometimes it's more expensive to calibrate them than it is to buy them but anyway if you take your quantitative measurements uh you know if you're measuring to like a military standard or something like that they will have okay it's got to survive these sort of vibrational modes you need quantitative values but you can use these uncalibrated and still get absolutely fascinating results and see where your uh products actually um like have issues and things like that so anyway you would get one of these you stick one to the plate and then the other channel you would attach to the pcb in a suitable location so you can actually get what's happening on the board as well so you can maybe like if you've got a large board you might like stick it in various locations on the board and you might be able to see the board actually flex like a tiny little board like this you really wouldn't bother but you know a larger pcb that's only mounted on the corners or something or mounted on rails you might put you know the accelerometer in the middle to see what's happening uh to that board flex um like inside a rack uh for example and you might see how that flexes as uh it's being transported so you sweep it right over the frequency range of five hertz to many kilohertz um depending on which uh standard you're looking at and then c if your product a survives b how much flex there is and that has potential uh long-term implications for your product reliability so yeah these are real interesting bits of kit and they're not uh cheap if you have to ask the price um you probably can't afford one brand new and they don't come up very often secondhand oh yeah i really need to really need to fix that that's pretty how you're doing so obviously with this thing somebody has designed a custom interface and it looks like because that was like glued in there i guess they were like using that as some sort of like pump like they've converted it into like you put a tube on here and it just it's a vacuum vibration thing like for a liquid that some say air in the face or something i don't i don't know but um that's the whole point of these things like you just get the motor and you design your own custom like interface for this for whatever need uh you do and they're incredibly versatile you can use them for all sorts of um stuff and yeah obviously i think they've used that for some sort of fluid or air interface thing so that's rather interesting and the matching power amplifiers for these things they can be like insanely expensive and they can have different uh test modes and they can have you know safety features and all sorts of you know limit switches that that tie into them to stop them automatically um yeah because when you get to like the ones that are the size of the car like i've used um like they have a big fence around them and you'll have someone there like as a safety person to make sure you know it's all like everything's safe and you have to get up on the ladder to climb up on the top and then you've got a like big safety interlocks and things to make sure that it's not going to start vibrating and moving when you're actually standing on there wiring up your stuff and things like that and these are usually rated in newton's so yeah i found the data sheet for this this is actually the 200 series but this is like like a really old model but they still actually do uh sell this and as i thought i has a maximum uh displacement of five millimeters it goes to uh 13 kilohertz and it has up to uh 70 newton's um cyan peak range but it actually does go beyond that to 26 uh newton's peak if you abs actually stress it but yeah it's the runt of the litter all right gotta hooked up to the output of a uh yamaha dumpster power amplifier here it's pretty much all i've got um feed the output of the function gently and i've just got like a five hertz at uh half a volt it is a two ohm uh nominal load so i don't know if this yamaha receiver can drive two ohms but you know it's going to be good enough no yeah i could have an input wrong or something put another two ohms uh in series with it so that gives four ohms total just gives a nicer uh load for the amp here i'm pretty sure it can go down to two ohms but meh um so i've now put it on the video ox here so this should work surely oh hey hello she's moving there you go sweet look at that there you go it works a treat bobby dazzler and i can attenuate that by putting weight on it'll have a maximum weight limits only got so many newtons to give that's what she said and of course the volume is going to set the excursion there yeah we can really shake the crap out of stuff now this is great can we go down to 10 hertz there we go 10 cycles per second count them 5 hertz no workers can we go down to one yeah so oh there we go two hertz two hertz can kinda sort of get through you can see the roll off of the amp low frequency roll off of the amplifier here yeah but five hertz can certainly do it but yeah it looks like it's probably got if you go expect check the spec sheet of the amps probably like 10 hertz to you know 20 kilohertz or whatever dude i could play with this all day so this is basically a uh 50 watt air cooled jobby but uh of course once you go up in uh power you can put forced air through them of course and then well the more advanced ones um the power amplifiers and the cooling systems are in gigantic racks taller than i am so yeah serious business but this little one very cute um this is plenty enough for testing pcbs so what i need now is a nice little uh platform that's fun now i know it's a bit how you're doing but uh anyway like this was literally within arm's reach um it was one of these project cases sent into the mailbag had like clear uh perspex on top and then had a uh pcb on there like that and uh yeah we can shake the crap out of that we have a completely offset a table now but you know that allows me to at least uh bodge on a small pcb and we can see if we can do an experiment and break something and you can hear when it bottoms out thank you very much all right so what i've got set up here is an lm7912 voltage rig jelly bean part got it on a little perf board here only got a single screw unfortunately the other screw hole here didn't quite line up couldn't be bothered going out to drill it so yeah it's flapping around in the breeze here and of course this is going to have a mechanical vibrational mode and if we hit the resonant frequency just like that you know the famous uh what is it tacoma narrows bridge or something that actually collapsed um due to the resonant frequency we will find that because we've got a mess up here and we've got a long uh lever essentially all the mechanical engineers are laughing at me but you know anyway it will have a mechanical mode so if we vibration sweep this um we should actually get to a frequency where we actually um see it like really violently kind of shake it you know at one frequency to look like nothing but if we start to hit a resonant mode even in a vertical direction like that i think we're going to start see it really starting to flop around in the breeze and that can fatigue the leads and then break it off um i was going to sweep it but like automatically sweep it uh from like 10 hertz up to a couple hundred hertz but then i thought no let's just manually sweep it to see if we can actually find uh the frequency where it uh gets the heebie jeebies alright so let's switch it on i've got 20 hertz here or increase the amplitude like that and okay i'm going to increase the frequency yeah well that's that's 30 hertz where 10 10 hertz increments probably don't want that we'll go to one hertz increments 30. i want to see this move side to side 54 oh yeah yeah look look 60. 70 85 oh there we go it's 104 hertz oh it's getting more violent check it out 107 hertz 108 hertz oh yeah look at that look at that it's going berko now 110 112 hertz i think we've found its resonant and if i go above that 120 hertz there we go it's gone back so i think we found its resonant point or one of its resonant nodes 110 hertz with a couple of hertz window there about 111 that's a good number 111 hertz so i'm going to leave that there and uh maybe that will eventually fatigue and just simply fall off that's the plan it could be more robust than i think maybe i need to increase the amplitude increase the amplitude till it breaks come on whoa look at that there's a good five six millimeters at least like displacement on that regulator wow still holding in there though can it be fascinating to monitor the output of this like on a scope and see what happens with a vibrational mode on it but anyway that's that's for another video i'm just trying to get this sucker to break but we may not get it with this uh vertical orientation i think we'll eventually get it but um yeah nah we might have to put it horizontal or something like that horizontal like that the poor bastard let's go has that still got the same mode oh yeah yeah she's flapping around in the breeze look at that wow it's got the same sort of displacement that we got before maybe seven millimeter displacement there but it's hanging in there mind you you know those leads are fairly robust but like i said i have seen these no not i've never physically seen it like actually happen live but uh yeah i i have seen products that uh where the to20s have uh snapped off due to fatigue but that's that's pretty impressive that's holding up oh that looks great in slow motion on the gopro [Laughter] that's hilarious come on break your bastard i'll tell you what i'm impressed this must be a genuine national jobby it's not a rip-off just fiddle in with the frequency a bit [Music] well there we go that's 98 yeah it's different here i think i can get a 105 110 yeah it comes straight again at 120 yeah look at 120 there's nothing doing there of course we can mount the board at a different angle but i'm just curious to see if i can get it to go by doing this 95 that's pretty violent around 95 to 98 something like that wow come on i'm gonna experiment i'm gonna go down [Music] whoa well yeah it doesn't like that you should actually hold this sucker down [Music] ah there we go got it got it got it got it got it got it it's going it's going it's gone it's gone it's gone oh a winner winner chicken dinner ah that is fantastic there you go we got it we got one there you go that poor lm7912 oh it's kamagatsa and yeah it's um sheared uh completely off the solder joints there and um you know that was like extreme but you can um i've seen this happen over the span of months so there you go that's an electrodynamic shaker and these are real interesting and useful bits of kit for testing electronics and i've got a nice little beastie here i think it does actually come in a smaller one in this range the 100 series but yeah these go all the way up i'd love to get a bigger one because like you can't use this little one to like shake a multimeter or something like that it's just too high a mass uh it's too big you would definitely need a bigger beastie uh to run that and you know a decent suitable power amplifier but as you saw you know this is like a 50 watt job so yeah just a regular like audio uh power amp does the business there no worries whatsoever like a subwoofer amplifier would uh be the go for like as some of the higher power ones so if you don't want to spend the thousands and thousands of dollars um for the actual real mccoy stuff but yeah um go and try and get a quote for one of these from uh bruhl and kerr now who uh own these and yeah if you have to ask the price you can't afford it their gear is just like ridiculously good quality but you know in the uh military and um like high-end uh fields that i've been in you think nothing of paying like you know five ten thousand dollars for like charge amplifiers for like uh accelerometers uh that we looked at and uh for these uh shakers and the power amplifiers that go with them and the test systems and all that they've got everything you could possibly need i mean they use these things to you know shake satellites and cars and things like that um and it's really fascinating subject so if you want to see me do more videos on this please give it a big thumbs up and leave it in the comments down below what i can actually uh test with this thing but that was a fun experiment we snapped a to20 so let that be a lesson to you don't leave them flapping around in the breeze catch you next time [Music] you

Channel: EEVblog

Views: 124,346

Keywords: eevblog, video, ling, ling dynamic systems, bruel and kjaer, electrodynamic shaker, vibration shaker machine, vibration shaker test, vibration shaker price, vibration shaker system, printed circuit board, pcb vibration testing

Id: 1Y2L6QLOi-c

Length: 23min 57sec (1437 seconds)

Published: Fri Dec 03 2021