Need vibration 24/7 for a few weeks without breaking - Page 1
Forum section: electronics / beginners

author: mortrek
author_rank: Contributor
timestamp: June 23, 2019, 06:40:31 pm
content: I'm trying to do an experiment that requires a vibration motor / some way to vibrate a container at a fairly high frequency, but I need it to run for weeks or more, preferably 24/7 but possibly on a timer. I'm also trying to do it as cheaply as possible.I tried some cheapo Chinese coin cell vibration motors running 24/7 and they lasted 2-3 days and then broke. The container that I'm vibrating can be fairly small, and the frequency is not extremely important, but a bit lower is better. The motors I had are something like 10k RPM, but a few thousand RPM would be good if possible. I just need them to be reasonably powerful, but that being said, the cheap coin cell ~40mA motors were probably strong enough.I've considered the more expensive brushless name-brand motors, like Jinlong W0934AB001G, but those still are only rated to maybe last a week or two of continuous use (I'm extrapolating the ratings, since they are based on pulsing on and off). I could time the vibration, running it for a few seconds, then off for like 30, something like that, but I was hoping to use some easy thing I could just drop in and it would work. I have a feeling that I'd need to break out an MCU or 555 with a transistor to get the needed current, or something like that, to make that happen.I've also considered using a speaker to vibrate it from the bottom, but I'm not sure how to best approach that option. A super cheap frequency gen + cheap amplifier + cheap speaker might work.Everything I can come up with is a bit of a cludge but I'm not sure if there is any obvious and simple and cheap solution that I'm missing.Thank you ahead of time for any guidance or tips.

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 23, 2019, 06:44:36 pm
content: Quote from: mortrek on June 23, 2019, 06:40:31 pmTake a motor, put an offset weight on the shaft, and attach the motor to a plate which is attached to your container. Speed of motor = frequency of vibrations, mass of weight and distance of weight from shaft set amplitude of vibrations.

author: mortrek
author_rank: Contributor
timestamp: June 23, 2019, 06:47:41 pm
content: Will that work long-term though? A normal motor isn't meant to have that kind of force on its shaft right? I'd worry that it'd break, and I'm not sure what sort of weight to use that wouldn't eventually break off or something. I can get a standard larger vibration motor I suppose.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 23, 2019, 06:53:44 pm
content: Not large is relative. It really depends on the weight of the box to shake an how much vibration is needed.A reasonably large an robust motor with a little unbalance it one option. If not too much unbalance it can run for quite some time (e.g.. months).If it's powerful enough the speaker and amplifier way can work too. It may help if the frequency is at a resonance as much lower power is needed in this case.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 23, 2019, 06:57:44 pm
content: Without knowing details on the weight, frequency and displacement, it's hard to say. I was attempting to run some simple vibration tests at home. Maybe this will give you some ideas.https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2292114/#msg2292114

author: mortrek
author_rank: Contributor
timestamp: June 23, 2019, 06:58:43 pm
content: You're right, it's maybe 3 inches tall and 2 inches wide, and made of glass.I looked at a bit larger name-brand motors that have nominal 6k-8k RPM and they still are rated at 96 hours with 2:1 second pulses. But maybe I should just go with the speaker idea if you think that'd work.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 23, 2019, 07:22:53 pm
content: QuoteHard to say without knowing the weight, frequency and displacement you are needing. They do make some pretty impressive speakers. The problem is they don't provide a lot of details on them.

author: GerryR
author_rank: Frequent Contributor
timestamp: June 23, 2019, 07:40:49 pm
content: Go here:https://www.mcmaster.com/vibratorsThese are intended for industrial applications. The air powered units can get you into the high frequency range, if you have an air compressor. The motorized ones are not as high in frequency but can handle some pretty good loads. Hope this helps.

author: mortrek
author_rank: Contributor
timestamp: June 23, 2019, 07:41:57 pm
content: I've decided to try an old 3" loudspeaker I have lying around and my lab function generator, plus I ordered a cheap LM386 board. I'll see how much vibration I can get out of it. If it works well, I'll consider buying one of those $8 square wave gens so I'm not using up my function gen.I need very little actual displacement (<1mm probably), not sure exactly about weight (<1/2 pound). The coin cell vibration motors may have been strong enough if they had lasted longer. Now that I really think about it, the nice thing about the speaker setup is that I can easily change the frequency and 'intensity'/displacement in the future, which I may need to do to reach an optimal setup.Thank you everyone.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 23, 2019, 08:05:29 pm
content: You may want to just use a power supply to drive the speaker coil to see what sort of lift and travel you can get out of it.The speakers I tried have VERY POOR frequency response. The only way to really tame it was to use feedback. If you plan to just run it at some frequency, it may not be a problem but you may still need a way to measure the travel.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 23, 2019, 08:23:55 pm
content: 1 mm displacement is already a lot for a 500 g sample. The speaker would get that much only in resonance. Mechanical resonances tend to be relatively high Q (typical Q is more like 100-1000) and can thus give a significant larger vibration.1 mm displacement at audio frequency gives a hell lot of acceleration !I did that once with a resonant system - but this was one with exceptional low damping and a very small system, so that very little power was sufficient.The motor with imbalance usually gives a 2 D movement, not just linear.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 24, 2019, 03:40:26 pm
content: Quote from: mortrek on June 23, 2019, 07:41:57 pmQuote from: Kleinstein on June 23, 2019, 08:23:55 pm0.5lbs would be about 250g. With my four cheap speaker setup with DC applied, it will lift the weight of the table along with 200grams about +5mm. Of course it can also lower the table. The weight will add an offset to the position but again, it's a closed loop system using position feedback. I suspect the drivers the kids use in their cars would easily lift this amount of weight at DC.A friend of mind gave me a much larger driver that was used to get the base for their home stereo. I played around with it a bit and it appears it would easily out perform my current setup.OP will just need to experiment with it to see if it can work for their application. The following paper may be helpful.https://pdfs.semanticscholar.org/ae56/0d0290985ec64fb901c3cdb5970c17d52514.pdf

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 24, 2019, 03:52:47 pm
content: Industrial vibrators are often run on air. It's a circular track with a ball bearing circling around due to a jet of pressurized air. Not much to break, very reliable and probably overkill for your situation but maybe it can serve as an inspiration. Below is another example with an offset weight in a wheel.

author: bsudbrink
author_rank: Frequent Contributor
timestamp: June 24, 2019, 03:58:10 pm
content: Try googling for "shake table". You will come up with a bunch of industrial hits as well as a fair number of DIY pages. I don't know about "weeks", but the shake table we have at my work runs for days at a time when they're testing packaging for a new product.

author: shanezampire
author_rank: Contributor
timestamp: June 24, 2019, 05:09:57 pm
content: I had one them old sanders you attached the sandpaper to. The pad was broken and you couldn't attach sandpaper to it no more. I attacked the plastic lid from a jar to it with screws. I put my small engine carburetors and cleaner in the jar, screwed it to the lid, and turn it on for a few hours. It vibrated them very well. It was a Black & Decker Mouse Sander/Polisher/Detailer if you want to see which one I used.

author: Gyro
author_rank: Super Contributor
timestamp: June 24, 2019, 05:22:23 pm
content: You could try a 'Bass Shaker'. They're designed to make your furniture shake in response to 'subwoofer moments' in films.You might get better efficiency than with a standard speaker, at least around resonance....https://cpc.farnell.com/visaton/bs130-4ohm/bass-shaker-4-ohm/dp/LS04225?ost=shaker&krypto=sAcEhSN53rTcgNyJqND2IvBr5vor3JSMJ3zz2%2BDbi2MXlKKg5kraAg9QasXDMNrHajc%2BV%2FQXF9jlQcZ3oTpHKQ%3D%3D&ddkey=https%3Aen-CPC%2FCPC_United_Kingdom%2Fsearch

author: Kleinstein
author_rank: Super Contributor
timestamp: June 24, 2019, 06:21:09 pm
content: Quote from: shanezampire on June 24, 2019, 05:09:57 pmThose sanders may last a week (some 168 hours) or so. The normal life of carbon brushes found in the usual motors it at some 300 hours and not all those sanders get to the point of changing the brushes before the bearings break down. It may be slightly better when shaking as there is less dust.

author: David Hess
author_rank: Super Contributor
timestamp: June 24, 2019, 07:00:11 pm
content: Another way which lasts longer than putting a weight on the motor shaft is drilling some material out of the rotor inside the motor so the motor bearings carry the unbalanced load evenly. This is easy to do with inexpensive shaded pole AC motors and being inexpensive, replacement costs are low.

author: jmelson
author_rank: Super Contributor
timestamp: June 24, 2019, 08:17:17 pm
content: Quote from: cur8xgo on June 23, 2019, 06:44:36 pmRight, our shop has a vibratory polisher. It has a container on top, and a rubber-supported plate on the bottom with exactly this sort of setup attached to the plate. I know our shop has let the thing run overnight polishing some parts. It gives a pretty hefty vibration, too, that jumbles parts and ceramic polishing stones with a little "soup".Similar devices are used in the gem, mineral and jewelry trades.Jon

author: Rick Law
author_rank: Super Contributor
timestamp: June 24, 2019, 08:22:53 pm
content: You can also consider using an MCU to control a few vibrators to spread the duty around. So, (let say you have just 4), the MCU will let #1 work for a while (say 10 minutes), then it switch on #2 and let #1,3, and 4 rest. So on. By spreading the actual work time to multiple vibrators, it should make make the whole set up last longer. If you want to be fancy about it, you can even add vibrator-failure detection and skip the failed one plus generate an alarm letting you know on has failed. With that, you know as long as one vibrator is still working, the darn thing is still vibrating. Now you can implement "hot swap" like they are hard disk RAIDs.Even if you use something as simple as the Arduino NANO as the controller, it can control >6 vibrators easy. It wont put out your 40mA, you need to add a switch be it a relay, transistor or whatever for that vibrator-driving current. But, the Nano can do the control functions for half a dozen "coin vibrators" easy.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 25, 2019, 05:47:04 am
content: Back in the day, when I worked at a TV Studio, we had a very small Sony picture monitor which spent its life in the instrument panel of the station chopper.It was for programme video, not part of the instrumentation, so didn't have to be "aviation rated".As things happen, the tiny trinitron lost emission, so was replaced.That was where the trouble started!On refitting the monitor, it failed after a week, so it was pulled out & fixed.Next try, we got a day.Eventually we got it to be reliable by liberally coating the board & wiiring with "Silastic".Over that time, we referred to the helicopter as "our multi-million dollar vibration test bench".So there you are---- just fly your device around in a helicopter!

author: Jeroen3
author_rank: Super Contributor
timestamp: June 25, 2019, 12:33:03 pm
content: The "official" way it a large surface transducer, a big coil and a large amplifier rack to shake whatever you bolt to it.You can buy surface transducers onaliexpress. And pull some audio amplifier from somewhere else. With those I think you can get at least somewhere close to what resembles an "official" shock table.If you can get away with the heat you might even have success with a lock solenoid.

author: jmelson
author_rank: Super Contributor
timestamp: June 25, 2019, 09:40:32 pm
content: Harbor Freight has a $55 "5 Lb. Metal Vibratory Tumbler Bowl" that ought to do what you need. Maybe it will provide MORE vibration than you want, but sure worth a look.https://www.harborfreight.com/5-lb-metal-vibrator-tumbler-67617.htmlJon

author: windsmurf
author_rank: Frequent Contributor
timestamp: June 25, 2019, 09:53:35 pm
content: Quote from: jmelson on June 25, 2019, 09:40:32 pmI don't think that'll create vibrations in the kilohertz range which the OP said he wants...

author: joeqsmith
author_rank: Super Contributor
timestamp: June 26, 2019, 12:20:05 am
content: Quote from: windsmurf on June 25, 2019, 09:53:35 pmQuoteI was thinking from their original post, the motors were just an offset weight. 10K RPM or 167RPS, so something under 167Hz was all they were looking for.I hadn't thought about them trying to make a parts cleaner or a mixer. I just assumed they were trying to do some sort of basic vibration testing.

author: windsmurf
author_rank: Frequent Contributor
timestamp: June 26, 2019, 03:41:51 am
content: Quote from: joeqsmith on June 26, 2019, 12:20:05 amYou're right I misread the OP statement as 10Khz....

author: Synthtech
author_rank: Regular Contributor
timestamp: June 26, 2019, 06:14:59 am
content: Go to a drum shop and buy a seat shaker. It’s a subwoofer with a weight instead of a diaphragm that drummers bolt under the seat of their drum stool and they use an audio power amp to feed the kick drum microphone signal into it to give them the feeling of the kick drum thumping their butt. Feed whichever frequency you want in there up to the maximum that it will handle.