Dynamic balancing with a scope and small speaker
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- čas přidán 16. 06. 2022
- Using a small loudspeaker as a transducer to pick up vibrations from a spinnint rotor and measuring those with an oscilloscope. This allows me to quantify the vibration for doing dynamic balancing.
This whole method to have something to try to balance the vibrations of then new shelix cutter head on my jointer.
I’m a vibration analyst by trade and your method is spot on! The only additional thing we do with the “test” weight information is build a vector diagram on a polar plot to determine where the optimal final weight should be located. Then there is some math to determine the weight amount but that’s just some simple cross multiplication. Doing this all with a speaker and o’scope is just downright genius.
Spot on, search for graphic balancing method. You can solve your needed weight and place by doing 3 runs while moving the test weight in 120° increments around. The place your three influence circles meet gives you both the place and amount of correction weight.
Using a speaker as a velocimeter is genius!
Search for this on CZcams:
3 point balancing method
What is your preferred method to apply an encoder? Or does it even matter?
@@brad3378 for the 3point Methode, you don't need the phase angle, for vector Methode the phase angle of the vibration is needed that way you only need to do a single test run with a test weight to get the correction weight and position. Getting the phase angle or a reference is done by a keyphasor, or a laser module that detects a ref mark. As a DIY solution you would need anything that gives you a signal on the scope exactly once per rev, always at the same point.
Cross multiplication, is that the one listed by the same name on Wikipedia (I was initially assuming the cross product instead)?
This is a pretty clever method! Thanks for sharing with us.
Really interesting to see a speaker used that way. All you need is a sufficiently capable rotary encoder for position tracking and you've nearly caught up to industrial impeller balancing systems.
It is! I guess you could use a voltmeter instead of a graph, but it would take more patience.
I think he wouldn't even need a rotary encoder.
a simple photo diode to measure a fixed point per revolution should be sufficient for home application.
With a dual Chanel scope he could overlay speaker and "zero point" and from there calculate the angle where mass needs to be taken off.
@@fabianrudzewski9027 A simple 5v hall effect sensor would also be a good choice when working with metal objects.
phase of output signal from speaker is a non linear function of frequency, it can be compensated but it's not linear
There are solutions that don't need to know position. Some Balance Technologies machines just have a strobe light so you can point it at the rotating object and it will freeze the point where weight needs to be added or removed. And with the amplitude of the vibrations you can set the correction radius and readout the grams required. This was all old school analog circuitry, too.
Mind blown. It would never occur to me that there was an issue, let alone following such a logical approach to fixing it.
I confused dynamic with active. I thought you were going to feed back the vibration into the weighted voice coil to damp them that way (with destructive interference). Your way makes way more sense. Particularly for the heavy cutter. Looking forward to the conclusion!
Yhea. That is how I interpreted the descripton.
That would be really freakin cool. Like an engine with a software ballance shaft.
With two speakers configured orthogonally and two channels on an oscilloscope, Lissajous curve could be displayed. You could directly find the vibration vector. If you further know the phase of the motor, you could even calculate and display the exact angle at which you should add or remove weight.
Wow Matthias! You never cease to amaze me! The way you combine intuitive understanding with real-world electronic know-how is clever and clear. When I was a kid and built slot-car motors, (circa 1964) I just chucked the armature into a drill, spun it, and lightly touched it with a magic marker. Then wherever the marks were thickest, I drilled a small hole in the armature; Reversed the armature, and did the same thing from the other side. That was as close to dynamic balancing as a cash-strapped kid could get, But it worked.! Of course I didn't have access to these electronic measuring devices then, so that method was a tedious iterative process. Even now, I would have never thought of using a speaker to generate a readable pulse into an oscilloscope. Brilliant idea!
I love the low cost approach to everything you share. It is so refreshing in a world of "Look at all this cool stuff I got for free to show you, please go buy it".
That impresses me the most in your videos is the didacts you have. Even when I know nothing about what you are experimenting with I'm always able to understand the concept.
You would be a perfect college professor, for sure!
You could possibly get similar results using a 'vibration meter' app on your phone (for those of us without an oscilloscope).
I dynamically balanced the drive pulley on my metal lathe by taping an old phone to the headstock and measuring the vibrations.
Me too, but I want an oscilloscope, its probably much more accurate. Vibration analyzers at mm/s^2 range are very expensive as well 😢. I balanced my angle grinder with my phone lol this is amazing.
If you have a small mirror and a laser pointer laying around, you could probably do this completely analog. Put a piece of paper on a wall far away to mark out the sweep of the laser. The added benefit is electrical noise would have no effect.
Mirrors have mass
I use this method to dynamically balance props on drones.
@@MadScientist267 The mirror goes on the static part so makes very little difference.
That's freaking cool
@@DullPoints I have a really old vid on my channel if you want to see how it's done. 🙂
Wow, get this circulating around the shade tree, DIY engine builder community for balancing crankshafts. Very impressed by your ingenuity. Thanks for posting!
I never knew how balancing could be done before this. Fascinating video.
Wow, I'm blown away by the analysis and the use of the speaker is ingenious. Thank you for the video.
This is quality content.
I like it a lot.
Balancing fans and rotating things with a cheap diy friendly way and increasing their lifespan, lowering the noise and vibration is a really good thing.
The earlier video you had with balancing a fan really helped me right after i bought a box fan (brand new) it wash shaking violently and dancing over the floor, but after a few minutws balancing it it became very silent and no noticeable vibration
My God, dude. Your methods are simply inspired! What an awesome approach. I've yet to see a video from you where I did not learn something. Bloody brilliant.
Very impressed with everything you do. Thanks for sharing.
Man! That was a super cool video! I am astonished by your method, as always. I dream of being "your kind of smart" but the truth is, I'm a little lazy about trying to be. However! You explain the details so perfectly that I sit here and think to myself "That makes total sense. Of Course that's how that works!". I truly do understand and follow your explanations. I just, would never have gotten there myself. "That" is what perplexes me sometimes. That's the fun in it all... Right?! I have thoroughly enjoyed every one of your experiments over the years. The mice experiments were lots of fun! I appreciate your dedication to not only the true and sometimes brutally honest results but also to the storytelling arc. Thank you.
Absolutely the best video i have seen in the past thousands
This is fascinating. Definitely beyond the scope of any of my projects but it's interesting to read all the comments from all these knowledgeable viewers.
Have you thought about marking a zero position with reflective tape and use an optical pick up to mark the zero position on your oscilloscope? That would make finding the “location” of the imbalance easier than trial and error.
Once you figure out the delays from vibration to the speaker pickup, however adding a weight should show that easily enough.
This looks like a job for a piezo transducer! Also thanks for the demo. I am about to buy one of those blowers and this will help a lot if it's unbalanced.
Very cool. You never cease to impress, Matthias.
Thank you very much for this very interesting video on DIY balancing.
I'm very excited to see the process done with your planer!
Fascinating approach to dynamic balancing! Cant wait to see the Shelix cutter head balancing :-)
*checks notes* Dynamic Systems Laboratory, Junior year! Super clever implementation of the 'accelerometer!' love your videos, WoodGear.
Nice and simple approach to solving this complex problem. I like how you use a speaker instead of a fancy pant accelerometer.
I proposed a system like this for using a speaker and diaphragm weight to dynamically balance motors about 20 years back on the electronics forums.
The one thing you missed which would have been an improvment would be to place the whole assembly on an elastic suspension, which could have been as simple as a springy foam block. Your setup was damping the vibration into the table which reduced the measurement amplitude and accuracy.
Very cool project! 👍
I have some 3D-printed flywheels on small RC brushless motors that I need to balance, and this method looks like it would be ideal and uses stuff I already have on hand. Thanks for the tip!
Fantastic idea without expensive equipment, love it!
That is a pretty cool idea. I really appreciate your sharing that.
Amazing! Anyday I will try to use this method!
Fine work by you and exposition for us.
Now THAT is really neat. Thanks for sharing.
Matthias blows my mind every time I watch one of his videos.
Wow!! I never would have thought to check the balance of these things. Makes perfect sense though! I love these videos!
👏👏
it was close enough for using already. I just wanted to see if my method works.
That's just brilliant diy!
On the driven end of the rotor I believe you were seeing a central frequency of 60hz and sidebands each side, offset by 10hz. I suspect it was caused by geometrical angular/offset misalignment between the motor and fan rotors if they are rigidly coupled together. Very smart use of the speaker to measure the waveform!
I could watch this a billion times and still have no idea how you did that.
Oh my, that’s smart! Thanks for sharing!
This is excellent to see, really cool!
Super fantastic! Thank You!
I'm excited for the followup!
You are a genius gentleman!
With this technique, you have to make sure the resonant frequency of the speaker is not the same as the DUT.
Otherwise the vibrations will look a lot stronger than really is.
I'd imagine a speaker having very little resonance (given their purpose)
But, doesn't it change that, if you add weights to the diaphragm?
@@AmirASD The more mass, the more inertia, the lower the frequency of resonance.
Same thing with inductance. The more henrys, the lower the resonant frequency.
I suspect that adding an electrical load on the speaker (perhaps a resistor equal to the speaker's nominal impedance) would damp any resonance.
Does it really matter? The frequency response will be nonlinear but we only care about relative changes. As long as the DUT frequency remains constant I think it would still work fine.
A guy at work once had a fan very similar to that where a blade had busted off and was no where to be found. He was trying very hard to fabricated a thin blade to replace it when I suggested we just count how many blades there were and snap one off from the opposite side. We counted and it was all good and snapped the opposing right off and it ran sweet.
Very clever! I imagine that squirrel cage fans are pretty tolerant of imbalances given that they all collect dust, and any dust buildup will likely throw off even the most carefully balanced fan. However, a balanced fan will give off less fan noise and that's always a blessing. Good show on the use of low cost test gear to analyze a problem!
The dust will be evenly distributed around the evenly sized and evenly spaced blades of a squirrel cage fan, so it doesn't affect the balance much. Initial balancing really protects the machinery and makes it last longer. There are industrial balancers that balance absolutely everything in, for example, a pulp mill. I once pulled a single leaf out of an automobile's squirrel cage blower that was making a horrible noise and that fixed it perfectly.
I tried with a piezo speaker and some weight glued to it. Worked great also for high frequency vibrations.
This is pure gold!
WOW!!! Way cool. Get HOT on balancing that shaper/planer! Im very interested! Looks like a very cool project!
That's an awesome method!
A simple practical demonstration like this is great for a lay person like myself
That's a pertty interesting idea to use a speaker as an accelerometer. Ive seen them used as microphones, but never for low frequency. It's not a calibrated measurement, but for some quantitative analysis it's more than good enough.
Very interesting topic and clever idea of using a speaker. Nerdy stuff as usual ;)
my father has a balancing machine for big rollers and ducts. Althought its a little bit more sophisticated with a control computer etc., it messures the vibration on both sides of the tube (its laying there on bearings) and always knows at what position the duct is with the help of a light sensor and a glued on tag, after you run it it tells you the spots that need weight automatically.
Clever guy, another great video
That's a brilliant idea , seat of your pants engineering . Food for thought , thanks for posting the vid.
in the 1980s the company I worked for looked at analysing vibration from the heavy industrial machinery it made in an attempt to give the operator maintenance information much earlier than his ears could detect. It actually worked quite well but few end users would pay a worthwhile price for it.
There's a mentality of "don't fix what isn't broken", which seems to stop them from considering that "Everything is gradually breaking, so it WILL break at some point. Fix it when it's most effective to do so".
I've worked with a number of factories and suggested that premise as well. Advising that a lot of their stoppages and repair costs could be reduced, AND would offset the cost of any system upgrades by an order of magnitude. Not a single one was willing pay for it except where I just did it anyway, and demonstrated it, and billed them.
Really cool and interesting video!
Can't wait for part 2!!
Excellent! Thanks for sharing man!
Clever boots. I look forward to the joiner balancing video.
Thank you for this idea.
Very interesting! I'm thinking of combining this to Denis' approach (channel "the GADGETS playlist") to dynamic balancing, ie, using a microphone (or speaker) to listen to the vibrations and reference it using a photocell to figure out where the weight should go - and perhaps combine it with the Y approach, ie, instead of adding weight at position 0, add it (for instance) at positions -3 and +3.
Denis uses an accelerometer to measure the vibrations, not sure which option would be more accurate.
That's cool, would like to see further improvements on this concept.
i might actually use this method. ive made fans and fast rotation devices before and many times simple field balancing techniques will not suffice. it also shows the thousands of uses for signal analyzation of electro-mechanical components using an oscilloscope.
I would love to see your take on the DML speakers.
Thanks for this, quite interesting.
30 years ago we use to characterize disk drive motor samples with a similar set up sensitive and expensive B&K gear. Today, you can pull the 9 axis of freedom board off your drone and couple that with your favorite eval board (pi, arduino, stm32) and throw together a pretty darn good sensor system. Couple that with all the free firmware that deals with static and dynamic behavior and you will know more about anything you want to measure. The vibrations in the handle of your weed eater, lawn mower, shovel, hammer or vibrations in the motors... you could spend your whole summer on this..
KWR, Clifton Precision?
Brilliant, Matthias! 😃
Looking forward to see the process on the jointer!
Stay safe there with your family! 🖖😊
Very informative video 👌👌
With the addition of either an optical sensor tach, on the scope, the phase of the vibration relative to the shaft position, can be used to find the offset and amplitude of the balance for accurately finding the weight and position for the correction. This is how a tire shop wheel balancer works.
I don’t always get what you’re actually doing but it always looks so cool
Fascinating stuff.
Beautiful and insightful work, congratulations!
The 69-ish Hz you described at timestamp 5:08 is possibly due to the aliasing between the 60Hz network frequency and the 50-ish Hz of the rotational speed.
The aliasing or beating frequency generates a pair of side bands (+10 and -10 Hz)
The 10Hz can be also observed at the 10Hz region of the spectra and as a sideband of every 60Hz harmonics.
If the system responds well to higher frequencies, you may also find a series of 100-110-120-130 -140Hz and so on.
this is also what creates the really cool "whirr" sound when induction motors start up!
@@polymetric2614 , the “whirr” is outstanding when you change speeds of a 2/4 poles motor 😊😊
Promising hypothesis !
You made an electronic stethoscope to diagnose an illness with that fan :-) nice work.
Imterestimg video. In the past I've wondered if there's some way to balance a ceiling fan besides by trial and error. I have to believe this approach could be adapted for that.
Brilliant. Thank you.
This should be on your main channel. Clever idea.
it's not woodworking by any stretch
@@matthiasrandomstuff2221 Just add a few shots making the bracket et viola! Great video, thanks.
Thank you so much for this. So well explained and demonstrated. The only thing I'd like more information on is the weights added to the speaker. How much? The purpose? Etc.
Very very cool way!
You are a genius 👏. Other method may be using a high speed MEMS acelerometer (1 khz or more) with an esp32 or Stm or RPiPico.
That was intense
Clever, thank you.
That is so cool!
Interesting stuff. I always wondered how wheel ballancing machine got thier data. And crank shaft ballancers.
Like others have said, quite clever using a weighted speaker as a contact mic, but I was expecting something like noise-cancelling headphone technology, where a vibrating mass cancels out the vibration of the tool in real-time 😄
nice idea to try and error with pulsing at the same frequency that the imbalance vibration, delay represent angle of rotor and amplitude power in speaker represent a easy variable weight! thks man
@@sebastienl2140 probably you need a tach pulse to timely find the high vibration spot then feed a cancelling waveform with the speaker exactly opposite phase
So about the 120Hz humming:
A transformer iron core expands and shrings with the magnetic forces involved. An electric sinus signal means a plus and another negative wave or going from 0 to max to 0 to min and back to 0. So that's why a transformer core hums with double the frqeuency of the electric signal.
In most (if not all) parts of Europe it's a 100Hz humming, because we use 50Hz electrically.
Super idea !!
Very good 👍
I would give this a try with a piezo transducer.
You may want to check over by the motor with the fan stalled to see if you are picking up magnetic hum from the motor windings. Also the speaker probably only outputs vibration that coincides with the line of the voice coil movement. Nice experiment and thanks very much !!
that's what I was demonstrating in the video
cant wait to see you balance moore stuff
thanks for explaining what dynamic balancing entails. Now i'm curious: it's possible that dynamic balancing can throw off static balancing? Also: i read on their brochures how some bandsaw manufacturers balance their wheels both statically and dynamically; would it be worthwile trying that on one of your bandsaws?
I have an old computerized tire balancer that works in a similar fashion. However, it first calculates static balance using a tachometer. With a horizontal axis, the wheel will accelerate when the heavy side is turning down, and decelerate when it is on the up.
Back to your device, you could improve your trial and error approach by connecting the vibration trace with something that correlates to the phase of the wheel. I would suggest putting on a strip of reflective tape and using a laser and photoresistor to pick that up as a second trace on your scope.
yes, I keep getting this comment over and over. I didn't do it, not becasue I didn't think of it, but because it wasn't worth the development effort for what I wanted to accomplish.
Creative thinking.
Mind blown. How do I always end up learning something in every one of your videos?
Good video I did this users ago on a paper shredder
if it comes to balancing the blade thing you probably will either have to balance it every time you replace a bit but you could probably do it with different length screws because i doubt you can shim it