| Electronics > Beginners |
| sound analyzer for automating quality checks? |
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| engineheat:
Let's say for a quality check on a gearmotor, you want to check whether everything has been built correctly. If correct, the gearmotor should make a low humming noise, if not, it will make loud noise with a different sound profile. Damaged teeth might cause this for example. The gearbox are coming off an assembly line and currently a person manually check the noise for each unit by turning it on/off. But there is already a station on the line that turns the motor on/off for function test and I wonder if there are sound analyzers that I can put there that can differentiate between a good/bad motor, and then send a signal to the PLC to accept or reject. By the way, there is ambient noise too. What do I need to buy to implement something like this? I'm guessing an industrial PC, a sound analyzer at the minimum. thanks |
| rhb:
Put a piezotransducer on a golden reference and record it. Do an FFT and set up a mask test on the FFT. Schatten sells a guitar transducer which is quite flat up to about 8 KHz for around $20. I'd guess that you can't do a mask test on an FFT on most DSOs, but you should be able to store a reference FFT and do a difference. Problem is, the people who write the FW for DSOs have no idea at all of how to use one. So if you want to plot the hysteresis of a core material you have to buy an ancient LeCroy or build an analog integrator. Cause we just ain't going to let you choose anything but an XY plot of two adjacent raw input channels. The A list OEMs want to sell you another instrument for that. And at $20K for a DSO it's ridiculous that you can't plot CH1 vs Integral(CH2). |
| engineheat:
any other ideas? |
| rhb:
Record 10-20 seconds with a good microphone and sound card to a PC. Decide what you want your resolution bandwidth to be. Break the long trace into pieces of the required length, FFT and sum them frequency by frequency using Octave or MATLAB. Plot it with guard band curves on the PC screen. |
| Brumby:
To get around the majority of the ambient noise, I might suggest you use a contact microphone that can be reliably placed for consistent pickup. An isolation booth would be the preferred option, but I guess that won't be practical. Even so, if it is possible to set up a couple of panels on two or three sides that have sound absorbent material fitted, this can reduce a lot of ambient noise. Once you have the sound collection process sorted, there will need to be some signal analysis with a go/no go output. This is going to be the bigger challenge and the solution will depend on just how precise the analysis will need to be - but the basic spectrum analyser part can be done with a cheap Arduino. The go/no go assessment will require a bit more effort - unless someone has already written some code to do that. Even so, tuning it in for defining the correct pass/fail mask could be fun. Sounds like a fun project, actually. Wish I had the time. |
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