I found it in my parts bin.
I can't find anything about it when I Google on the number on the back.
Not visible on the picture but behind the net it looks like a speaker.
Am my assumption that this is a speaker correct?
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Jasen Слава Україні
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Andreas
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3Probably an electret microphone – Oldfart Jul 13 '18 at 08:09
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9... or an ultrasonic transducer, 40kHz, the (R)eceiver optimised one. – Neil_UK Jul 13 '18 at 08:22
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is it like this? https://robu.in/wp-content/uploads/2014/08/hc-sr04_ultrasonic_sensor_distance_measuring_module_1_.jpg – jsotola Jul 13 '18 at 08:34
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@jsotola that looks very similar. But this is only one. – Andreas Jul 13 '18 at 09:40
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It looks to me like a common ultrasound transducer. The "40R" may indicate the intended frequency is 40 kHz, and that this is the receiver, not the transmitter.
I've seen ultrasound transducers that look just like that.
For example, here is a snippet of the datasheet of a SensComp 40LR12 ultrasound receiver:
Olin Lathrop
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Perhaps even this specific one: https://www.microphonestore.co.uk/product/5586329/MZMUST40R/Ultrasonic-ceramic-cartridge-dia-16-mm-x-12-mm ("UST-40R"). – T.J. Crowder Jul 13 '18 at 15:24
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It does seem to be this. But is there any way I can find out what it is? Can I use the multimeter or something? – Andreas Jul 13 '18 at 15:36
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@And: A multimeter won't tell you much. Maybe you can dig around and find which manufacturers print "40R" on the bottom. Otherwise, you just assume the specs of units of similar construction and size will be similar, and get a good idea from looking at a couple of datasheets. – Olin Lathrop Jul 13 '18 at 16:01
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@Andreas have a scope and signal gen? Drive it with sine with a series resistor (perhaps 1k,) then sweep the frequency. Across the device, if you see a dip centered at 40KHz, then it's a typical ultrasonic transducer (seen in burglar alarms and "bat listener" devices.) Also:https://electronics.stackexchange.com/questions/254555/, the T and R have two resonant freqs for different Z at 40KHz – wbeaty Jul 13 '18 at 17:51
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@wbeaty I don't have either of those. But it actually doesn't matter what it is, I was looking for a speaker 8 ohm. I guess I just toss this back in the bin again. I did however find a speaker from an old cell phone, not sure it's 8 ohm though. But I will try it out. The multimeter should be able to measure that right? – Andreas Jul 13 '18 at 18:09
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We'll wait for the next person to find it and post wondering what it is. – AaronLS Jul 13 '18 at 19:52
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It looks to me like a common electret microphone:
https://en.wikipedia.org/wiki/Electret_microphone
You find these in all sorts of toys, phones, appliances, etc. nowadays so I am not surprised that you have one in your bin.
DerStrom8
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