New part/module to test
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So I found this speaker module that I salvaged from an old Dell computer that looks a bit interesting. It appears to take a 5V power input and an audio signal and runs the small speaker with a built in amplifier. The diameter of the speaker is about 31mm and the whole module with the tab is about 44.45mm. The number on the chip is 4871 and appears to be a national semiconductor chip. When I looked that number up for NS, The only thing I found was an LM4871 which I am assuming is the chip as it is a 3W audio power amplifier.
Seems like it would be a good little module to use for some kind of audio alert/alarm for a project.
It has 4 wires to it with 4 connections labeled on the board. There are the obvious P5V_IN, GND and AUD MONO. Which I assume are 5 volt power, ground and mono audio in respectively. I am not sure what SPK DET would be though. Does anyone have any ideas?
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I’m pretty sure the SPK DET lead allows the computer to know if there’s a speaker in place; my VOM shows it tied to ground.
According to https://www.contrapositivediary.com/?p=1758
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@mfalkvidd Great info. Thanks.
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Interesting, they run from 2V, need only a few external component and and they cost peanuts on AliExpress, I'm buying 10 right now for testing with the speakers salvaged from my children toys.
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@nca78 i assume you are talking about the amp chip. I think they are similar to the LM386. Sounds like they have a lower input voltage range.
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@dbemowsk said in New part/module to test:
@nca78 i assume you are talking about the amp chip.
Yes of course. I don't thing they are many speakers+PCB available on the market, maybe in the US but not here at least
It looks pretty simple to use so it's not a problem to go with the chip.
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@nca78 said in New part/module to test:
It looks pretty simple to use
Getting sound out of an amplifier is pretty easy... but to get a good sound and filter all noise is harder, especially if you are going to use this near any RF signals or power supply. But you probably know this already...
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@sundberg84 said in New part/module to test:
@nca78 said in New part/module to test:
It looks pretty simple to use
Getting sound out of an amplifier is pretty easy... but to get a good sound and filter all noise is harder, especially if you are going to use this near any RF signals or power supply. But you probably know this already...
I never did anything related to audio, it's not in my plans yet, but I'm looking for (it seems) something similar to what @dbemowsk says: make a loud noise/audible alarm and with only a handfull of parts. For that no need to worry too much about noise or distortion, I'm not planning to use it for music.
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@nca78 - sounds like a cool project. You will be able to amplify a analog signal using these chip like x100 (the more you amplify the more noice-killers you need) but even this will not be enough to make it very loud. Now, I dont know how "loud" you will need the alarm to be but most likely you need a more powerful amplifier for a household-alarm type of dB.
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@sundberg84 said in New part/module to test:
@nca78 - sounds like a cool project. You will be able to amplify a analog signal using these chips from a couple of mV to like x100 (the more you amplify the more noice-killers you need) but even this will not be enough to make it very loud. Now, I dont know how "loud" you will need the alarm to be but most likely you need a more powerful amplifier for a household-alarm type of dB.
Haha no, it's not for a home alarm but as an alarm for a sensor, possibly battery powered. Just need to be loud enough to be heard, but no need to pierce anyone's ear drums
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@nca78 Ahhh
- the I think you will do just fine 
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@sundberg84 not looking to do hi-fi sound, mainly to amplify an alarm or something simple.
