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Is it possible to power a 5v device through a sensor that uses a 3.3v battery? Answered

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This is probably the stupidest question but i'm a total noob at this. I have a sensor which is powered by a small 3v button battery and a small 5v microphone which needs to be connected to the sensor so that the noise data can be transmitted over bluetooth because the sensor has bluetooth. The mic is connected through GPIO pins on the sensor. So I'm wondering if I can power the two together if the only power supply is the 3v button battery and the microphone needs 5v. Also any possibility that I can power the mic through USB?Thanks all.
p.s. Round sensor shown in the picture below is MetawearCPRO, datasheet: https://mbientlab.com/docs/MetaWearCPSv0.5.pdf
ebay link for microphone: http://www.ebay.com.au/itm/172013968121?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

8 Replies

DanzT (author)2017-04-05

Also i forgot to tell you guys, we are making an Android app which can transmit data from the microphone through bluetooth inside the sensor (the round thing from the image above) and it seems like we did the coding right, but the output is always the same, even though the we gave it different noises. So our assumption is that its like that because the voltages are different from each other (too low). So i'm wondering how to get the correct results. I know the coding might be wrong instead of the voltages but we're pretty sure its right.

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Jack A Lopez (author)DanzT2017-04-05

I do not know much about these GPIO pin/ports, but I know that it is necessary to initialize them; i.e. set them up in advance with some kind of command telling what kind of port you want it to be, either digital output, or digital input, or analog input.

I am guessing the API they wrote does this somehow, and the manual for that starts here:


The chapter on GPIO is here:


Also I noticed these people, Mbientlab, they have a forum,


that looks to be inhabited by peoples who actually understand this stuff.

So if you join that forum, maybe people there could help you out, and the fact that your discussions get archived there could maybe help out people in the future with problems similar to yours.

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steveastrouk (author)2017-04-05

It looks to me like you think you can get a analog to digital conversion out of the microphone - you can't. There is an analog output and an output that senses total noise level. The only way to do what you want is to digitise the stream and then transmit that over bluetooth, assuming you have a BT module with a suitable profile on it - you can't transmit sound on a terminal profile module.

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Jack A Lopez (author)2017-04-04

Hey, uh, if this, what you call "5v microphone", if that thing is a module, could you maybe do us a favor and point to a picture of it, or preferably to a product page for it, with some info about it?

Or maybe tell us how many pins it has?

Well, wait, maybe you don't have any docs for it, because you bought it from some dude in an alley, or from some Chinese eBay monger... although usually the Chinese eBay mongers can hook you up with some minimal info, like a wiring diagram, names for the pins, even if they don't have a full blown data sheet in PDF form.

Maybe you could visually pick it out of a lineup? Like, here is a Google(r) Image search for, "5 volt microphone module",


and maybe somewhere in that pile of images, perhaps even somewhere near the top, there is a picture that looks just like your 5 volt microphone module.

Then you could follow that link, and then if you were pretty sure that module is the same as the one you have, then you could share that link with us. Or edit the question you wrote, and put that link in, so that everyone reading this question could get a better mental picture of the particular "5v microphone" you're asking about.

Some of them look like they'll work over a range of supply voltage. Like this one,


I did not actually read the docs for it, aside from the words printed on the module itself, which say, "VCC: 2.4 - 5.5 V"

Actually that suggests another thing to try. Since you have the module in your possession, maybe just connect the terminal labeled +5V, to the positive terminal of your button battery. You know, just pretend like it is a, "3V microphone". Giving it little less voltage than it wants probably won't hurt it.

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DanzT (author)Jack A Lopez2017-04-05

Yeah you're right i bought it from ebay but not from china.

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DanzT (author)2017-04-05

Hey guys thanks for replying. So i uploaded pictures of the microphone (top) and the sensor (middle) to the question so you guys can have a look. The plan is to connect V3v to Vcc, Vgnd to GND and pin 2 to AO, and pin 8 to DO. The sensor (middle) is powered using a 3V button battery (2032). But the spec for the microphone says it is powered using 5v.

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Downunder35m (author)2017-04-04

I take it you use a microphone module?
Capacitive microphones usually come with nothing but the little capsule.
And for those you can look up how to wire and power them.
From there you adjust it accordingly to work with 3V.

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steveastrouk (author)2017-04-04

Without part numbers and a schematic, its impossible to say.

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