4 ms·
PoE works better (cheaper, higher bandwidth, differential signalling for higher EMI resistance, readily shared, etc.). Plastic covers are ~free (splash out and
by contingencies 2y ago
PoE works better (cheaper, higher bandwidth, differential signalling for higher EMI resistance, readily shared, etc.). Plastic covers are ~free (splash out and deploy duct tape if necessary). MEMS mic -> I2C -> cheap MCU -> ethernet. Theory: Capture digitally, and send the data - forget XLR and other expensive analog 'professional' fancabulation[0]. [0] https://www.youtube.com/watch?v=Ac7G7xOG2Ag https://www.youtube.com/watch?v=Ac7G7xOG2Ag
- jononor 2y agoI think you mean I2S (or PDM)? I2C is not common on MEMS microphones, as the bandwidth is generally insufficient for audio signals.
- contingencies 2y agoRight, I don't usually touch audio or video applications.
- hcfman 2y agoPOE very easily tends to inject noise into microphone inputs. If you run a Raspberry Pi for example with POE you get that. This can be fixed by using a power conditioning hat and a POE splitter but now the costs are really increasing. But it works.
- 15155 2y agoGalvanically isolate the ~100mA of supply current you need - the Ethernet interface is already isolated.
- hcfman 2y agoI’m pretty sure that Raspberry pi’s draw more than that. But if you have a good way to fix this I’d like to know. The pi supply hat also has that probably and no one has fixed it in a couple of years.
- 15155 2y agoYeah: don't use a Raspberry Pi or any similar Linux SOC to translate sensor data to TCP/IP. GP said "cheap MCU" - which I agree with. Ambiq MCUs use 1mA while active, but most ARM M0+ cores (RP2040, STM32) are going to be sub-50mA generally. Spin a $2 4L PCB with all the POE circuitry (and receptacle), MEMS microphone IC, and MCU onboard. This whole thing should cost <$25 total.
- hcfman 2y agoWell.. the project wasn’t intended to be an acoustic recording device for biologists. It was intended to be a microphone addition to a security project I have that would dynamically merge audio with video. Something you can’t do with microcontrollers. But along the way, I added a GPS to keep the time accurate and then with the sub-microsecond time accuracy I thought of sound localization. So I developed it further into a sound localizing recorder with in principle enough time accuracy to localize bats that are close even. With the power of a pi and sub-microsecond clock timing, coupled with a linkage into jackd that can support multiple consumers, you can both record and still have enough CPU to on principle perform real time bird recognition and localization. That is not going to be possible on a microcontroller. With this project I have been able to localize explosions to less than 20m accuracy from microphones located more than 3km away. Again not something possible on microcontrollers. The setup of the author is at his own home. Which means that in principle he’s not constrained by power. With that’s setup by adding icecast2 and darkice. Whilst still recording and not needing a big host host computer. Likely even better with go2rtc. Next on my list to try.
- 15155 2y agoWhy do you need to merge these items at the point of collection? Why not just stream the sensor data off with temporal correlation data and assemble them elsewhere? Either way, galvanically isolating 5W isn't too terribly hard either.
- hcfman 2y agoBecause you can. Why split the architecture across multiple machines when it works on one. Do you have any recommended links to that galvanic isolation I could look at ? I’m encouraged by your view on this.