Official USB microphone for "Bat Detector" App

PLEASE READ THIS

THIS PROJECT IS PROVIDED BY THE DESIGNER AS A SELF-BUILD PROJECT FOR HOBBYISTS AND BAT ENTHUSIASTS. I MAKE NO MONEY FROM THIS PROJECT.

THIS IS NOT AN OPPORTUNITY FOR YOU TO BUILD AND SELL, OR TO ORDER AND SELL. PLEASE DO NOT TAKE ADVANTAGE OF MY GENEROSITY.

PCBWAY IS NOT AUTHORISED TO ASSEMBLE THESE FOR YOU, AS THERE IS AN EXISTING COMMERCIAL MANUFACTURING PARTNERSHIP IN PLACE. I MAKE NO MONEY FROM COMMERCIAL SALES, MY ROYALTY PAYMENTS GO TO CHARITY.

ANY ASSEMBLY ORDERS WILL BE CANCELLED.

Notes on this revision

Monday 5th August : now tested, works great. A revision has added a ferrite bead into the LDO circuit, plus an additional 220ohm resistor, all changes to the power supply circuit to try to tame some of the energy bands coming from the USB interface. Additionally the PCB outline has changed to include extra "snap-off" sections of blank PCB to build a solder stencil frame without having to order extra PCBs, and also to operate as a paste squeegee.

Thursday 18th July : version 2 changes the gain of the op-amp stage, dropping from about 46dB to about 38dB. You will see much less overloading / clipping in the amplifier now. Additionally an LDO has been added at the cost of about 29p per microphone to more strongly decouple the analog stage from Pico and USB-related noise. This removes a couple of strong energy bands in the 120-130kHz region.

What it is, what it does

A class-compliant 384kHz USB microphone for use with the iPhone / iPad app Bat Detector.

Just flash your Pico, build up the PCB, connect it to your iPad or iPhone and run Bat Detector.

Download Bat Detector here : https://apps.apple.com/gb/app/bat-detector/id6504186190

Firmware download for Raspberry Pi Pico : https://drive.google.com/file/d/1cd7lpe7WtJcLpagGEi3KyR9xy6Qd6IDG/view?usp=share_link

DigiKey shopping list : https://www.digikey.co.uk/en/mylists/list/JKMOPCPWZI - you will need to specify 2 assemblies to buy enough parts to build 10.

3D printed holder

This project also contains a 3D print model for the clip-on mount shown in the video. Note that the 3D print design makes 5 mounts. If you order 5 PCBs, only order 1 3D print. If you order 10 PCBs, order 2 3D prints.

Project cost

Total cost for a build of 10 is around £114 for PCBs, stencil, shipping, 3D prints and DigiKey components, so each USB microphone costs just over £11 including 3D print.

Video of build - 7 minutes total, assembly time under 3 minutes, the remainder is melting time on the hotplate. I estimate 5 devices in well under 30 minutes. I have also build these using unleaded solder on an Amazon £7.99 hotplate with great results. The trick with the cheap hotplates is to recognise that they heat up too quickly for the heating profile of the solder paste, so until the solder starts to fume, pulse the hotplate - turn it on for 5 seconds, off for 10. The cheap hotplates can melt 2 USB microphones at the same time.

Questions?

If you have question don’t ask them here, I have no idea how to respond to questions asked on this site.

Just email me on pipistrelledetector at gmail dot com and I will get back to you