This post is part of a series on designing a wireless microphone system for hybrid online meetings, i.e. with some people present in person and others present online. See also the previous and next post in this series.
I want to design a wireless clip-on “Lapel” microphone based on the LOLIN32 lite board and the INMP441 I2S microphone module (not to be confused with the INMP 411, which has analog output). Given the size of the board (about 25 by 50 mm), an 802040 or possibly an 802540 Lithium Polymer battery would be a nice match. These LiPo cells are 8 mm thick, 20 (or 25) mm wide, and 40 mm long. In a few iterations, I designed a simple enclosure in Fusion360 and 3D printed them.
The box has a port in the top for the microphone; on the inside are two rails to keep the ESP32 board in place. The microphone is mounted in a small holder that clips perpendicular onto the antenna-side of the ESP32 board. The micro-USB connector is exposed at the bottom, this allows charging the LiPo battery. I expect that this design will also allow making a docking station for charging multiple microphones at once, for example, using these male micro-USB connectors. The first versions (red and blue) did not have an on-off switch; I added these in the later versions of the design (green, yellow).
The ESP32 wifi microphone enclosure is about 57x28x18 mm in size. For mounting the microphone on a lapel or in the neck of a shirt, I considered 3D printing a clip. However, I know from experience that 3D printing a clip with exactly the right flexibility is not so simple, since that depends on the properties of the filament. The clip would also make the 3D printing and assembly more complex. I think that a magnetic name badge holder will be a good alternative to a clip for mounting the microphone to your clothing; it has the advantage that the microphone can be positioned more flexible, especially for informal clothing such as t-shirts. Using double-sided adhesive tape the magnetic name badge holder can be attached to the recesses at the back of the 3D printed microphone enclosure.