Note from the author: Assembly service for this project is strictly forbidden here.

Griff the superstar Noctule is a 384kHz ultrasonic mic for bat detection / recording. I'm grieving right now, Griff passed away on the 17th July 2025. He was a very special bat, he changed lives and touched hearts, and I would like to keep his memory alive by keeping his name on these designs.

NOTE : Gerbers changed on 4th October 2025. No components moved, so stencils from the previous version are good, but the PCB has grown by about 1.5mm in both directions so you will need to build a new frame.

IMPORTANT : MAKE SURE YOU ORDER A "NO FRAME" STENCIL. The framed version is HUGE and shipping is expensive.

This revised, simplified and cost-reduced version of Griff features holes in the corners and bottom centre to allow him to be permanently stitched or cable tied to a hat or jacket, but he can also be attached using a brooch pin. There are solder points on the PCB to allow a 38mm brooch pin to be attached during the hotplate pass, alternatively a brooch pin can be hot-glued after assembly, or omitted entirely.

Layout and component placement has been rationalized for the simplest possible assembly, and most logical grouping of components. There are just 5 resistors and 5 capacitors in total, plus the op-amp and microphone. Looking at the component side, the 7 components associated with power rail conditioning and bias voltage delivery to the op-amp and microphone are on the left of the microphone. The remaining three components tasked with managing the audio signal signal - the AC coupling capacitor, the input resistor and the feedback resistor - are on the right. Measured - and filmed so you can take notes - at 4 minute paste application / component placement, with a subsequent 4 minutes on the hot plate to deliver a working 384kHz USB microphone : video here https://www.youtube.com/watch?v=qv38JZPgvKo

Shopping list for electronic components : https://www.digikey.co.uk/en/mylists/list/HEJJQAEWTN

NOTE - for maximum economy, remove the Raspberry Pi Picos from the shopping list and instead grab 10 Pico clones from AliExpress. They work perfectly and will save you about £2 per Griff. e.g here : https://www.aliexpress.com/item/1005007525241877.html - you will need 10 "original micro" or "USB-C", NOT Pico 2, NOT Pico W. UK delivery time is about the same as PCBWay / DigiKey so you will not get held up.

The brooch pins are specifically 38mm long. without the "locking back" - I got them on Amazon, about £4.29 for 50 : https://www.amazon.co.uk/Pcs-Silver-Bar-Pins-Safety/dp/B0CQH72K3V?th=1 - if the link goes dead, just search for 38mm brooch pin.

NOTE TO PCBWAY - this is NOT a panelized design. The extra part of the PCB that has no electronics on it is to allow purchasers to build a frame for solder paste stencilling. PLEASE do not charge buyers more than $5. PCB assembly is NOT authorized for my projects. PCBWay - you must NOT assemble PCBs when requested. Buyers - please do not attempt to order PCBs with assembly, they will be declined.

UNDER NO CIRCUMSTANCES MAY ANY DEVICES BUILT BE EITHER RESOLD, OR OFFERED FOR SALE. THIS PROJECT IS SUPPLIED ON A STRICTLY NON-COMMERCIAL BASIS. I MAKE NO MONEY FROM THIS PROJECT, AND IN RETURN, BY BUYING PCBS HERE, YOU COMMIT TO MAKE NO MONEY FROM THIS PROJECT. BE NICE, OK?

Griff's very own Instagram : https://www.instagram.com/griffthebat/