This trinket initially began as a party gift for my son's first birthday that was 65mm in diameter. It went through several iterations to get it down to a 25mm diameter. A simple electret microphone feeds an op-amp to amplify the input and drive a set of color LEDs visible on the front. The front contains an image of a crying baby in silkscreen and solder mask reveal. All the components fit on the back, and it also contains a battery and usb charger.
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