Adafruit 555 PWM Output STEMMA - 1.5K~25 KHz or 1.5~250 Hz

The Adafruit 555 PWM Output STEMMA is a versatile, fully-assembled 555 timer board offering adjustable-frequency, 50% duty square-wave output. Developed initially as a PC Fan Dummy board, it transcends its original purpose to generate precise square waves for driving piezos, modulating IR signals, or serving as audio inputs.

With the capability to select between two frequency ranges—approximately 1.5K~25 KHz or 1.5~250 Hz—the included trimmer pot allows for easy tuning. Synchronize with devices using a logic analyzer, oscilloscope, or even through an audio input to find the exact frequency output.

The output is driven by a 74HC1G04 buffer capable of sinking/sourcing up to 12.5mA, and it maintains a DC square wave, pegged to 5V when powered over 5V. Power the board with a range of 3V to 12VDC; thanks to the onboard regulator, the 555 and buffer are safely regulated to a 5V maximum.

While each STEMMA board arrives as a fully assembled, tested PCB, users need to acquire a 2mm pitch, 3-pin STEMMA JST PH cable for connection. It also offers a 0.1" spaced header for those who prefer to solder power, ground, and signal paths.