Pace

- A Minute Timer for Swimmers

Description

I am developing a compact, magnet-attachable timer to assist swimmers with pacing during training and competitions, it's the size of a 1¢ coin (19mm).

Progress

After our pool closed, I stated making Pace - a goggle-mounted minute timer, the size of a dime, to help swimmers like me keep pace when training alone.

v1 Discrete components: 8 daisy-chained shifting registers, a 1Hz pulse oscillator, and a delayed latching circuit which provides the first input. My overcomplicated design got a slating review and I despaired at how expensive it would be to make.

v2 Programmable: STM32Lo microcontroller, controlling the LED array with a matrix driver. Due to space constraints, I switched from wireless charging to direct with a storage case. After a full redesign, ready to order, I realised that JLCPCB doesn't support buried vias. These vias alone would cost hundreds of euros. I was crushed.

v3 now consists of two stackable boards, a significantly cheaper, simpler solution. Pace is still a 6 layer PCB, but it will be significantly less dense.

Hopefully this will be the last major iteration of making Pace!




V2.0 - Using STM32Lo microcontroller & LED matrix driver

Swimming Timer Pacer V2 Current Schematic

V1.0 - Built with non-programmable discrete components

V1 Design V1 Schematic

My initial iteration used eight daisy-chained shift registers, driven by a quartz crystal oscillator. It also featured a latching circuit to create the initial 'bit' in the first register that would then cycle through and provide the cycling LED.

I ultimately decided to move away from this iteration due to its sheer complexity and production costs.

Initial pulse-generating latching circuit: This circuit provides the initial input 'bit' to the first shift register and latches to zero after the first clock pulse. The second video demonstrates daisy-chained shift registers.