A tiny driver board with 8 solid-state relays and a multiplexer for high-power switching applications
The Tiny8SSR board is an ultra-low profile relay board with 8 solid state relays (TLP241A). The board dimensions are only 1.71in x 1.66in (43.5mm x 42mm). Tiny8SSR provides two input methods for controlling the 8 relays - a standard control input and a dual-mux control input. With the standard control, 8 inputs pins are used for controlling the 8 relays individually. With the Dual-Mux control, only 4 input pins are used for controlling the 8 relays via a dual 1:4 Multiplexer (74CBTLV3253). This control approach not only saves I/O pins, but also allows for effortless time-multiplexing, and furthermore it even allows controlling up to 2 relays synchronously! The inputs and outputs of the board are designed to be suitable for connecting them to both jumper cables and ribbon cables. The board was engineered to be compatible with both 3.3V and 5V logic and power signals. Since it's using solid state relays (SSRs), there is no clicking noise during switching operations, as would be the case with electromechanical relays. Each SSR is rated up to 2A load current, has a fast switching speed of less than 5ms, and ON-state resistance of 0.1ohm.
The "Enable" inputs of the multiplexer are Active LOW, so we have them connected to pull-up resistors to ensure that if no signal is applied to the multiplexer control header, the mux will remain disabled.