I purchased 2 PLC Simple MAC modules. I made an arduino Program to send a string through one PLC and other the PLC receives that string and send to a computer using an UART/USB converter. I measured every voltage and recheck every connection. When I tried I worked but only 1 minute at 110VAC after that stop working and never work again. In both modules the voltages for VCC, TX and RX stay in 4.9V.