WiFive55 Is an Enhanced ESP-01 Wi-Fi Relay Module and More

TechColab needed a way to control a solenoid valve using a short pulse with an SSR (solid-State Relay). Typically, he could have used a 555 timer and be done with it, but he found that the timer worked ok, but wasn’t very convenient. He also wanted to set different pulse lengths and switch between them instantly without issue. Moreover, he wanted the ability to maintain a pulse on a maximum, even if he left his finger on the button.

To that end, the 555 wouldn’t do, so TechColab designed the WiFive55 – a replacement board based on the ESP-01 ESP8266 module. He first tried implementing existing ESP-01 SSR boards but found a majority of them briefly enabled the output upon startup, which was ultimately solved with the WiFive55 be adding an RC filter to the SSR output. Adding the filter to the output came at a cost, however, as it slowed switching time by 20-milliseconds, but it was a tradeoff TechColab could live with.

Considering he was developing a new PCB, TechColab decided to implement additional features, including an optoisolator that can switch up to 1 A, a MOSFET for switching up to 2 A, and an additional onboard relay for switching up to 3 A. There’s also a header for an off-board SSR, which allows it to handle whatever current the connected SSR can accept. Rounding out the WiFive55 features are the ability to control the unit via Wi-Fi, GPIO, Serial, and a push-button. Finally, TechColab included equipped the board with a 555-like trigger and output interface.