Sagar Saini's Compact PCB Packs Four Solid-State Relays for Silent Power Switching

Maker Sagar Saini has designed a compact four-channel solid-state relay module, designed to deliver power switching without the usual "click" sound and without taking up too big a footprint.

"I want[ed] to make a relay module which can fit into a small housing space," Saini explains of the project, "and I don’t want that clicking noise any more of standard relays. Today in this project we have [the Omron] G[3]MB, which is a solid state relay module, widely adapted for its performance. Low cost 'SIP' package switches up to 2A loads, built in Snubber circuit, and input resistor as option."

The main draw for Omron's G3MB relays: they're considerably slimmer than standard "clicky" relays, with no moving parts and silent switchover. As a result, Saini was able to design a printed circuit board that puts four of the relays into roughly the footprint of two traditional relays — though the overall footprint is increased through the inclusion of a bulky-by-contrast 220V to 5V power supply module.

"The circuit diagram is quite simple," Saini explains. "We have a power conversion unit onboard which helps in switching of these relays. And to make them controllable through a single pin we have transistor drivers, the base is pulled low with the help of 10k resistors. The circuit does not have any capacitor but you can add one between the 5v and GND power line."

Saini's design is documented in full, complete with schematics and Gerbers, on Hackster — but it does involve unfused mains-level voltage, and thus should be handled with considerable care if built.