Olimex PICO-EVB Adds Mains Relays to Raspberry Pi Pico

A €14.95 Bridge Between a $4 Microcontroller and Mains Voltage

The Raspberry Pi Pico family is cheap, capable and completely unequipped to switch anything that runs on wall power. Olimex's answer, announced July 16 and covered a day later, is the PICO-EVB — an open-source-hardware carrier board that drops a Pico into a socket and hands it four relays and four optoisolated inputs rated for real-world voltages. At €14.95, roughly $17, it costs about three times the microcontroller it hosts and turns it into something you can wire into a control cabinet.

• Priced at €14.95 (~$17), with the Pico sold separately
• Accepts Raspberry Pi Pico, Pico 2, Pico W, Pico 2 W, or Olimex's RP2040-PICO30
• Four relays rated for 240VAC, plus four optoisolated inputs accepting 3.3–30V DC or 110–220V AC
• 100 × 70mm board rated from −45°C to +85°C, with USB-C, a UEXT connector and an unpopulated 18-pin GPIO header

What Makes This an Industrial Board Rather Than a Hobby Shield?

Three things, mostly. The first is the optoisolation on the inputs — accepting 110–220V AC directly means you can sense whether a mains-powered device is actually running without building an interface stage yourself. The second is the temperature rating: −45°C to +85°C is a specification you write down when the board might end up in an unheated outbuilding or a machine enclosure, not a desk.

The third is the UEXT connector, Olimex's long-running I2C/UART/SPI expansion standard, which opens the board to an existing catalogue of sensor and radio modules. There is also an unpopulated 18-pin GPIO header for anything the relay and input blocks do not cover, and a USB-C port for power and programming.

Software That Meets Makers Where They Already Are

Olimex published KiCad design files along with Arduino and MicroPython samples — including a MicroPython web server that serves a browser UI for the relays — and, notably, ESPHome and Home Assistant YAML. That last inclusion matters more than the sample code, because it means the board arrives already speaking the language of the most common self-hosted automation stack rather than asking you to write an integration first.

It is a good complement to the ESP32-based work we have covered recently, like the wM-Bus gateway that feeds utility meter data into Home Assistant. Where that project is about reading, PICO-EVB is about acting.

How Does It Fit the Rest of the Pico Ecosystem?

The Pico line has been quietly accumulating exactly this kind of infrastructure — see also the driverless USB WiFi adapter work from earlier this week. The pattern is a microcontroller platform maturing past the demo stage into one where the surrounding boards, drivers and integrations are boring in the best sense.

One note for anyone ordering: coverage of the relay specification has been inconsistent across write-ups, with the current-handling figure reported differently in different places. The 240VAC rating is consistent everywhere, but check Olimex's own repository for the amperage before you design around it. Design files and examples are on GitHub, which is the right place to confirm. More compact-computing coverage lives in our mini computers section.

Sources: CNX Software — July 17, 2026; Olimex blog — July 16, 2026; OLIMEX/PICO-EVB on GitHub.