Relay
A relay is an electrically controlled switch that uses a coil and moving contacts to open or close another circuit.
Part images
What it is
A relay is an electrically controlled switch that uses a coil and moving contacts to open or close another circuit.
How students use it
Students use relays to switch a separate low-voltage load while the Pico controls only the relay-driver side.
Pins and power
Coil pins plus contact pins for normally open, normally closed, and common. Confirm against the relay package/datasheet before wiring.
The relay image shows a Songle SRS-05VDC-SL marking with 5V coil family and printed contact ratings of 3A 250VAC / 30VDC. ObsoleteHQ beginner projects keep relay loads low-voltage DC only.
SunFounder explains normally open contacts connect when activated, normally closed contacts connect when inactive, and the coil moves the armature.
Voltage and safety
A relay coil is not a GPIO load. Use a driver circuit and flyback protection as required. Do not use mains-voltage loads in beginner ObsoleteHQ projects.
Keep relay projects low-voltage DC. Never switch wall power in student projects. Power off before moving contact wiring.
Module internals
Main component: Songle SRS-05VDC-SL relay marking visible in the SunFounder source image.
Electromagnet coil, iron core, armature, spring, normally open contact, normally closed contact, common contact, and molded frame.
Datasheet notes
The SunFounder image visibly marks Songle SRS-05VDC-SL. Use the SRS-series datasheet and the exact package marking to confirm coil/contact pinout and ratings.
Common libraries
No special library is needed. Use machine.Pin to control the relay-driver circuit.
Common mistakes
Confusing NO and NC, driving the coil directly from GPIO, forgetting flyback protection, using contact ratings as permission to switch mains, and not sharing ground on the control side.