The Relay Board gives your board the ability to control high voltage/high current devices, and easily makes normal home appliances become intelligent. Can be accessed programmatically or directly by shell. Up to 4 layers can be stacked.Switch the I2C address of the device through the DIP switch on the circuit board to ensure that the four-layer module gets different addresses, thus avoiding the problem of address duplication.The 4 Channel Relay uses high-quality relay modules combined with the most popular microcontroller technology to communicate with the for Raspberry Pi. You can use mulitiple relay modules stacked together to add many channels; You can stack up to four layers.The 4 Channel module is very fast, easy to install, and supports multi-language development, making it perfect for smart home projectsSwitch the I2C address of the device through the DIP switch on the circuit board to ensure that the four-layer module gets different addresses, thus avoiding the problem of address duplication.4 Channel Relay Hat Board For Raspberry Pi is one of the "pi" module.It has a 4-channel relay, it is the best choice for smart home projects.This four-channel relay uses high-quality relay modules combined with the most popular microcontroller technology to communicate with the Raspberry Pi.You can use multiple modules stacked together for use.You can stack up to four layers.Switch the I2C address of the device through the DIP switch on the circuit board to ensure that the four-layer module gets different addresses, thus avoiding the problem of address duplication.The module is very fast, easy to install, and supports multi-language development, making it perfect for smart home projects.Product FeaturesEasy to install, ProgrammableControl directly(without programming)Extend the GPIO Pins4 channel relay4 Alt I2C Addr SupportCan Stack with other Stack boardSupport multi-language programmingSupport 3A 250V ACSupport 3A 30V DCSupport address switching by dial switchSupport relay status light promptIndependent of the mainboard hardware (require I2C support)Compatible with 24AWG-30AWG wireProduct Advantage:Independent of the programming language, it only need I2C protocol supportYou could use the command control directily instead of programmingUse the raspberry pi to replace the trandition switchCompatiable with multiple protection boardsize:13x8x4cmMaterial:ABScolour:As shownPackage Contents:1 x Channel Relay Hat Board4 x M2.5x11+6 copper stick4 x M2.5x5 screws & nutsOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.