I bought this 5V Relay Module 4 Channels for Arduino, but it turned out to be disappointing. The first and second relays had a serious problem: they were leaking current from the NO (Normally Open) contacts, even when there was no activation! This makes its use dangerous and unreliable for applications where absolute control over the opening/closing of the circuit is required.

Additionally, the build quality seems low. The soldered components do not look sturdy, and the PCB looks cheap. For testing applications, it may be acceptable, but for serious projects that require safety and stability, I would not recommend it.

If you are looking for a reliable relay module, it is better to invest in something of better quality. Disappointing experience!