Review on 💡 SainSmart 4-Channel Relay Module: Versatile Control for Your Electrical Devices by Carlos Abood

What a great Arduino output interface; and only ten dollars! Works great, great quality. When you receive it you will find that each of the 4 outputs has NO/NC contacts. That's good, you can choose the one you need. but the relays are activated by a digital LOW input. This may conflict with your plans as the Arduino output will initialize LOW and this may cause problems with the relay switching at power up before the program initializes. However, it is easy to fix. Arduino outputs can be initialized HIGH before they are ready to draw current. Study the following Arduino setup code and you'll save time looking up this information elsewhere: void setup(){ pinMode(RelayK1ctrlPin,INPUT_PULLUP); //set up relay control pins Hi before switching to output PinMode(RelayK2ctrlPin, INPUT_PULLUP); // PinMode(RelayK3ctrlPin, INPUT_PULLUP); // PinMode(RelayK4ctrlPin, INPUT_PULLUP); // PinMode(RelayK1ctrlPin, OUTPUT); // Reconfigure relay control pins as previously initialized outputs Hello PinMode(RelayK2ctrlPin, OUTPUT); // PinMode(RelayK3ctrlPin, OUTPUT); // PinMode(RelayK4ctrlPin, OUTPUT); //