💡 SainSmart 4-Channel Relay Module: Versatile Control for Your Electrical Devices Review

This board *does not *work* reliably with Raspberry Pi. It is designed for 5V control inputs like those on the Arduino, while the Raspberry Pi 3, 3V used on its GPIO pins. There is a jumper on the board that can be removed to allow the input side of the optocouplers and 5V to be applied to the relay side, but I found that 3.3V was not enough to reliably trigger the relay. But there is a solution: just short-circuit the four LEDs. When they're on, they drop about 1.7V, which happens to be the…

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…

Works well, although the relays make a fairly loud noise when activated. For those interested in logic low and what happens when a device loses power, no power is not the same as logic low. When there is no current, the circuit is floating and the NO (normally open) side is effectively open (disabled). Going low closes NO and completes the circuit (the NC side is now also open, breaking that part of the circuit). You can easily control this from your Raspberry Pi with the Pigpio package, just…

This is a very well made relay module. Diodes are installed on the relay to protect the microcontroller from back EMF. There is a jumper on the VCC that can be used to create a kill switch. Each relay has a status LED. Each relay has three terminals: common, normally open, and normally closed. As others have noted, the instructions for use are poor at best, but to control a specific relay with a microcontroller one simply has to pull the relay pin low to turn it on and high to turn the relay…

So far this product has been flawless in making a germination chamber which I use Arduino and DHT-22 sensors to periodically check the temperature and humidity of the volume and then the heater turn on. and/or a humidifier with a relay. However, I would like the documentation to be more accessible. I was hesitant to run the module with just the Arduino because I'm not very familiar with the reliability of the electrical isolation and they are all capable of powering both the optically isolated…

Works great with Raspberry Pi! This thing is very responsive. It's worth every penny and then some. It was a pleasure working with him. And built-in LEDs (one per input/relay) help you test the inputs. How do you use this thing? Connect VCC to +5V. Connect GND to ground. Connect one of the IN1/IN2/IN3/IN4 to one of the GPIO/control pins. If the input LEDs don't light up, make sure you've connected VCC and GND properly. Use a multimeter to test this if you have one handy (and if you don't, buy…