Teyleten Robot DC 1 Channel Optocoupler 3V/3.3V Relay High Level Driver Module Isolated Drive Control Board 3V/3.3V Relay Module for Arduino (Pack of 5)

These are great if you wish to switch using 3V3. So many others are 5V or higher. I wish the board was a bit smaller, but it seems about as small as it can be made.

Can be used from a ESP32 system which has 3.3V logic without any additional circuitry. Has screw terminal blocks for both sides of the relay making it easy to integrate with microcontroller board. Has a red LED that lights when the relay is activated, giving good operational feedback.Only niggle is that the screw holes are a bit small. i had to enlarge them with a file to fit normal sized standoff screws.

I’m using 2 of these to control a gas heater and a gas water heater with a Raspberry Pi 4. The 3.3v GPIO pins reliably open and close the relays. Homebridge and a bit of scripting and I can now use Siri and HomeKit to control decades-old home devices! It sounds like ESP and other lower-power devices sometimes have trouble driving enough amperage, but it seems like the Pi 4 works. The only downside is that you have to buy sets of 5, and there is only an LED to indicate whether the relay is open or closed (other similar modules have an additional power LED).

I'm using these to control the led grow light in a custom hydroponic set up I made. They allow me to remotely and programmatically switch on and off a grow light with my raspberry pi. I made a custom box for it all and an very pleased.

There are a lot of reviews for these clearly written by people using them in ways they are not intended to be used.I am using these to trigger different animatronics from an ESP32. I have 3 of them run in parallel with a 3v LED at the end of the chain. I am powering them from the ESP32's 3V3 pin. I am using a GPIO as the trigger. The ESP32, connected via usb to a computer, still provides enough amperage to trigger all 3 at the same time in addition to powering the LED.The relays support 250V@30A on the output side ONLY. Some people mentioning theirs caught on fire, but clearly are running voltage to the wrong rails.There's no documentation on the jumpers, but basically they are ground and VCC. I am not sure why they would be there, but I guess you could use them as headers to not use the screw terminals? this seems silly though as IN would still need to use the screw terminal.Overall these work great for my project.

These don't fit the wires you'd typically use in a Arduino project because they are too small but it's really easy to just desolder the connecter and solder your wires directly.

5/5 will not work with 3.3V, will however work with 5V. useless though considering the RPi outputs 3.3 from GPIO

Works perfectly with my ESP32 boards