The output coming from this optocoupler will not activate the relay directly. This light will turn the phototransistor on and the optocoupler switches on. So when this circuit is powered the LED will receive the voltage and light up.

Here is the datasheet for the ILD205T, a. Optocoupler PC817 used here has an LED and a phototransistor in it. The opto-isolator can deal with differential voltages of up to 4000V. At the output side, it can drive loads up to 70V. a mechanical relay or an open-collector/open-drain drive circuit (optically. Pricing and Availability on millions of electronic components from Digi-Key Electronics. I am looking at this relay module: HiLetgo 12V 1 Channel Relay Module With OPTO Isolation Support High or Low Level Trigger, 4. 4N35 Optoisolator Transistor with Base Output 3550Vrms 1 Channel 6-DIP from Lite-On Inc. I want to provide some sort of isolation for the Arduino board, but don't want to have multiple power supplies, I want to use only the 12V power supply comes with the LED strip to power everything, so the picture is what I came up with after some research. Relays are also bulky when compared to most other parts of an electronic device. If I want to control the GR-55 switch externally via this second unit, I need to isolate the circuits so as not to fry the CPU in the GR-55 in case of some ground fault or other issue I might not know about. This is a 5V 8-Channel Relay interface board, Be able to control various appliances and other equipment with large. So I'm trying to control a 12V 5A LED strip with my Arduino, only the on/off, I want to make it turn on when somebody walks by. If used with isolated 3. Secund function of the relay and optocoupler interfaces is electrical isolation between sensors/actuators and the PLC.

First I want to say is I'm a beginner to Arduino and I know the same topic must have been asked many times, but after searching for a few hours I still have some questions unanswered. That 5V relay supply could be totally isolated from the 3.3V device, or have a common ground IF opto-isolation is not needed.

Opto isolated relay schematic