I2c optical isolator serial#

This clever H-bridge uses the optos as logic elements as well as isolation.Ī final example of a good use for optocouplers is connecting logic circuits up to beefy motors with an H-bridge circuit. Any input to the microcontroller or output from the microcontroller will need to pass through the LED side of an opto to keep you from getting shocked. For instance, a project that uses a transformerless power supply should be isolated because what the microcontroller sees as “ground” may be up to a few hundred volts off from earth ground.

Just as important, an optocoupler can protect the rest of the world from your microcontroller if it’s running at an odd voltage.

I2c optical isolator serial#

There’s no common ground to hum at 50 Hz (here), but the serial data gets through: current signal → LED → (created light) → phototransistor → current signal → isolated device. It signals the synth by sending up to 5 mA down the cable, lighting up the LED inside the opto, and pulling down the “To UART” line on the left side. Imagine that my microcontroller is on the right side of this circuit, plugged into the synthesizer’s MIDI-in port. How can they do this without a common ground? All devices with a MIDI-in port send the voltage over the wires straight into an optocoupler. But my little microcontroller needs to speak 31,250 baud serial to the other microcontrollers in the synthesizers. I was just building a MIDI-compatible device, and because MIDI connects musical instruments together over a distance, there’s the possibility for a ground loop that could make an audible hum in everything that’s plugged together. The only connection between the LED side and the transistor side is non-electrical - light across a small gap - and that provides the rock-solid, one-way isolation. So while implementation details vary, the crux is that your microcontroller turns on an LED, and it’s the light from that LED that activates the other side of the circuit. But there are many choices for the receiver side: photodiodes, BJT phototransistors, MOSFETs, photo-triacs, photo-Darlingtons, and more. What is an optocoupler anyway? The prototype is an LED and a light-sensitive transistor stuck together in a lightproof case. And while simple on-off control of a device through an optocoupler can be as simple as hooking up an LED, they are not perfect digital devices.īut first a step back. When it comes to isolating your microcontroller’s sensitive little pins from high voltages, ground loops, or general noise, nothing beats an optocoupler.

Much like the brain inside your own bone-plated noggin, your microcontroller needs protection from the outside world from time to time. Deep in the heart of your latest project lies a little silicon brain.