I'm looking at the schematics for an electric vehicle "charging" station that uses a contactor to switch the main AC wires. Here's the interesting bit:
It uses 2 MID400 opto-couplers (
Datasheet) in different ways (as far as I can tell).
1. It uses one MID400 to sense AC line voltage.
This is exactly what it was designed for. Easy.
AC line voltage is connected to the Vin1/Vin2 side (the emitter) and the DC output signal is hooked up to the microcontroller. AC in, DC out.
2. It seems to use another MID400 in an inverted way to SWITCH the contactor on that ultimately powers the cars charger.
So, if I understand the schematic correctly, a microcontroller pin (5V) is hooked up to the input terminal (i.e. the emitter). The AC Line is hooked up to Vcc and Vo (in line). So DC in, AC out?!?!
Is this a common application for opto-couplers?
Why/how does this work?
Assuming the contactor coil probably draws a bunch of mA, is this safe?