EDA > General PCB/EDA/CAD Discussions

solid state relay module

(1/2) > >>

Hello, I am trying to build a solid state relay module that uses the raspberry pi with shift registers to achieve a 25 channel relay module active high. I have been struggling to understand how these ICs work, and was hoping to get some clarification. I am using a Panasonic 4 pin SMD (part# AQY211EHAX), (LCSC parts library #C129282), SSR spst-NO, rated for 1A continuous current and up to 3A pulses. It is a photovoltaic (I think) power mosfet on the output. I feel confident about my understanding of the input side, I have an indicator LED with the appropriate sized resistor for both the LED and IR LED in the IC while using 3.3v. On the output side there are two pins, a source and a drain I would imagine. I have my load connected on the drain side. my load is a small piece of nichrome filament, used to light a fuse. the nichrome wire requires 1A between 12-18V. I've uploaded a picture of part of my design. on the left is the input, "OUT 201" comes from the shift register. on the left, 12v is connected to the source, and netport 201 goes to to positive lead of the nichrome and the negative of nichrome lead goes to ground to complete the circuit. Will this work in this configuration? 


I don't see why not, if the isolator can handle the current.

Here is a page which describes how the back-to-back configuration of the MOSFETs work to create a bi-directional switch:


The relay is bi-directional, so it so you don't have to worry about which end is connected to +12V.

And here is Panasonic's own "high-level" description of how their PhotoMOS devices work:


Thank you for the reply! After reading the articles, do I need a Schottky diode if I am only switching in one direction rather than bidirectionally? or am I way off here?

What Schottky diode are you talking about???

The circuit in your first post should work just fine assuming you get enough current through the LED.


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version