I am working on a circuit where I am using multiple ultrasonic sensors which work on 24V, to read the sensor output through a microcontroller that accepts 5V. I am using optocoupler PC817 to maintain isolation between them and the Microcontroller so there is an isolation circuit for every sensor these circuits take up lots of board area when schematic of isolation circuit I place them like an array-typearray of optocoupler isolation circuit pattern and I want to minimize the board area. my question is can I place one optocoupler SMD version just below the other to minimize the board area? one isolation circuit on the top layer and another just below it on the bottom layer

PC817 datasheet

  • \$\begingroup\$ No need to use a 1A schottky when something like a BAT54 would be adequate. Why a 100nF cap across the opto? Use software to filter the signal. \$\endgroup\$
    – Kartman
    Jun 29, 2022 at 12:08

1 Answer 1


Yes, you could do that. It would be better if they are directly on top of each other so there is no capacitive coupling through the PCB from input to output of the optos.

I would also suggest looking at SMT quad optos which are much higher density. You could also eliminate one of the 2.4K resistors per channel by connecting the LED in series with the optoisolator LED.

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