I have designed a compact enclosure for an AZDelivery (Wemos) ESP32 D1 Mini NodeMCU WiFi microcontroller, including space for an optocoupler module and cable clamp for an RS485 Modbus or S/FTP cable.

I use this setup to create a dry-contact to provide an SG-ready heat pump, via ESPHome and HomeAssistant, with a (simulated) S0 pulse signal. See my GitHub repo [link] for more information.

The recesses for the ESP32 and optocoupler module are designed with 0,2...0,4 mm clearance, which should be sufficient. If the ESP32 module does not fit, check the opening for the USB-port (sometimes it sags).

Check whether you need to adjust the holes for the threaded inserts to be able to melt them in properly.
I used the nominal dimensions for the model, but had to increase them by 0,1 mm for my own print due to dimensional inaccuracies when printing small details.

List of materials I used to complete this print:

• SUNLU PLA Matte (any non-conductive filament is suitable)

• Ruthex RX-M2x4 threaded bushing    (Amazon.nl)

• ISO 7380 - M2 x 8   (KINGMicroschroeven)

• AZDelivery (Wemos) ESP32 D1 Mini NodeMCU WiFi microcontroller   (Amazon.nl)

• 0,34 mm² (22AWG) wire

• EGBO 3...5V one channel optocoupler isolation module PC817   (nl.aliexpress.com)

Connect GPIO25 of the ESP32 to the positive (+) terminal on the input side of the optocoupler module.
Connect GND of the ESP 32 to the negative (-) terminal on the input side of the optocoupler module.

If you are not using solid wires, use wire end ferrules or solder the ends of the wires.
This prevents poor contact (transition resistance) in the cage clamp of the optocoupler module.