Yesterday the last parts for the OpenTherm Monitor arrived, so I could finish that part last evening:
– Adding the last part to the PCB (a 4.7 Ω resistor);
– Removing a diode that was there to power the PCB from the RS232 port that I won’t use;
– Replace the 2nd “RS232 power” diode with a wire;
– Cut away the unused headers.
And this is the end result:
Next step was to have a close look at the additional parts that are needed to connect it all to a JeeNode:
On this part of the schematic (here’s the complete original), 5 new parts are being used:
- 2 resistors of 1 kΩ;
- 2 * 2N7000 MOSFET (available here)
pin 1 = Source
pin 2 = Gate
pin 3 = Drain
is enough to make no mistake with the wiring, even if you have no clue what the 2N7000 does 😉
As can be seen in the schematic, a Single 2 input positive OR Gate would suffice just as well; maybe they exist too, but I didn’t bother to search
Yep, I’m waiting for the MOSFETs to arrive. As soon as they arrive and I have some time to finish the breadboard, I’m going to put this OT Monitor between the Honeywell Evotouch Wireless OpenTherm RF module and our Remeha Calenta.
Assuming everything keeps working and that I’m not confronted with errors on the display of the boiler, I can try to have a look at the signal on the data pin – and if that looks OK, the next step will be connecting the data pin to the JeeNode and watch the LCD… exciting!