Hi,
I am currently working on a design to control lights base on existing alarm switch and motion sensors. My 25 years hold home automation has died and I will replace it with Home Assistant (HA).
About 5 years earlier, an alarm company already installed a new alarm panel and tap on the siren to send alarm on the central. So the central alarm will always tell me that the alarm is in the same zone.
I want to replace my hold home automation died panel on the first floor by the newest one.
The alarm technician will take all the wires from the existing switches and sensors and connect them to the newest panel. At the same time, I will ask him to also connect them to my HA. Because the wires will be connected into another board that I don’t really know the exact voltage use, or there might be a pull up resistor to 14 VDC. I want to isolate the HA system, I mean the Raspberry GPIO pins with optoisolators.
I did some experimentation and do not have a real success and I want to ask the community for advice. My main problem is caused by the internal pull up resistor to 3.3V I think. If I connect the switch directly to the GPIO pin, it works fine, adding my optoisolator circuit, the voltage to the GPIO pin do not drop enough to trigger the switch. If I test the optoisolator alone, not connected to the GPIO pin, the voltage drops very low.
I tried to add a CMOS gate and again, with the GPIO pin not connected, the voltage on the output pin drop to 0 V, but with the GPIO pin connected, the voltage drop only to about 1.7 V. It looks like the CMOS gate does not drain current enough to bring it to 0 V.
Any advice?