@kine90 said in ATOM HUB AC/DC, RS-485 VOLTAGE CONVERTER, VOLTAGE PROBLEM: I am working on a project where the switch is controlled by the M5 PIR SENSOR. When I power the ATOM from USB everything works fine, when I power it with a 12V 3A PSU thought the RS485 voltage converter the PIR begins malfunctioning (fake triggers). I checked the voltage of the two groove outputs (from the hub and from the atom lite) under USB and 12V power. As long as USB is connected, the interfaces shows a quite stable 4.98V. When the USB is unplugged, leaving only the 12V power source, the voltage drops to 3.3-3.28V, if the atom is removed it goes back to 5V I guess this is causing the PIR to misbehave, since it requires 5V. What´s wrong? According to labels on the components and to the HUB schematics, I expect 5V 2A from the DC/DC converter. [image: 1617022245614-1-resized.jpg] [image: 1617022237243-2-resized.jpg] [image: 1617022251558-3-resized.jpg] [image: 1617022264667-4-resized.jpg] [image: 1617022252907-img_20210329_144131-resized.jpg] [image: 1617022277105-switch_schem-resized.jpg] Based on your photo's you haven't connected the 12V to the correct pins of the RS485 connection. 12V needs to be connected to the RS485's red and black pins.