sorry for a beginner question, but I can't find the issue. I bought two of these https://www.aliexpress.com/item/1005001281266972.html?spm=a2g0o.order_list.order_list_main.17.698e1802eEHtjq - a board with 2 relays and optocouplers. It has separate power supply 5V and 2 inputs (according to aliexpress page 0-2VDC means ON, 3-5VDC means off). I'm trying to control and power it with ESP32 dev board (ESP32 WROOM). However it doesn't work as I hoped:
Relay 1: works ok
Relay 2: I can hear a silent click when switching from ON to OFF, however the relay remains open.
Relay 3&4: I can close the relay, but when I apply the voltage to switch it off, the relay stays closed.
Power supply of the board is connected to 5V output of the ESP32, the inputs are connected directly to ESP32 GPIO pins. I know that ESP uses 3V3 logic, however according to datasheet, 3V3 should be enough to turn the relay off.
It seems I'm doing something wrong, but I dont know what. When I bypass the optocouplers (shorting with a screwdriver), the relay closes and opens as expected. Can you give me some advice please?