Industrial Automation Board, Optically-Isolated Input Connections


New member
In the general description for the board, it says that the optically-isolated digital inputs are "Read four optically isolated digital inputs, 0-24V", but in the user's manual it says "The Industrial Automation Card has four optically isolated inputs which can measure signals between 5V to 12V. Each channel has a 4.3K internal resistor in series with the input". I understand that the 5V is probably necessary in order to activate the LED, but what is the max that it can actually take 12V or 24V. Asking since the manual and website are inconsistent and I wouldn't want to over voltage that connection.


Staff member

If you use 24V to power the optocoupler you will have about 5.5mA current and about a 125mW on the series resistor. The optocoupler LED is rated to maximum 60mA continuous and the series resistor maximum power to 500mW. Except for the fact that these components will warm-up a little bit, you are OK with 24V. We will update in the manual, thanks for pointing this.