#04-8, M1S: Four 24V Isolated Inputs, Common Ground


Function: Four opto-couple inputs with the '-' terminal connected to the system ground, independent '+' terminals

Form factor: M1S

Category: Input module

Special needs: ---

Power requirements: 5V/40mA

Mates with: #19, #20, #21 (limited use)

See also: #04-1, #04-2, #04-3, #04-4, #04-05, #04-06, #04-07, #54



This Tibbit is optimized for the nominal input voltage of 24V. If no external resistor is added these inputs activate at about 13V. Forward current should not exceed 10mA, and this caps the maximum input voltage at around 30V. Add external resistors if you need to apply higher input voltage.

Note that these are not "isolated inputs" — they share the ground line with the rest of your system. Still, the optical stage isolates your system from noise, ESD, spikes, and other external influences.

Combine this Tibbit with terminal block devices — #20 (nine terminal blocks) or #21 (four terminal blocks).


There are four green LEDs which are connected to four control lines. LEDs light up for the LOW state of control lines (i.e. when current passes through the diodes of the opto-couples).