NC and 8k2 safety inputs in control units for automatic gates.

When we think of an automation system, we cannot but think of its safety devices and thus: sensitive edges, photocells, mass detectors, etc. The connection of control units to these devices in recent years has evolved just like the protection devices.

The input perhaps least considered is that of the 8k2 ribs.

But what does this 8k2 input do and for what purpose?

Let us start from the assumption that the safety of an automatism is also, and above all, the safety that the system functions correctly. Therefore, electronics also evolve to check that the connection circuits and safety devices are fully functional at the moment the automation starts to move.

From this perspective, an NC input is difficult for the control unit to monitor, as any short circuit on the spinning is undetectable.

So what does an 8k2 input actually do?

This input 'expects' to read a resistance of 8200 ohms. So it goes without saying that you can only connect devices that are born with a series resistor of 8200 ohms or you have to put it in series.

In this case, if the connection line between the safety edge and the control unit shorted out, the control board would immediately realise the fault and take action.