Hello everyone,
i have a problem with a SAFEX C.12. Two input of safety device are connected to a light curtain Shcmersal model SLG440-ER-0900-04-01 (https://products.schmersal.com/en_IO/slg440-er-0900-04-01-101216823.html) . As soon as light curtains are activated, they give an error on OSSD output:
He tried also with other light curtains of another brand and the problem is not present in this case. There are some restrictions in terms of OSSD signal at the input of SAFEX?
Thank you
Hello davifas,
The digital inputs of the SAFEX-C.1x generates 1.8V to 2.2V. If a digital output of an active safety device with OSSD signal is connected to the input of the SAFEX-C.1x, then the minimum voltage of the output is limited. The active safety device monitors its output that the signal can reach a minimum voltage. If it is not possible to reach the minimum voltage, an error is thrown by the active safety device. As you saw by using another brand of light curtain, different manufacturers\devices have different minimum voltage levels.
A work around\solution is to put a resistor between the digital input of the SAFEX-C.1x and GND. This will pull down the voltage. This solution does not affect the safety of the SAFEX-C.1x and is reliable:
In one example an active safety device required a minimum voltage of 1.3V. A 3.65 kΩ resistor (E48 EIA series) was used to reach the minimum voltage of 1.3V. As an alternative it is possible to use 3.6 kΩ (E24 EIA series).
The minimum voltage will need to be determined for the Schmersal light curtain then an appropriate resistor used to reach the minimal voltage level.
Select a resistor with the right power rating. E.g. 30V*30V/3600Ω= 0.25W. Check if the active safety device can deliver the additional current.