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Transistor Output Help

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Hi guys


I am looking for a bit of help regarding the Transistor Outputs of my E3XB snap in module.


I have made a mistake when planning my current project and have left myself 1 relay output short.  I am controlling a simple on / off 24 vdc solenoid valves with all the outputs of the E3XB.  


Is it possible to control a solenoid valve with the transistor output in the same way as a normal on / off relay output?  If so, how can I go about it?


Any input would be appreciated!





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You can use the transistor outputs the same way as you would a relay output. Currently outputs 2-16 in the hardware configuration of the E3XB correspond to the 15 available relay outputs. In the hardware configuration you can use the two transistor outputs, Output 0 and 1 respectively, as a regular output and reference them directly in the logic. Doing this will not allow you to use the outputs as high speed, but it will then work in exactly the same way as the relay outputs.

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Just check the current rating - the relays (O2-O16) are 3A but transistors (O0 and O1) are only 0.5A (from the datasheet).


Also make sure you have a flywheel/freewheel diode on the solenoid coil.  (see the section "Increasing Contact Life Span" in the datasheet)


if the solenoid requires more than 0.5A you will need to add an interface relay between the PLC transistor output and the solenoid.  I would suggest doing this anyway if possible, to give yourself some insurance.

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