Micrologix 1100 For Hands-On Projects

Belated Merry Christmas and Happy New Year to all. I wish everyone well for the new year.

I bought a Micrologix 1100 processor (1763L16BBB) to use for some hands-on projects at home and 4 of the 6 DC outputs are Field Effect Transistors (FETs). I have read a few posts to the fact that when FET outputs are used to control lamps for example, they tend to not switch on and off as intended. Does anyone know of any problems with FET outputs? On the other hand, what advantages do FET outputs offer over Relay Outputs apart from the fact they do not have any moving parts and tend to last longer? This is not going to be used for industrial application. Thanks for any information anyone is able to provide and thanks for everything all of you continue to do on this forum.

Sometimes you need to make sure you have a load on them or a large enough load to make them switch if your load is to small then just use a small resistor with the load and you will be fine, I have not found any issues with "control lamps" (like with my trainers) but in the early days I did notice some with LED's as I think they did not have enough draw on them

They are faster then relays and will not go bad if you are cycling a lot... but when they do fail then tend to fail closed, I would prefer failing open.

They can short out easy if not wired correctly or just shorted for a nano sec I hate when that happens

So check the current draw on the load if to much then use a interposing relay as they cannot handle much of a load then you should be fine, they are great little CPU's

I appreciate your explanations. I think I will be better off with a processor that has isolated relay outputs rather. This is the first trainer I'm building and I will hate to damage over $300 processor because I fail to add a resistor with the correct rating to a load. Thanks for input.

if you already have the PLC, i would just wire the outputs directly to relay coils for a trainer. Then you don't have to worry about shorting out PLC outputs, output voltage, or relays getting welded. If you mess up a relay, it is quickly and cheaply changed out.