1769-L16ER-BB1B Embedded Digital Output Endurance

zacslade

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Oct 2014
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Phoenix, AZ
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Hi All,

I have an application where I am supposed to make this light flash under certain conditions, using an embedded digital output on an Allen Bradley 1769-L16ER-BB1B.

I want to know how many times these internal, embedded relays can toggle in their lifetime before they fail. If it's more than, say, 30 million, then I suppose I don't have anything to worry about. If it's less than, maybe, 5 or 6 million, then that's a problem for me.

If operating conditions matter, they are not in a location with any significant shock/vibe. The temperature and humidity are controlled in a dry, human-comfortable range.

Can anyone point me to where this information is recorded? I haven't been able to find it in the manual. (Maybe I just keep missing it?)

Thanks in advance!
 
When operated within their specified current limit, the solid-state outputs on a PLC controller (like this one) have an very long lifetime because they don't have the physical wear of an electromechanical relay.

Power transistors and solid-state relays do heat up and cool down as they cycle, so it's very important that they be run within their rated current capacity.

You'll find estimates that a typical solid state output can cycle on and off for between 2 million and 50 million hours.

A PLC output that's just running an LED indicator lamp can be expected to run indefinitely. The LED itself should be good for about 50,000 hours of on-time.
 
The outputs on that model PLC are transistors so the number of cycles are almost limitless. The easiest way to destroy a transistor is by having it switch a load that is too high. So you may want to put a interposing relay in the circuit. A lot will depend on the light you want to switch and it’s current draw.
 
I once used real relay outputs for something similar, they lasted about 3 months. The operator panel had 50+ push-pull maintained illuminated red buttons for control; Center maintained was 'Auto", Push momentary was E-Stop, pull was maintained "Manual Override". Lights were only supposed to be flashing when an operator put a part of the system in manual override, letting him know that it was operating that way because there were potentially serious sequencing consequences. I got called out 3 months later, the operator had all of them pulled out and was wearing sunglasses to avoid getting a headache. He believed he could manually control it better than my program was controlling it, albeit ignoring all of the safety interlocks I had. The relay contacts had welded on about 1/2 of the outputs.


The outputs built into the CLX processor however are all solid state, shouldn't be a problem.
 

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