Lamp test button pushing and all system failure ! S7-300

DEar all

I got a strange trouble in S7-300 system that when ever I push lamp test button, all system got failure (SF LED ON , communication with PG is OFF - disconnected). When I release the lamp test, the system came back to normal.

I try to force the input for lamp test button (NOT press the button physically), the error still happened. I suspect the Output module. Operators said that, this case did not happen before.

Anybody have any idea ?

Thanks and regards

Hi kietn81,

did you check the diagnostic buffer of you plc? If LED SF in on, there must be entries in the buffer.

Regards,

Towome

Hi Towome

The diagnostic indicate Power failure message. Actually, Power is OK.

kietnt81

Hi Towome

The diagnostic indicate Power failure message. Actually, Power is OK.

Oh dear,

that is an old well known problem.

You are using bulbs, not LED's.
The start-up consumption of bulbs is very high.
So, the voltage breaks down for a short moment by using lamp test, because all lamps starting at the same time.

Use a larger power supply or change lamp-test in this way, that not ALL bulbs light up at the same time. Use a short delay time between some lamp - groups.

Thanks IBN-Service

I will check and try to modify

Hi

It's fine now, the root cause is correct, bulbs caused problem.

Thanks much

You are welcome!