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FX1S output failure

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Hi guys

I have an Mitsubishi FX1S PLC on my site which i suspect has a failed output but i just need to confirm that this is the actual issue. The output is Y0 and is  running a small little paddle mixer in 2 different options, either in constant or pulsed Both of these options are selectable through the GOT100O HMI. When i select the pulsed option the output Y0 light comes on but nothing happens. What should happen is that the output comes on and turns on a relay which in turn is giving an inverter a run signal to run the motor for the paddle for 3 milliseconds as the machine doses and then stops. The machine is dosing as normal but the paddle does not pulse.

 When i select the option to run the paddle  on constant the relay pulls in and the inverter runs with no problem which tells me the relay and inverter are both fine.

When i switch back to the pulsed option and i put a piece of link wire between COM 0 and Y0 and mimic a pulse signal the relay pulls in and the inverter runs and the paddle pulses as it should. Everything else on the circuit looks ok and i have checked all connections for tightness, and there are no error messages on the screen and nothing is disabled or bypassed. The guys have told me that before it stopped working completely it would run for a while and then stop and start intermittently.  

Does this point to a failed output?

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Does the output light come on when in pulse mode?

If it does, it's more than likely the output is worn out.

 

You PLC is very old and the output has probably done millions of operations.

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Posted (edited)

There's your answer then :)

You can put a volt meter on the Y0 terminal and check whether there is anything there when it pulses.

If it's missing or intermittent then the output internal relay is failing.

Edited by Ron_S

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And in pulse mode you turn on Y0 for 3ms ?!

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Hi RON_S

I made a mistake the output light does not turn on on the Y0 output when in pulsed mode. But it does turn on when i select constant mode. When i go back and select pulsed mode and measure between Y0 and Com0 I have 24vdc. I am no confused if i have 24vdc at this then should it not be running? When i link it out again with a piece of wire between Y0 and Com0 the paddle runs but am i not just mimicking the constant signal by doing this?

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Posted (edited)

I think, that Y0 is fine.

You just control it the wrong way.

You can not run relay output for just 3ms.

I do not recall right now what is the ON time for Fx series relay outputs, but i assume 10-12ms.

It is normal to get 24V if com0 is connected there and the load is on Y0 and it's other end to GND.

You have potential trough the load when the PLC relay is open(Y0 off)

Edited by glavanov

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If the led output light is not coming on when in pulse mode then something is inhibiting it in the program.

I think you are wrong with the pulse timing, 3msecs wouldn't be enough time to energise the external relay.

 

You have to find out the correct procedure to run in pulsed mode

 

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Posted (edited)

This is from Fx1S hardware manual

for relay output type

Response time 
(approx.)
OFF ➔ ON 10ms
ON ➔ OFF 10ms

Edited by glavanov

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Posted (edited)

That is the wiring schematics, not the plc program.

If the relay on Y0 is the only connection to the inverter then maybe the pulse time is set on the hmi.

There most probably should be a way to alter the on off time.

Edited by Ron_S
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