Ladder program on Mitsubishi-type GFX3 PLC turns on LEDs but not contacts

MaxHeadRoom

Joined Jul 18, 2013
28,681
Is the PLC S/W have a monitor mode where you can see the status of the input/output, or the output LED etc?
OK I see you mentioned the output does not light, does x000 show its status.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
28,681
You can test the sensor on its own with a 1k resistor from output to -ve and see if it switches OK, monitor the voltage from -ve to output.
Some have a LED indicator.
.What do you intend on detecting, if just a ferrous target this type would have been a little better than the capacitive version.
Max.
 

Thread Starter

quique123

Joined May 15, 2015
405
So you're saying wire ps(24V+) to the brown wire,

wire ps(-) to the blue wire

and wire a 1k resistor between blue and black (output) and monitor the voltage between blue and black?
 

Thread Starter

quique123

Joined May 15, 2015
405
I tried monitor mode and nothing happens. But the led on the sensor works. When I place a metallic object in front of the sensor, very close, about 1-2cm, the red led on the sensor blinks.

So I think the sensor is fine but maybe the program?

Here is a snapshot of the sensor wiring schematic on the sensor itself:86641EB2-0382-4B46-A4C0-9F60A7C8CD70.jpeg
 

MaxHeadRoom

Joined Jul 18, 2013
28,681
If the PLC has the same monitor as the standard Mitsubishi, then you should see the input status change.
Does the voltage between the Blk and Blue when triggered?
Max.
 

Thread Starter

quique123

Joined May 15, 2015
405
I know but for some reason nothing changes. I didn't Try the voltage change at the terminals. So I should put a 1k resistor between the black and blue?

Because I put a 250 one by mistake between blue and black and it smoked
So I wasn't able to get to the voltage measuring part. Ill try the 1k resistor.
 

Thread Starter

quique123

Joined May 15, 2015
405
OK I tried it again and the 1k resistor is slowly burning up because I can smell it. The 250 ohm from yesterday smoked up quickly obviously but the 1k is heating up enough that I can smell it. Here is the setup and I tested the voltage change quickly and the same thing happens with or without the resistor across, the voltage drops from 24v to 0V.

FE3548EA-DEED-4B6E-8895-DFFFAEA4CE33.jpeg

E6245FD0-E0A1-4BC3-A258-07E111D95175.jpeg
 

MaxHeadRoom

Joined Jul 18, 2013
28,681
1K would dissipate about 1/2 watt on 24v.
Maybe use a 4.7k.
I never meant the resistor in circuit when hooked to the PLC! This was just for external testing of the Sensor!
If it shows switching with no resistor, it sort of implies an internal pull down, which would be unusual, unless you did it connected to the PLC as it has its own internal pull down.
Max.
 

Thread Starter

quique123

Joined May 15, 2015
405
I tested the sensor wired to the plc with the resistor, so ok, my bad. No biggie.

But the problem is that the sensor is indeed switching as shown by both:

the led behind the sensor and
the voltage change from 24 - 0V

The problem then would appear to be my code because according to what I interpret from code by:

-| x0 |-----------------------------------------------(y1)

is that input 0 is open, but if it is activated (by the sensor) then it should light up y1, but that doesnt happen. And x0's led never lights up either.
 

MaxHeadRoom

Joined Jul 18, 2013
28,681
OK test the X0 input manually by connecting to the 0v if sinking input.
It should show a change on the X0 contact in the rung.
Edit: make that connect to +ve if sinking input.
Max.
 

Thread Starter

quique123

Joined May 15, 2015
405
ok so you want me to take a wire from 24V on the PLC (which comes from the PS PLC) and plug it into the x0 terminal to see if it lights up?
 

MaxHeadRoom

Joined Jul 18, 2013
28,681
I presume you are using the PLC supply to feed the sensor, so you connect the 24v on the PLC to the input, just as you would using PB.
Max.
 

Thread Starter

quique123

Joined May 15, 2015
405
Yes I am using that PLC PS as the sensor PS. Ok Ill try it. Btw, what is PB?

Ok I tried it, I connected a wire from 24VDC from the PS to the X0 pin, the LED for that X) pin doesnt light up.
 
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MaxHeadRoom

Joined Jul 18, 2013
28,681
P.B. is Push Button.
Does the software have a Monitoring/Run feature as does the Mitsubishi?
You may be simply in the programming stage?
Do you know which for sure if the inputs you have are sinking or sourcing?
Max.
 
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