# 2 wire sensor



## don_resqcapt19 (Jul 18, 2010)

Often electronic devices won't play nice with other electronic devices. You need to look at all of the details for both the sensor and the PLC to know if they will work together.


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## MDShunk (Jan 7, 2007)

Just like a switch. How you wire it depends on whether the input card is sinking or sourcing, in which case you'll be using it to switch either DC+ or DCcom.

edit: How do you know 'nothing happens'? Are you triggering the prox properly? "Prox" is a generic term for a great many sensors, and they might need to see a reflector, darkness, magnet, piece of metal, etc.


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## buddhakii (Jan 13, 2011)

Depends on the sensor but most likely it works off a different voltage than the plc. The last one I did I think was something like 5 volts. Had to wire it to a separate relay that is for the sensor.


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## Safari (Jul 9, 2013)

quanchai said:


> Hi guys
> 
> How is two wire proximity sensors wired ?, i got a few of them and my first try was to connect the brown wire to the positive on the plc and the second blue wire to the input of the plc, but nothing happens ?


am just curious to ask what are you expecting to hapen? in other words what should be your output? assuming your plc program is ok

Sent from my HUAWEI Y210-0100 using Tapatalk 2


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## quanchai (Jul 13, 2012)

MDShunk said:


> Just like a switch. How you wire it depends on whether the input card is sinking or sourcing, in which case you'll be using it to switch either DC+ or DCcom.
> 
> edit: How do you know 'nothing happens'? Are you triggering the prox properly? "Prox" is a generic term for a great many sensors, and they might need to see a reflector, darkness, magnet, piece of metal, etc.


This is the Sensor http://hugong.en.alibaba.com/produc...ansducer_infrared_sensor_E3F_5DP2_E3F_5L.html

It is a infrared sensor with only two wires, when i connect it to the plc it triggers the output as programmed but it wont turn off


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## Rollie73 (Sep 19, 2010)

quanchai said:


> This is the Sensor http://hugong.en.alibaba.com/produc...ansducer_infrared_sensor_E3F_5DP2_E3F_5L.html
> 
> It is a infrared sensor with only two wires, when i connect it to the plc it triggers the output as programmed but it wont turn off


 
So it is an infrared, photoelectric sensor and it triggers the input....but the programmed point stays turned on?

Sounds like a programming issue. Is the input programmed to be a momentary sensing switch or does it start a timed counter?


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## don_resqcapt19 (Jul 18, 2010)

Looks like the current that the sensor draws when it is not set is too high to let the input drop out. That is the type of thing I was talking about when I said some electronic devices do not play well with others.
You need to find the details on both the sensor and the input and look at the currents.


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## MDShunk (Jan 7, 2007)

quanchai said:


> This is the Sensor http://hugong.en.alibaba.com/produc...ansducer_infrared_sensor_E3F_5DP2_E3F_5L.html
> 
> It is a infrared sensor with only two wires, when i connect it to the plc it triggers the output as programmed but it wont turn off


Lol, you trigger the input, but your output won't turn off? That's what you said. You either have a programming issue, or an output that is sticking (VERY common). If you're buying no-name sensors from China, your PLC is probably some piece O-crap too. Buy your PLC's from A/B or Seimens, and buy your sensors from Banner, Sick, A/B, or someone you've actually heard of before. WTH.


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## MDShunk (Jan 7, 2007)

quanchai said:


> This is the Sensor http://hugong.en.alibaba.com/produc...ansducer_infrared_sensor_E3F_5DP2_E3F_5L.html
> 
> It is a infrared sensor with only two wires, when i connect it to the plc it triggers the output as programmed but it wont turn off


Lol, you trigger the input, but your output won't turn off? That's what you said. You either have a programming issue, or an output that is sticking (VERY common). If you're buying no-name sensors from China, your PLC is probably some piece O-crap too. Buy your PLC's from A/B or Seimens, and buy your sensors from Banner, Sick, A/B, or someone you've actually heard of before. WTH.


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## quanchai (Jul 13, 2012)

MDShunk said:


> Lol, you trigger the input, but your output won't turn off? That's what you said. You either have a programming issue, or an output that is sticking (VERY common). If you're buying no-name sensors from China, your PLC is probably some piece O-crap too. Buy your PLC's from A/B or Seimens, and buy your sensors from Banner, Sick, A/B, or someone you've actually heard of before. WTH.


The PLC is brand new Siemens LOGO RC12/24 but the sensor is Chinese. the output contact works with no problem when i source a voltage to the input by hand, but the sensor acts like a wire from the Positive to the input, there is a light on the back of the sensor that doesn't turn on

I just want to make sure that the wiring is correct ? because if it is then the problem is probably from the sensor


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## Southeast Power (Jan 18, 2009)

quanchai said:


> Hi guys
> 
> How is two wire proximity sensors wired ?, i got a few of them and my first try was to connect the brown wire to the positive on the plc and the second blue wire to the input of the plc, but nothing happens ?


Try another type of sensor and see if the input reacts the same. Might be a compatibility issue.


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## oliquir (Jan 13, 2011)

input may not be drawing enough current for the sensor to work correctly, add a 1 k bleeding resistor load.


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## quanchai (Jul 13, 2012)

It turned out that i had a parts missing, the piece i had was the infrared sender not the receiver which should be connected to the PLC. The sender goes to the power supply and the other piece(receiver) goes to the PLC, both parts have to face each other.

Any way thanks guys for your support


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## lefleuron (May 22, 2010)

Sounds like you need a pull down resistor. Try 2.3 K ohms, and see if that helps.

Often enough I need to do this, I know the resistance required by heart. Especially if you have a sensor that turns on, but then will not turn off.

Once you get all your parts together, you may still need this. Or at least keep it in mind for the next time...


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