If the input signal travels 100 meters, is it better to connect it to the positive pole or the negative pole of the optocoupler?

sky999

If the input signal travels 100 meters, is it better to connect it to the positive pole or the negative pole of the optocoupler? [Copy link]

If the IN1 wiring length is 100 meters, is it better to connect IN1 like this, with the negative pole for 100 meters, or is it better to pull the 12V positive pole for 100 meters?

I'm just curious, I want to know if the 100m range will be attenuated to the point where it cannot be used normally.

张杰克

Neither the positive nor the negative pole is good. You have to consider the current drive, 10k resistor is obviously too large. Or you can use 485 drive.

maychang

The IN1 line is 100m long, so where does the 12V power supply used by the optocoupler come from? Obviously, the 12V power supply line also needs to be 100m long, otherwise the current in the optocoupler cannot form a loop.

qwqwqw2088

It will definitely decline.

Inside the optocoupler is a bidirectional photosensitive diode that conducts when there is light. The stronger the light, the smaller the resistance. When there is no light, it is cut off and no power is supplied.

You can try Changxing

sky999

Posted by Zhang Jieke on 2019-11-1 10:19 Neither the positive nor the negative pole is good. You have to consider the current drive, and the 10k resistor is obviously too large. Or you can use 485 drive.

No, this assumes that a sensor is 100 meters away and inputs a signal to the circuit board.

sky999

maychang posted on 2019-11-1 10:40 The IN1 line is 100m long, so where does the 12V power supply used by the optocoupler come from? Obviously, the 12V power supply line also needs to be 100m, otherwise the current in the optocoupler cannot form a loop. ...

Yes, I mean to simulate a sensor input signal 100 meters away, that is, the positive and negative poles of 12V follow the signal line for 100 meters.

sky999

qwqwqw2088 posted on 2019-11-1 10:50 It must be attenuated. Inside the optocoupler, there is a bidirectional photosensitive diode. When there is light, it is turned on. The stronger the light, the smaller the resistance; when there is no light, it is cut off and no power is supplied. ...

Ha, I mainly saw a surveillance camera installed near us. He used very thin wires, roughly estimated to be 0.3 square meters, connected to 12V and walked 30 meters to connect to a surveillance camera. The surveillance camera actually worked, so I was curious.

maychang

sky999 posted on 2019-11-1 10:54 Yes, I mean to simulate a sensor input signal 100 meters away, that is, the positive and negative poles of 12V follow the signal line for 100 meters

Since there are two wires, it doesn’t make sense to ask “is it better to connect to the positive or negative pole of the optocoupler?” It is the same whether it is connected to the positive or negative pole.

maychang

"I'm just curious. I want to know if the 100-meter range will be attenuated to the point where it cannot be used normally."

As long as the current is not too large, it can be used normally. What affects the use is the resistance of the wire. The voltage drop of the resistance makes the voltage at the load end lower than that at the power supply end. Whether it can be used normally depends on how much voltage drop you can accept.

qwqwqw2088

sky999 posted on 2019-11-1 10:55 Ha, I mainly saw a surveillance camera installed near us. They used very thin wires, roughly 0.3 square meters of wire, connected to 12V and walked 30 meters to connect a surveillance camera, ...

Monitoring line?
It depends on what kind of line it is. Generally, the line requirements are: 75-3 for indoor use: the transmission distance is controlled within 150 meters; 75-5: the transmission distance is within 300 meters; 75-5 or 75-7 is generally used outdoors, and the transmission distance is controlled within 300 meters

chunyang

The two are completely equivalent. As for whether the attenuation causes a problem, it depends on your pre-stage driver. If the driving current is sufficient, there will be no problem.