Any idea on Photo sensor's connection?

[Ezechieltey]

I am currently doing a task. I have a photo sensor with 3 terminals -> Signal wire and another 2 wires for powering. Note that the 2 powering is connected to a voltage source, and I want to use the signal wire to initiate an LED so that the LED lights on/ off indicated whether there is a signal detected or not.

Now this is the part, how can I use the Signal wire? Is it relevent to connect the Signal wire to a relay which will initiate the LED circuit? What type of relay should it be? Or there are other ways?

Note : Definately not PLC, that is too costly and we don't need that for such simple application do we.

 

[KMoffett]

Manufacturer and part # for the sensor...or a link to the datasheet?

Ken

 

[Ezechieltey]

I might hav to be back to my office and check it 5 days later. Well I guess it is not so nessessary to know the part number anyway. The photo sensor should be quite common. Black in colour with a small led indicated on the sensor itself, with 1 black wire consist of 3 minor wires in which 1 is N (neutral), S (signal), another one cant remember.

Normalky for a machine with higher complexity the sensor's S terminal will be connected to the PLC input. Now instead of using PLC I wanna use something else because PLC is too costly and too "useful" for my simple application.

 

[KMoffett]

In order to know how to interface the sensor to something other than a PLC, you need to know if the output is HI or LO on sensing the light/no-light condition. Also how much current the output is capable of providing.

Ken

 

[Ezechieltey]

Hmm, I don't think I need a high voltage at this point. The sensor itself is small, around........0.8cm^2 in area. Is too difficult for me to tell you the detail info since I am not in my office. But roughly, what kind of interfaces can be used to connect the Signal wire to the external LED indicator? Is relay possible?

 

[KMoffett]

Again, without the spec's it is impossible to tell. I could make all kinds of guesses about circuits that would work, if my guesses were correct...but that wouldn't be giving you a usable answer.

Ken

 

[Ezechieltey]

Okay I will check it out next week.

 

[KMoffett]

I'll be here.

Ken

 

[Ezechieltey]

Okay Ken I got it. The photo sensor is Sunx PM-L44P. Now any idea?

 

[john1]

https://www.electro-tech-online.com/custompdfs/2008/12/ds_63100_3701_en_pm.pdf

 

[Ezechieltey]

Yea i know, but I need a suitable relay to connect with it and to link the relay with another circuit.

 

[KMoffett]

Yea i know, but I need a suitable relay to connect with it and to link the relay with another circuit.

It looks like your sensor can supply 50mA for a relay. The sensor will run on any voltage between 5VDC and 24VDC. What voltage are you supplying to your sensor. What is the voltage and current of the circuit that you want the relay to switch. That should give us all the info needed to select a relay.

Ken

 

[Ezechieltey]

Voltage supply to my sensor should be 24VDC. The voltage for relay to switch to another circuit should be designated at around 2-3VDC and 15-20mA to go trough a LED so that it can light/dark out in reference to the photosensors.

I currently have a design in which a 24VDC supply is provide to both Relay switch circuit and Photosernsors. Voltage at the relay circuit part will be shared out by resistor orientated in series with the LED so that LED can have low voltage supplied.

If you need my design diagram i will draw one for you.

 

[KMoffett]

A drawing would be nice. At this point we looking for a 24 volt relay, with a coil resistance of less than 480Ω, or power consumption of less than 120mW (same spec' in different terms). We're getting there. The last two requirements are the switch contact configuration (the drawing will tell me that), and the physical case/connections type.

Ken

 

[Ezechieltey]

There are some errors occur while displaying/attaching the file. So let me try to explain the circuit by words :

Suppose I have the circuit set up with sensor (24V,50mA) goes in parallel with a relay (24V, 480 ohm ) + a LED (2-3V, 15-20mA, power consumption 30-60mW).

2 questions from the above situation :

Is the design relevant? LED would not be functioning or either it is damaged isn't it? In this case I need to add a resistor?

Is the coil's self resistance going to affect the resistance of the secondary circuit? (note : primary circuit = sensor ; secondary circuit = LED)

 

[kchriste]

If you just want to light a LED, then all you need, in addition to the sensor and power supply, is a LED and a resistor. You won't need a relay.

 

[Ezechieltey]

If you just want to light a LED, then all you need, in addition to the sensor and power supply, is a LED and a resistor. You won't need a relay.

Can the signal wire sends current to light the LED? What I know is it does not......

 

[kchriste]

Yes, since the sensor can supply 50ma, it can drive a LED at 20ma directly:

 

[Ezechieltey]

Yes, since the sensor can supply 50ma, it can drive a LED at 20ma directly:

Ignore VLED? any reason behind? Since the line at LED + R is in series at 24V shudn't both components share out the 24V (I thought we need atleast 2-3 volts to drive forward bias in LED)?

 

[kchriste]

All I meant was that I ignored the LED voltage drop in the resistor calculations that I posted because I didn't know which LED you were using.
Different color LEDs have different forward voltage drops. A white LED could have a 3.5V drop where as a red one maybe 2V drop. So, for a red LED (2V) and a 1.2K resistor with a 24V supply, you would get (24-2)/1200 = 18.3ma current. If it was a white LED (3.5V) and a 1.2K resistor with a 24V supply, you would get (24-3.5)/1200 = 17.1ma current. You are not going to notice the difference of 1ma in LED current anyway and both values are within the spec of most LEDs.
BTW, I would go with the lowest supply voltage that is convenient, to minimize power dissipation in the LED dropping resistors.