I plan to use an IR transmitter and receiver with 24V supplied by the PLC, I'd then attach the output from the transistor to one of the PLCs digital inputs.
Was wondering whether the circuit included would work okay? If not how can I improve it?
Cheers

 

The voltage at the collector of your transistor will always be at 24v and the emitter will always be at ground. Why is the transistor there?

 

The voltage at the collector of your transistor will always be at 24v and the emitter will always be at ground. Why is the transistor there?

Would I not require a level shifter? Or would the digital input pin still read it without ?

 

Would I not require a level shifter? Or would the digital input pin still read it without ?

Your circuit is not level shifting anything.

 

Is the 24v turning on and off to send some digital signal to the PLC, or is it an analog value between 0-24v? Or is there a 4-20mA signal?

Then your output is to a logic level (0-5v or 0.3.3v) and please specify if it is digital or analog.

 

I'm supplying a constant 24V to the IR LED and photodiode to sense movement. I want to send a digital high input to the PLC when movement is detected.

 

What is missing is a resistor in the collector circuit.
Add a 4.7 k resistor there and take the signal off the collector.

What kind of physical range are you expecting from this sensor?

 

thanks will do

not expecting anything spectacular as far as range goes, its just for proof of concept at the moment

 

You could connect the collector of the 2N2222 to the opto isolator in the PLC input terminal.
What do you need the LED indicator for, there is normally a status LED in the PLC input.
Does the PLC sink or source inputs?

 

You'll be lucky to get an 8" (20 cm) range. Ir sensors like a garage door opener safety system pulses at 38k Hz and the receiver has a high gain amplifier that filters out all signals that are not 38kHz.

 

You could connect the collector of the 2N2222 to the opto isolator in the PLC input terminal.
What do you need the LED indicator for, there is normally a status LED in the PLC input.
Does the PLC sink or source inputs?

It's not an LED indicator, it is his IR emitter to sense motion (beam interruption) to his photodiode.

 

Missed that.
@db000 what PLC is it, and input module?

 

Using the Siemens S7 1215C DC/DC/DC, which sinks inputs

 

Inputs may be pulled high or low, but they don’t sink or source. Whatever drives the input, sinks or sources.

 

Inputs may be pulled high or low, but they don’t sink or source. Whatever drives the input, sinks or sources.

Umm, PLC module inputs are different than the input on a CMOS chip.

 

Using the Siemens S7 1215C DC/DC/DC, which sinks inputs

If the PLC sinks, then revise the circuit so that the circuit sources, e.g. use a PNP 2N2907 etc.