Selection of infrared components and calculation

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Discussion Overview

The discussion revolves around the selection and calculation of infrared components for a sensor control application using a PLC. Participants explore the use of phototransistors for detecting infrared signals and the necessary amplification to interface with a 24V PLC system.

Discussion Character

  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant seeks advice on using phototransistors for infrared detection and amplification to control a PLC.
  • Another participant notes that phototransistors operate differently than standard transistors, specifically mentioning the absence of base current (Ib) as it is controlled by incident light.
  • A participant shares a resource link for application notes on common collector and common emitter phototransistor circuits.

Areas of Agreement / Disagreement

There is no consensus on the best approach for amplifying the signal to 24V, as participants have not fully explored or agreed on the methods of amplification or the specific configurations to use.

Contextual Notes

The discussion does not address the specifics of signal amplification techniques or the implications of using different components, leaving some assumptions and calculations unresolved.

Who May Find This Useful

Individuals interested in sensor control applications, PLC interfacing, and infrared component selection may find this discussion relevant.

StealthRay
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Hello,

Can any experts give me some advice on the selection and calculation of infrared in control.

I want to do a simple sensor control by PLC which utilize the infrared.When the receiver detects the infrared from the transmitter, the signal will trigger the PLC for some form of control.

At this point, photo sensitivity, wavelength, noise is not of my concern.However,I want the range of detection to be about 30-45 degree and at the length of about 1 metre.

I thought of using phototransistor because i saw some receiver circuits using it. My problem is how do I amplify the signal to 24v so that the PLC can recognize it. Is phototransistor works the same way as the transistor?Is the calculation similar in obtaining the Ic, Ib, and Vce?

Can the phototransistor works like the transistor and amplify the output voltage Vc to 24V?
If not should I use another transistor to do that?Or should I use an op-amp to do that?

Any advice is very much appreciated.

Thank you.
 
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StealthRay said:
I thought of using phototransistor because i saw some receiver circuits using it. My problem is how do I amplify the signal to 24v so that the PLC can recognize it. Is phototransistor works the same way as the transistor?Is the calculation similar in obtaining the Ic, Ib, and Vce?

Yes, except that there is no Ib as it is controlled by incident light.
 
Here's a little application note for common collector and common emitter photo transistor circuits: "www.fairchildsemi.com/an/AN/AN-3005.pdf"[/URL]
 
Last edited by a moderator:
Thanks a lot.
 

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