Infrared Emitter and Detector Question

  • Thread starter Thread starter latinerd
  • Start date Start date
  • Tags Tags
    Detector Infrared
Click For Summary
SUMMARY

The discussion centers on the use of cadmium-sulfide (CdS) detectors for infrared (IR) applications and the construction of an infrared emitter circuit. It is established that CdS detectors may not effectively detect infrared in complete darkness due to their broad spectral response and slower response times. For optimal performance, PIN photodiodes are recommended as they align better with the IR spectrum and offer faster response times. Additionally, the calculation for the resistor value in the infrared emitter circuit is confirmed, suggesting a 50 Ohm resistor is appropriate for a 9V battery setup.

PREREQUISITES
  • Understanding of infrared emitter specifications, including forward voltage and current.
  • Knowledge of resistor calculations in electronic circuits.
  • Familiarity with photodetector types, specifically cadmium-sulfide and PIN photodiodes.
  • Basic electronics concepts, including current-to-voltage conversion using op-amps.
NEXT STEPS
  • Research the specifications and performance characteristics of PIN photodiodes for infrared detection.
  • Learn about current-to-voltage op-amp circuit configurations for photodetector applications.
  • Investigate alternative infrared detectors and their suitability for specific applications.
  • Explore battery life optimization techniques for electronic circuits, particularly in emitter designs.
USEFUL FOR

Electronics enthusiasts, hobbyists building infrared sensor circuits, and engineers designing detection systems requiring efficient photodetectors.

latinerd
Messages
3
Reaction score
0
Hi nerdy geeky folks,

I have two questions:

1. can a regular cadmium-sulfide detect infrared in a complete absence of light (but a beam of infrared)? if not, what can be used to detect infrared (for a beam break sensor)?

2. I just want to make sure that I am building the circuit right. So, I am building an infrared emitter whose forward voltage is 1.3-1.7V, reverse voltage is 5V, and continuous forward current is 150mA (according to he specification provided by Radioshack). I am using a 9-V battery as a power source. Since 9V-1.3V=7.7V and 7.7V/150mA=51 Ohm, I should use a 50 Ohm resistor, right?

This will help me tremendously, and I appreciate it!

HJ
 
Engineering news on Phys.org
The resistor value sounds right. You'd get much better battery life by using 3 C cells and making a 150mA current source with transistors, but you can do it with the 9V battery and dropping resistor.

As for the detector, I haven't used CdS detectors, but you should be able to compare the datasheet spectra for the emitter and the candidate CdS detector to see how they match up. I've used PIN photodiodes for detectors, and they match up well with the IR spectrum. I'm usually concerned with the speed of the photodector response, so that's why I use reverse-biased PIN photodetectors (in a current-to-voltage opamp circuit configuration).
 
I'm fairly sure, without looking it up, that CdS detectors have a very broad range of frequencies it can see well. So will have to have it dark of other light to get a good change in resistance. And like Bekerman implied, CdS detector response times are kinda slow.
 

Similar threads

IR Phototransistor Emitter and Detector Questions
  • · Replies 3 ·
Replies
3
Views
19K
Graduate Avalanche photon detectors
  • · Replies 0 ·
Replies
0
Views
909