Infrared Emitter and Detector Question

In summary, The speaker has two questions about detecting infrared, one about the use of a cadmium-sulfide detector and the other about building a circuit for an infrared emitter. They mention using a 9V battery and a 50 Ohm resistor for the circuit. Another speaker suggests using transistors for better battery life and mentions using PIN photodiodes as detectors. The original speaker is concerned about the response time of the CdS detector and it is suggested that it needs to be in complete darkness to work effectively.
  • #1
latinerd
3
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
 
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  • #2
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).
 
  • #3
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.
 

FAQ: Infrared Emitter and Detector Question

What is an infrared emitter and detector?

An infrared emitter and detector are electronic devices used to emit and detect infrared radiation. The emitter converts electrical energy into infrared radiation, while the detector converts infrared radiation into an electrical signal.

How does an infrared emitter and detector work?

The emitter uses a filament or LED to convert electrical energy into infrared radiation. The detector uses a photodiode or phototransistor to convert infrared radiation into an electrical signal. When an object is placed in front of the emitter, it reflects or absorbs the infrared radiation, which is then detected by the detector.

What are the applications of infrared emitters and detectors?

Infrared emitters and detectors have a wide range of applications, including remote controls, motion sensors, temperature sensors, and night vision cameras. They are also used in industrial and scientific applications such as gas monitoring and spectroscopy.

Are infrared emitters and detectors safe?

In general, infrared emitters and detectors are safe to use. They emit and detect radiation in the infrared spectrum, which is lower in energy and less harmful than other types of radiation such as ultraviolet or X-rays. However, it is important to follow safety precautions and guidelines when using these devices.

How do I choose the right infrared emitter and detector for my project?

When choosing an infrared emitter and detector, consider the wavelength range, power requirements, and sensitivity needed for your project. It is also important to select a reliable and reputable brand and to consult with experts or do thorough research to ensure that the devices meet your specific needs.

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