Connect with us

How to increase range of IR Emitter

Discussion in 'General Electronics Discussion' started by BlueCerealBox, Oct 12, 2015.

  1. BlueCerealBox

    BlueCerealBox

    27
    0
    Sep 30, 2014
    Hi ,

    I am currently doing a school project. For one of my subsystems , I am trying to use a IR sensor and emitter to build a distance sensor attached to a buzzer such that the buzzer beeps louder and with a higher frequency the closer an object is to the sensors. However, I am only allowed to use components supplied from my school lab itself.

    I am using a TIL38 IR Emitter and a TIL81 IR detector. I have connected the 2 according to the circuit in the image attached to test out the range. When I tried it out , the range was only a few milimeters. I measured the voltage drop across the detector , and realized that it only decreased by a very small amount when the emitter was brought closer , probably about a few hundred μV.

    I tried decreasing the resistances in the circuit, which did not help too much. I have researched online and found that one possible method is to set your supply to have a duty cycle of 10% and increase the current supplied , such that it fires short bursts of the max forward current of the emitter ( Which is about 150mA from the datasheet) . So I tried cranking up my voltage supply to 9V and found that the range increases by only a few cm.

    Is there any way to further increase this sensing distance? To maybe about 1.5m?

    Thank you.
     

    Attached Files:

  2. AnalogKid

    AnalogKid

    2,299
    647
    Jun 10, 2015
    Yes, you can crank up the emitter current and reduce the duty cycle to compensate, and the system distance will increase. But that method has limits, and a very bright emitter is dangerous, especially if you can not see it directly.

    Is your project based on the IR energy being reflected off of a random object? If so, 1.5 m will be very difficult to achieve reliably because the IR receiver is seeing everything around it, not just the reflected energy from the emitter. The common solution is a bit more complex. You modulate the IR emitter with a high frequency clock signal. It his way its output is very different from other IR sources such as body heat, lights, etc. Then the receiver has a detector circuit that looks for this particular frequency. That solves thee interference problem, but not the distance problem. Most common surfaces such as clothing, books, etc. do not reflect well. I would not be surprised if only 1% of the incident energy were reflected back toward the source. Sure you can add lots of gain to the receiver, but that increases interference.

    Are there other conditions about the environment or the objects being sensed that can be used to manipulate things to your advantage?

    ak
     
  3. BlueCerealBox

    BlueCerealBox

    27
    0
    Sep 30, 2014
    Actually yes. My project is based on the IR energy reflecting off random objects. I am actually trying to build an aid for the blind as my project , this distance sensor would serve as a method of basic navigation around public areas. I understand that black surfaces do not tend to reflect IR rays as well, so this does generate a few problems. But before that I'm just trying to increase the range of detection.
     
  4. duke37

    duke37

    5,231
    718
    Jan 9, 2011
    To increase distance, you will need to concentrate the light in one direction.
    You can use a parabolic mirror or a Frenel lens. The mirror can come out of a torch and the lens can be bought cheaply.
    Using a lens at each end and coded signals, distances of several km have been obtained.
     
  5. AnalogKid

    AnalogKid

    2,299
    647
    Jun 10, 2015
    For a *reflective* distance sensor with both the emitter and receiver co-located?

    ak
     
  6. duke37

    duke37

    5,231
    718
    Jan 9, 2011
    I was just commenting on the limits of distance which could be obtained. I have not studied the effect of reflection but much work has been done on reflection of radio waves from the moon, it can be done with a high gain aerial for transmission and reflection.
    To measure distance using reflection, an array of detectors to measure angle of dangle may be necessary. Time of flight would be difficult to do.
    How do measuring lasers or speed cameras work?
     
  7. AnalogKid

    AnalogKid

    2,299
    647
    Jun 10, 2015
    Seems like a lot for a blind person to carry around. OTOH, think ultrasonic. Polaroid perfected ultrasonic distance ranging in the 70's, it is standard equipment on many cars, and Chinese modules are available on ebay for a few dollars. Unless you have other reasons for focusing on IR, that probably is a better place to start.

    ak
     
  8. Tinker Unique

    Tinker Unique

    22
    2
    Dec 1, 2014
    NOT relevant to this issue, but for another system.... A set of lenses from a pair of binoculars will increase the range of the receiver. ( sometimes found at Goodwill, or ?) Can be used as an intrusion alarm.
     
  9. BlueCerealBox

    BlueCerealBox

    27
    0
    Sep 30, 2014
    I'm focusing on IR due to the constraints of the project, if you look at the component list that I attached in the first post , there's not much else to use. i wanteed to make distance sensing a main feature of the project.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-