high range ir transceiver.

[HIREN DAVE]

Hello,

I want to design such a circuit that can detect obstacle with range of min. 4 to 5 meter using IR. is it possible?? any suggested components??


thanks..

 

[Fabien]

I'm not sure. With a few meter, the light from IR will be refracted everywhere. Even if you wait for the pulse it may takes a few ps. Try with ultra sound sensor if you can, it's a better way for the range of meters.

 

[chuckey]

So you would like to make an IR radar, i.e. point it at something and it will say if its in the way? Like a collision detector for a car? Light travels at a very high speed, so a reflection from a target 4m away will take 13 nanoseconds to return. This means that you have to operate the IR transmitter extremely fast to capture a reflection and its not a good place to start from. if you use ultra sound, sound travels at 720MPH so the time delay for your target will be 12 mS, which is low enough to be useable.
Frank

 

[jiripolivka]

There are IR laser distance meters that can measure more than 50 meters. Ultrasonic meters achieve up to 15 meters and are cheaper. The simplest system you can make using acoustic pulses you can hear, with one or two loudspeakers and an oscilloscope. This can show reflections of objects up to 10 m away. Similar devices are now being made for blind people.

 

[HIREN DAVE]

actually, i m developing a system for blind persons... I want to use IR because less costly than ultrasonic.
how can i make a system with acoustic pulses that can hear, with one or two loudspeakers and an oscilloscope? That can show reflections of object?

 

[Fabien]

sure it can! You need to know what's the best frequency for your receiver loudspeaker. It can have a kind of a resonnant frequency. Try to do some short pulses of a sinewave and measure the signal out of the receiver. You should get the same signal with a phase delay. Sweep the frequency to find the best one.

 

[jiripolivka]

actually, i m developing a system for blind persons... I want to use IR because less costly than ultrasonic.
how can i make a system with acoustic pulses that can hear, with one or two loudspeakers and an oscilloscope? That can show reflections of object?

Many blind persons actually use acoustic clicking and echo to detect objects around. It works like with bats. For experiments the oscilloscope is best to see the delayed sound pulse returns.

IR may b e less costly than ultrasonic devices but you will have to filter out the ambient light which overwhelms the detection electronics.

I did experiments with ultrasonic transducers at 40 kHz, one to transmit and one to receive, and an oscilloscope for tuning. The same good results were with two small loudspeakers and acoustic pulses. I had to modulate the IR emittter with 1 kHz pulses to enable the receiver to detect returns. As I used a LED, the result was poor. You can use an IR laser, but its light is dangerous to human eyes and can blind a person forever if the >5 mW IR power hits an eye.

 

[Fabien]

well... does it matter if the person is already blind??

 

[jiripolivka]

well... does it matter if the person is already blind??

A blind person with a laser can blind forever a normal person without him/her knowing it.

 

[HIREN DAVE]

ok thanks..
any easy and cheap way to perform this obstacle detection for long range? i mean any direct transceiver IC is available or not?? I want to make things easy and cheap, so that any blind person can buy it. I don't want to make money from this project.

 

[KerimF]

I never worked on such project but, in my opinion, it should be acoustic, generally speaking.
And to make it low-cost, the frequency of the sonic pulsed waves could be within the audio spectrum (likely its upper part).
The written program of its MCU decides if the project will be practical or not. Also its average power consumption needs to be relatively low since it works on battery.

 

[jiripolivka]

ok thanks..
any easy and cheap way to perform this obstacle detection for long range? i mean any direct transceiver IC is available or not?? I want to make things easy and cheap, so that any blind person can buy it. I don't want to make money from this project.

To generate acoustic, ultrasonic or IR pulses, a 555 is a good choice. To evaluate the reflections from surrounding objects, the electronics may be more complex.
I have noticed that many blind people actually click by their mouth or use keys etc. to generate short sound pulses, then train their perception to detect fixed or moving objects around. They have better hearing than we do, and can use the sounds like sight.
In my opinion, if you offer a simple sound clicker to a blind person, it may be a good start for him/her to try listen for walls, people, etc.. If you make something too complex, it may be too expensive.
A sound clicker also alerts other people that someone cannot see them, and avoid collision. I use to assist blind people anywhere in the world, and had many nice encounters. Also, most told me nobody cares. This cannot be replaced with "a device"