IR Distance Sensor

[ikalogic]

wow...that's detailed explanation...thanks. But do I need to include some filter in the receiver circuit as the transmitter is being modulated??

well it depends.. depends on your reciever, if you use a simple photo transistor, you don't need to add a filter, but it will be less imune to light.

if you can use a receiver IC, that have an integrated filter, it the best, but you'll have to modulate the sender to a frequency ranging from 38khz to 42khz or bear this.. (depending on the type of receiver module you use.)

note: i am not talking about expensive sharp modules.. no, i am talking about a componenent slightly bigger than a DIP8 package, with a half sphere shaped side...

 

[Nigel Goodwin]

You might consider a method used in the magazine robot Cybot?.

The technique, which I thought was rather clever, is to send a digital word out, just like you would for IR remote control. The sneaky bit is to send the last few bits (which are all ones's) with gradually reducing power - using different resistors to feed the IR LED. This means the receiver reads back a digital word representing the distance - as reflected bits are ones, and missing bits are zeros.

 

[ericgibbs]

Hi Audioguru,
Thanks for the response.
The orginal posting was for a method of measuring range using IR. Now that further postings have
shown what is really being asked for is some form 'proximity' detection. Which as you know is a whole new
ball game.
For such short 'ranges' the IR method is not the best way. We have no idea what type of objects
the mouse is trying to detect and avoid. I would suggest an acoustic method, that relies on a gated echo
detection time slot technique for detecting objects within a certain distance.

Perhaps ma ge38 can give us more info on his actual project so that we can give answers with context.

Its good to swap ideas with someone who takes the trouble to reply to postings.

Regards
EricG

 

[Nigel Goodwin]

For such short 'ranges' the IR method is not the best way. We have no idea what type of objects
the mouse is trying to detect and avoid. I would suggest an acoustic method, that relies on a gated echo
detection time slot technique for detecting objects within a certain distance.

Actually, IR is fine for short range detection, probably better than ultrasonic which is better for longer ranges - the short range is limited by the time taken for the receiver to recover from the transmitted pulse.

 

[ma_ge38]

Perhaps ma ge38 can give us more info on his actual project so that we can give answers with context.

Its good to swap ideas with someone who takes the trouble to reply to postings.

Regards
EricG

Well, actually I am building a micromouse robot (maze solving robot) that use IR sensor on both left and right side to sense the wall of the maze, so that the robot can move in the center of the path by using PID control. The IR sensor will also be used for mapping the maze. My micromouse is around 80mm in width but the path for the maze itself is around 200mm width, which means I need a IR sensor that can sense more than 50mm. I had seen some veteran build the IR sensor using TSL262R and OPE5594A. But, I hope to build my Micromouse with minimum cost, and that's why I wish to build IR distance sensor using normal IR emitter transmitter which is cheaper.

 

[ericgibbs]

Hi nigel,
Working with 1mHz acoustic transducers, it is possible measure millimetric
ranges with high accuracy. Example, feotal womb scans, internal defects
in steel and thickness measurement of bio-matter build up on underwater structures. [ a previous project ]

I am not suggesting that he should take this route to solve his problem,
only that he keeps an open mind on all the options.

Nice chatting with you, look forward to your response.

Regards
EricG

 

[Nigel Goodwin]

Hi nigel,
Working with 1mHz acoustic transducers, it is possible measure millimetric
ranges with high accuracy. Example, feotal womb scans, internal defects
in steel and thickness measurement of bio-matter build up on underwater structures. [ a previous project ]

I am not suggesting that he should take this route to solve his problem,
only that he keeps an open mind on all the options.

Nice chatting with you, look forward to your response.

Only response is that it's not really an option for hobbiests?.

 

[ma_ge38]

Hi, sorry for disappear for a while as I am playing around with pwm + IR sensor... I managed to increase the range of my IR emitter to around 20cm. Thanks guys for your help!! But now new problem arise... when I connect my simple RC high pass filter to the output of receiver, it seems like I get zero voltage from it...

 

[Nigel Goodwin]

Well the transistor seems liking in any kind of biasing, but why do you want a high pass filter?.

 

[audioguru]

It looks like the transistor is an IR receiver circuit or is a photo-transistor and he is trying to get an output from its input or its base.

 

[ma_ge38]

Well the transistor seems liking in any kind of biasing, but why do you want a high pass filter?.

Because I operate the pwm with the frequency of 38kHz... as I hope can reduce some ambient light effect by doing so.

It looks like the transistor is an IR receiver circuit or is a photo-transistor and he is trying to get an output from its input or its base.

Yearp... I am using some normal photo-transistor as the receiver.

 

[Nigel Goodwin]

Because I operate the pwm with the frequency of 38kHz... as I hope can reduce some ambient light effect by doing so.



Yearp... I am using some normal photo-transistor as the receiver.

Why not use a proper IC for it?, that's the whole point of using 38KHz modulation.

 

[ma_ge38]

Why not use a proper IC for it?, that's the whole point of using 38KHz modulation.

Erm... I would like to reduce the cost of my project to the minimum...

 

[Nigel Goodwin]

Using a proper IC probably would do that, building an IR receiver isn't a trivial task, and everything is already contained in a single three pin IC.

 

[ma_ge38]

Thanks... will try that out and will post the outcome as soon as possible.

 

[audioguru]

The range of your IR distance sensor is only 1/50th of what it could be.
1) You are using an ordinary photo-transistor that is sensitive to visible light. Visible light makes it saturate then it doesn't detect anymore. You should use an IR photo-detector that has a physical filter for reducing visible light.
2) Your photo-transistor is used backwards. You are using its base (its input) as an output. The collector is supposed to be the output then it should have a 38kHz bandpass filter and a high gain amplifier.

I don't know the circuit of your transmitter and the circuit of the rest of your receiver.