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...
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.
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.
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.
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.
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.
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.
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...
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.