Ir object detector

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nevil010

Member
please help me to make a ir object detector with the components attached in the picture.....and please note that the transisster have big bump....it doesnt matter what range it can detect..
 

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nick12ab

Senior Member
What's the 'transisster with big bump'?

It's probably an IR receiver with built-in demodulator in which case it cannot be used as it filters out any signal that isn't modulated on to a fixed carrier frequency. If it's a phototransistor then yes you can.

Are the two LEDs both transmitters or is one a receiver (photodiode)?

Using signal strength would not be reliable. For reliable range detection you would have to send a pulse and timing how long it takes to receive the pulse and I doubt a PICAXE or even Arduino is fast enough for this over short distances.
 
S

srnet

Senior Member
nick12ab said:
What's the 'transisster with big bump'?
For reliable range detection you would have to send a pulse and timing how long it takes to receive the pulse and I doubt a PICAXE or even Arduino is fast enough for this over short distances.
Click to expand...
With light traveling at approx 30cm per nanosecond, you are probably right.
 
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Haku

Senior Member
The 38khz IR sensors can be used for object detection but will require more programming to do so. Here's a couple of sensors on eBay which use this approach by having an onboard IC to generate the 38khz signal for the LED(s): http://www.ebay.co.uk/itm/270675884639 http://www.ebay.co.uk/itm/280887888758

I'm guessing that the potentiometers on the boards are for setting the signal strength going to the LED(s).

A photodiode+IR LED is a much easier way of object detection but can be influenced by ambient light more than the 38khz IR sensor method.
 
erco

erco

Senior Member
There are well-documented techniques for measuring relative distance with just the IR LED and 38 khz receiver shown, based on signal reflectance. Actual distance is very difficult , since the IR reflectivity of surrounding objects varies so much. In most cases, the sensors are purely digital, either they detect the reflected signal or not.

Parallax has several free downloads, using slightly different methods. One sends out a series of increasing intensity 38 khz IR signals, and when the signal is detected, the required signal intensity gives a relative indication of distance. This requires several I/O pins and varying resistors to produce the different intensity signals.

The second method uses less hardware and I/O pins. The receiver is most sensitive at its center frequency of (usually) 38 khz, falling off on either side. By sending a sweep of different off-center frequency signals, one can detect relative distance by noting how far off center the signal can be detected.

Lastly, several of Vishay's special fixed-gain IR receivers have a unique ability to gauge relative signal strength. Check the fourth paragraph at http://www.vishay.com/company/press/releases/2010/100628irsensors
 
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westaust55

Moderator
@Neville010,
When you say you want to build an "Ir Detector"
Do you mean as:
1. A range finder to determine distance like your SRF05 project, or
2. A presence detector like a beam break to detect someone coming through a shop/store door?
 
N

nevil010

Member
Haku said:
The 38khz IR sensors can be used for object detection but will require more programming to do so. Here's a couple of sensors on eBay which use this approach by having an onboard IC to generate the 38khz signal for the LED(s): http://www.ebay.co.uk/itm/270675884639 http://www.ebay.co.uk/itm/280887888758

I'm guessing that the potentiometers on the boards are for setting the signal strength going to the LED(s).

A photodiode+IR LED is a much easier way of object detection but can be influenced by ambient light more than the 38khz IR sensor method.
Click to expand...
hey can u give me schematic
 
N

nevil010

Member
westaust55 said:
@Neville010,
When you say you want to build an "Ir Detector"
Do you mean as:
1. A range finder to determine distance like your SRF05 project, or
2. A presence detector like a beam break to detect someone coming through a shop/store door?
Click to expand...
I mean like the srfo5 proect..itz not working anymore and i dont have any money left...thats why i decided to make one...please help
 
A

AllyCat

Senior Member
Hi,

If by "proximate" you mean "range" (measure distance), then as nick said in #10 it is NOT possible with IR LEDs.

If you just mean "detect" then what is the object, how large is it, what are the ambient light conditions, how well does it reflect IR, and what is the (maximum) distance at which it needs to be detected?

Cheers, Alan.
 
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boriz

Senior Member
10-20 WHAT? mm,cm,inch,feet,cubit,furlong?

WHAT should 'not hit the walls' ? A small (2 driven wheels + caster) robot perhaps?

Will it work in a maze or in a competition or just on the kitchen floor?

Only one sensor or several? Fixed or articulated?

Details please!
 
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nevil010

Member
10 - 20 cm..A robot which with two geared motor in back and one free roaming wheel in front...it works on normal floor..only one sensor to detect obstacle so it wont hit it....i bought one srf05 and its not working anymore....hippy told me itz broken and i am trying to make one with ir...so it wont cost that much..jimperry's post #14 told that this tenettech.com/product.php?id_product=1620 product will work with picaxe...but i dont know the code for it...can someone please post the code
 
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