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I am working on a IR based object detector. I understand the basics of how it functions, i.e., 38kHz pulse through an IR LED and read the output pin of the IR sensor.

The problem is that the range upto which I can detect objects is only around 5-10 cms depending of the surface of the object.

I am using a CC2538SF53 micro controller to generate the pulses for the LED. The LED is a Vishay TSAL6100 10 deg 40mW LED. The reciever is a TSOP38238.

Initially I was using the LED directly from the micro controller pins. But the range was even less for that. Now I have connected the LED via a transistor to boost the output and am getting the 5-10 cm range I mentioned above.

Any ideas or help as to how I can boost the range.

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    \$\begingroup\$ The only things I know to do are a) use a higher output LED b) make sure using max current through LED c) use a low duty cycle so you can put more than the rated current to the LED. \$\endgroup\$ – I. Wolfe Jan 8 '15 at 14:43
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    \$\begingroup\$ Can you provide the part number for your LED and sensor, the maximum current the LED accepts and the current you're putting it through? \$\endgroup\$ – Ricardo Jan 8 '15 at 14:43
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    \$\begingroup\$ Also, you can test the LED light output visually using a cheap cell phone or digital camera (expensive ones have IR filters). You can tell high output from low output ones and maybe compare them with a few of your remote controls you have around the house (without much accuracy, that is). \$\endgroup\$ – Ricardo Jan 8 '15 at 14:47
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    \$\begingroup\$ More gain on the IR detector..(what is it?) If you have access to the 38 kHz signal then you could do lockin detection.. \$\endgroup\$ – George Herold Jan 8 '15 at 15:04
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    \$\begingroup\$ How are you detecting the return signal? An LED phototransistor pair should easily see a reflection from more than 10 cm. \$\endgroup\$ – tomnexus Jan 8 '15 at 15:45
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If you provide the part numbers for the IR LED and receiver we can probably provide a more concrete plan to increase the range, but in more general terms:

The two ways I can think of to increase the range involve increasing the output of the LED or increasing the sensitivity of the receiver. The latter I forgot about until George Herold commented about increasing the gain.

So on the receiver end you can increase the gain. The one thing to be careful of here is making sure it still filters out any noise from external IR sources. If you can access the 38kHz pulse, then like George mentioned in the comments, you can use that for lockin detection.

On the LED side the main option is to make sure it is at it's max output. You want to max out the current going through it, and you can utilize a lower duty cycle to increase the current through the LED past it's rating. You could also simply use a higher output LED, the range you're getting seems very low to me so examining the parts you're using might be a good idea.

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  • \$\begingroup\$ I added the part nos. \$\endgroup\$ – Suman Roy Jan 9 '15 at 9:22
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The best you can do with COTS stuff is to use an infrared remote receiver matched to the same optical wavelength as an IR emitter which is pulsed at the receiver's tuned frequency, say 38kHz.

The receiver will comprise everything needed to discriminate against everything but the 38kHz modulated IR carrier from the emitter, and will output either Vcc or 0V when it receives the modulated carrier from the emitter, or the complement when it doesn't.

The gain of the receiver is generally fixed, and in order to increase its detection range a higher power emitter can be used, several emitters can be modulated simultaneously, or the IR beam can be optically collimated at the emitter or receiver end, or both.

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