Infrared remote control range

Hi,
I am building an infrared remote control for my project. I'm using TSOP1236. I connect an oscilloscope to the Vout of the TSOP1236. From my visual, there is a waveform on the oscilloscope screen. But the maximum distance before I lose sight of the waveform is 7.5cm or 3 inch. This is very short from what the datasheet said which suppose to be 35m. the current passing through IR LED is more than 0.1A and i also inserted pulse of 36kHz to the IR LED. Eg. i insert squarewave of 36kHz for 560us then nothing for another 560us. and the whole process is repeated again but the range still doesn't increase. the current going through IR LED is quite high and i also inserted pulses of 36kHz not continuous 36kHz. I have done everything said in the datasheet but the range doesn't increase.
Do you guys have any idea to solve this problem?

The TSOP1236 has a fairly narrow wavelength over which it is sensitive - centred over 950nm. What wavelength is your LED?

Keith.

950nm. im using TSAL 6200. The datasheet used this to test the TSOP1236

Are you sure you are modulating the LED fully? It would be worthwhile getting a straightforward photodiode and using that as a double check.

Keith.

i insert this frequency(pls see the attachment) to the IR LED. TSOP1236 is able to pick up the signal. the Vout of the TSOP is correct. but after i move the IR LED away for more than 3inches, the Vout of the TSOP1236 is constant high(active low). i try to using different value of current going through the IR LED but that doesnt seem to have an effect on the distance

Are you sure you are really putting 100mA into your LED? What is your LED drive circuit?

Keith.

this is the transmitter circuit

That looks ok, depending on what the transistor is. I assume the driver is 5V?

I think a photodiode to double check is required. I assume you have double checked the modulation frequency? If you have a signal generator it might be worth varying the frequency to check the device is labelled correctly.

Keith

HOW CAN CHANGE ANY IR REMOTE ADD. VALUE

From your attached scope shot:

10 modulation cycles per 560 uS.

If your modulation frequency is indeed 36 KHz, then your mark-space ratio is actually 280 us on - 280 us off, NOT 560 us; no problem, your IR should show up at longer distances.

OTOH, if your mark-space ratio is really 560 us on - 560 us off, YOUR MODULATION FREQUENCY IS 18 KHZ! No way it will work.

Or is my math wrong?

Anand

It would be fair to check it on some frequencies before you mount the scope permenantly.