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Pimpom
02-02-2011, 08:51 PM
The TSOP1738 seems to be the most popular IR receiver module among robot enthusiasts in India, but it's not available where I live. I've been using the Chinese-made SM0038 (Silan) which is used in many TV kits and is available everywhere. The problem is that I could not find the datasheet for the SM0038 even after searching for hours until my head was swimming.

By trial and error, I found that the SM0038 does not like a 1:1 mark-to-space ratio (equal number of pulses in ON and OFF periods). I've been using it at 8 pulses on, 24 pulses off.

I've been using the SM0038 successfully at distances of up to 10 metres with no-name IR LEDs. Now I want to start using an IR LED & receiver combination with known characteristics. (I also found that the no-name LEDs had an unpredictable directivity. Some focussed their peak emission way off the axis).

The TSOP1738 datasheet specifies minimum period lengths of 10 pulses on, 14 pulses off. Does anyone know from practical experience if it accepts equal on/off periods - such as 16 on, 16 off? This is important for my next design, but I cannot just buy one and try it out because I live in a remote location and have to purchase everything by mail order.

Thanks in advance for any input.