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TSOP4838 IR receiver

Although some of the components featured on this blog have been purchased and used in projects, there is a lot of stuff I really don't know why I bought - a bit like storing nuts for a rainy day I guess, or maybe just because I'm nuts.

Anyway I stumbled across a packet of weird looking bulging three prong components in the plastic tubs of goodies and identified them as TSOP4838 IR receivers. I'm guessing they could be useful, but for now I just wanted to test them and make sure that they did what is advertised on the packet - receive IR signals. 

I originally built a circuit which had an LED shining brightly and then flickered a bit when an IR remote activated the TSOP4838, and that was perfectly fine, but it would have been a bit of a fall in complexity after last week's effort!

So I kept poking around the internet and found a more engaging circuit which had two things of interest - firstly the indicator LED was off until activated, and secondly it used a PNP transistor. I have a few packets of PNP transistors but could never see the point of them until now. From the link above comes the following revelation:

"We have use BC557 PNP transistor here, to reverse the effect of TSOP, means whenever the output is HIGH LED will be OFF and whenever it detects IR and output is low, LED will be ON. PNP transistor behaves opposite to the NPN transistor, it acts as open switch when a voltage applied to its base and acts as closed switch when there is no voltage at its base."

Although the internet version of the circuit has both a receiver and an emitter (provided by a 555 timer set at 38kHz), I thought I'd be a bit lazy and just point a TV remote at the receiver and see what happened. Also now that I can see that the circuit works well, it can be easily used to check if I need to replace the batteries in a remote control.

Here's the circuit on fritzing:

And here it is in "real life", plus a video of it in "action".