next topic »

[on:]

I have just started playing with using a remote to control my DIY audio gear. I have started with trying to just get the remote to turn the gear off & on, in my playing around I have noticed the the IR receiver is very sensitive (read too sensitive) and turns on & off at the drop of a hat. I bought the Vishay TSOP2138 which I thought was the go but it looking like if I connect this thing up to me stereo it will be turning on & off at the drop of a hat.

Any suggestions on how to deal with this problem?

[Reply #1 on:]

Did you use a cap and resistor on the 5V/GND lines per the datasheet?

Is the sensor in direct sunlight?

[Reply #2 on:]

Hmm, probably not I'll have to have another look at that data sheet, thanks

[Reply #3 on:]

I did what was suggested & read the data sheet & it call for what I think is a polarized 4.7ufcapacitor to be put across the power & ground terminals, my question is what type of capacitor would be the most suitable for this application.

[Reply #4 on:]

A ceramic capacitor should be fine. You should feel free to experiment with different values or multiple caps in parallel, but remember that the datasheet recommends .1uF as a starting point.

When a certain type of capacitor is recommended you should expect that the datasheet will state that explicitly.

[Reply #5 on:]

I don't think you can use the output of that receiver raw, its just the demodulated signal.  The microcontroller should be looking for valid code patterns from that pin. What IR transmitter are you using?

[Reply #6 on:]

A ceramic capacitor should be fine. You should feel free to experiment with different values or multiple caps in parallel, but remember that the datasheet recommends .1uF as a starting point.

When a certain type of capacitor is recommended you should expect that the datasheet will state that explicitly.

The data sheet says 4.7uf?

Thanks

[Reply #7 on:]

The data sheet says 4.7uf?

I might be looking at the wrong datasheet; it says TSOP2138 is discontinued and replaced by another part but isn't clear what that part is (says "TSOP21..."). Anywho, just try something. What I did is set up a little circuit with a transistor to blink a LED when the output pin showed high and then adjusted values until it blinked the least. I really only had problems with the blinkiness when it was in direct sunlight.

I don't think you can use the output of that receiver raw, its just the demodulated signal.  The microcontroller should be looking for valid code patterns from that pin. What IR transmitter are you using?

Even with an encoded a message over that modulated frequency the receiver will screw things up if its frequently showing active signals at random.

[Reply #8 on:]

Even with an encoded a message over that modulated frequency the receiver will screw things up if its frequently showing active signals at random.

That's not how I read the datasheet - if there is a modulated 38kHz carrier coming it the auto-gain-control in the chip will adjust to the signal level and reliably toggle the output according to presence/absense of carrier.  With no 38kHz input it will turn up to maximum gain and be very sensitive to noise - hence some random transitions.  So long as there is enough redundancy in the codes you send the change of random transistions being mistaken for an actual command can be made vanishingly small.

Think of a radio tuned to a station - lots of signal, very little noise - between stations the gain is turned up and the noise becomes dominant.  IR receivers are no difference in principle to a radio receiver.