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Topic: TSOP4838 IR decoder - "Random" noise (Read 4516 times) previous topic - next topic

dalich

Nov 12, 2012, 04:46 pm Last Edit: Nov 12, 2012, 04:48 pm by danielNC Reason: 1
I am using a TSOP4838 IR decoder as hooked up below.

Pin 1 - Digital signal in
Pin 2 - Gnd
Pin 3 - +5v

I'm displaying the received codes in the serial monitor and it works fine. until I hook it in my project.  I am than getting many "random" codes that persist even when the IR receiver is completely covered from outside light. I found earlier that if I changed the input voltage to 3.3V that is seemed to lessen the random codes in my application, however I am now trying to change my program over to a mini-pro board and there is no 3.3V pin to pull power from.

Is there something I am missing on this component or it there a better Ir decoder that will work with fewer random codes being received?

Additionally, I am trying to see if I can use a RTC1307 and the decoder on the same input pin (A5). (ran out of I/O pins) This seems to work fine until I have the board running my full application.  I think the IR and RTC codes are properly recognized, however I think that power fluctuation on the board are causing what appears to be "random" codes to appear from the TSOP4838.


Chagrin

Sounds like a decoupling problem. You IR datasheet will suggest a cap and resistor on the IR receiver's lines to reduce noise.

Grumpy_Mike

Yes I can confirm that is what you get when you don't use the decoupling recommended in the data sheet.

dalich

Thank you.  I'll take a look for this info.

Dan

michael_x

Quote
I am trying to see if I can use a RTC1307 and the decoder on the same input pin (A5).

How would that work ? The TSOP uses just one signal pin and does not know about an I2C bus address.

dalich

I added in the .1uf cap and 100 ohm resistor and noticed no difference in filtering noise.

I took power (3.3V) for the TSOP4838 from a separate UNO board and it seems to be running very well,  When I pull power from my project board, I get MANY false and apparently random IR codes.

I may try switching over to the Nano board as it has 3.3v, but I wonder what is causing this....  Could by board be having voltage fluctuations that are giving false Ir codes.  It has multiple blinking LEDs that "may" be drawing too much current?

Let me know is something else comes to mind.  The cap and resistor does not seem to have made any difference.   :)

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