Originally Posted by Gundam82

Hey ... all... me again... i got problem in IR circuit... i using PIC16F84A to generates 38Khz carrier... then modulated with the data input.. i using 74HCT132 (NAND schmit trigger ) to modulated the carrier with the data input..... i observe the output at osciloscope... it got noise inside... then the problem is... when send the modulated signal...the demodulated module got signal got output..but very small the signal... and.... the decoder part canot show the result... why ya??????????? :shock:

Firstly, why the 74HCT132?, the PIC program can simply turn the 38KHz ON and OFF itself, try looking at my IR tutorials.

Secondly, the IR receiver - it might need a pull-up resistor from the output pin to 5V - also the transistor probably isn't required, assuming you're using a PIC to decode the signal?. It's also usually essential to have a decoupling resistor and capacitor feeding power to these IC's as well, again, consult my tutorials for details.