Encoder and decoder ic problem

there is a problem to transmit data from transmitter circuit. At the receiver side the vt pin of decoder ic(HT12d) is high, when transmitter circuit is powering up, but the data pin of decoder ic is kept high. although at transmit side we send zero signal. plz help

Not enough information.

We need to see how you have them wired together, please post a schematic.

Brian.

receiver side circuit

In this circuit diagram another circuit also connect this receiver circuit..

the transmitter circuit diagram is
transmitter section.pdf

The receiver should work OK but the transmitter circuit is suspect.

First point: make sure the transmitted data rate and receiver data rate are the same.

Second point, the transmitter data inputs have internal pull-up resistors but your external transistors also pull the inputs to VCC, you need to pull the inputs low, not high to set a data pattern on them.

Brian.

for data rate the value of resistor is chose from datasheet. i think it will be ok.

I can't understand how external transistor is pull the inputs to vcc. As we provide no signal at base of transistor.

can you explain me how to pull the inputs low. if this cause error



Thank you sir the problem is solved. I made a mistake because by default encoder AD(data pin) is high. And it will be zero when we externally grounded