I have been recently working on a RF operated water pump project. For this purpose i bought a RF RX and TX module which has HT12E and HT12D chips as encoder and decoder.
The D8 (Dout) pin of decoder is latched output and power on state is active low so whenever the circuit is powered off and then turned ON again it automatically gives output in D8 pin and in turn drives the water pump. I don't want that to happen.
In order to eliminate this i thought to use VT pin which is momentary and indicates whenever valid data is received from TX. So i built this simple set up using the logic gates i have. Even though the auto ON of water pump is eliminated, now the output to ULN2803 IC is not stable and the water pump keep on switching ON/OFF and when ON the motor speed is considerably low.
From searching in internet i found that it is due to the instability of VT pin and also when I checked the logic level in VT pin, it keepsRF on changing.
- Can you guys help me with any suggestion or improvement ideas to improve stability of VT pin? or is there any other way of implementing the solution i desire?
Thanks in advance