HT12D Latching Trouble

[conquersthing]

HI,

i have read all the threads and can not find or understand and answer to the problem im currently having.

i want to use the output pins of the HT-12D to drive relays but only on a momantary basis. not latched like the Chip puts out.

a google search came up with someone having the same problem and someone suggested 1.The HT12D is a latch type decoder,if you want a momentary function,you can 'AND' the VT pin with D8~D11. I dont understand how this would work (basic knowlodge but learning quickly). if someone could explain in to me that would be muchly appreciated.

Cheers

 

[eblc1388]

a google search came up with someone having the same problem and someone suggested 1.The HT12D is a latch type decoder,if you want a momentary function,you can 'AND' the VT pin with D8~D11. I dont understand how this would work (basic knowlodge but learning quickly).

The VT signal only goes HIGH when the input signal is keep transmitting. Using the voltage of this pin, you can control the outputs when and only there is transmission.

An 2-input AND gate output goes HIGH only when both of its input pin is HIGH.

Using a Quad-2 AND Gates, which has 4 AND gates each with two input pins, you connects together one input of all AND gates together to the HT-12D VT pin, each of the remain AND gate pins goes to HT-12D respective latched data output. You then get the output from the AND gates output instead of the HT-12D output.

Note: If you transmits briefly but wants the output to hold for a time longer than the transmission, a different circuit design is needed.