Latch output

[eddieprice19]

I wonder if someone could give me a hand. I am designing a model train controller using the simple 433Mhz radio Tx/Rx discribed on another thread, plus an RF Solutions RF800 encoder/decoder. I have previously used the RF600 encoder/decoder, but this only has 4 inputs and I now want 8. The RF800 has 16. With the RF600 it is possible to have momentary and latched action of the decoder output, but with the RF800 it is only possible to have momentary action, ie the output from the decoder is only ON for as long as the encoder input is ON. I would like to have 4 latched outputs plus 4 momentary outputs. I was hoping to use a D-type flip flop, but it doesn't work, or at least the way I have tried to use it it doesn't. Is there a simple circuit that could give me a latched output?

Eddie Price

 

[alec_t]

According to the datasheet the RF800 can be configured (using pin 5) for momentary or latched outputs:-

Pin 5 (TEN / 204 )
In/Out
Sets outputs to either latched or momentary for operation only with a
204 handheld transmitter.
Logic “1” selects momentary mode
Logic “0” selects latching mode

 

[eddieprice19]

Yes I saw that, but when I spoke to one of the Techs at RF Solutions it only works with the 204 Transmitters as it says, and they cost £54, which is a lot for a model train controller. Anyway I think I have sorted something out after looking through more threads on this forum. The circuit that seems to work is a D-type flip flop with D connected to Q Bar and the momentary signal applied to the clock, latched output taken from Q. At the moment I am using a 4042, quad D-type, but I think I need a 4013, dual D-type - with two separate clock inputs.

Eddie Price

 

[alec_t]

Yes, you will need separate clock inputs.

 

[crutschow]

.....................................
The circuit that seems to work is a D-type flip flop with D connected to Q Bar and the momentary signal applied to the clock, latched output taken from Q. At the moment I am using a 4042, quad D-type, but I think I need a 4013, dual D-type - with two separate clock inputs.

That should work. Just be sure and ground all unused inputs (not outputs) on the 4013 to prevent erratic operation.