Looking for the right Latching component

Thread Starter

Jastri

Joined Jul 5, 2016
7
I've been designing a simple random number generator that is supposed to generate a number from 1-100 and display it using three 7-segment displays(D0, D1, D2). This design also uses a 555 timer(astable 1400Hz) and two BCD decade counters. For D0 and D1, I am using CD74HC4511E decoders, which allow me to lock the current inputs by changing *BL and *LE from low to high. This part of the circuit works fine.

For D2, the MSB, I use some logic gates that output a '1' when both BCD counters show '0000'. What I think I need here is a latch of some kind that can lock its value using the same switch from low to high as for the other two decoders. This way they can all lock to their respective values on the same switch.

I realize that I could simply use an additional decoder, but since this 7-seg display will only ever be blank or display a '1', I thought using another decoder would be a waste.
 

eetech00

Joined Jun 8, 2013
1,661
I've been designing a simple random number generator that is supposed to generate a number from 1-100 and display it using three 7-segment displays(D0, D1, D2). This design also uses a 555 timer(astable 1400Hz) and two BCD decade counters. For D0 and D1, I am using CD74HC4511E decoders, which allow me to lock the current inputs by changing *BL and *LE from low to high. This part of the circuit works fine.

For D2, the MSB, I use some logic gates that output a '1' when both BCD counters show '0000'. What I think I need here is a latch of some kind that can lock its value using the same switch from low to high as for the other two decoders. This way they can all lock to their respective values on the same switch.

I realize that I could simply use an additional decoder, but since this 7-seg display will only ever be blank or display a '1', I thought using another decoder would be a waste.
Hi

Post a schematic of your circuit.

eT
 

dl324

Joined Mar 30, 2015
8,958
What I think I need here is a latch of some kind that can lock its value using the same switch from low to high as for the other two decoders. This way they can all lock to their respective values on the same switch.
How many gates are you using to decode 00? It'd probably be simpler to just use another decoder.
 

Thread Starter

Jastri

Joined Jul 5, 2016
7
How many gates are you using to decode 00? It'd probably be simpler to just use another decoder.
I use two 4-input NOR gates and a 2-input AND gate. I'd still need the logic gates even if I use another decoder
 
Last edited:

AnalogKid

Joined Aug 1, 2013
8,109
You might consider using something other than the 4518 for the counter stages. A more full-featured counter chip will have a carry output that can be used to both tie the two stages together without any external gating, and drive the "100" digit. Decoding when to reset the string also will be much easier; a single two-input gate can detect "101" and pull the reset line.

The drawback is that it wil take two counter chips instead of just one, but a lot of other stuff goes away.

ak
 

Thread Starter

Jastri

Joined Jul 5, 2016
7
You might consider using something other than the 4518 for the counter stages. A more full-featured counter chip will have a carry output that can be used to both tie the two stages together without any external gating, and drive the "100" digit. Decoding when to reset the string also will be much easier; a single two-input gate can detect "101" and pull the reset line.

The drawback is that it wil take two counter chips instead of just one, but a lot of other stuff goes away.

ak
While I see how this will work and would probably be much easier, and I certainly will use this design modification if all else fails, but I would still like to know if there is a transparent component that can do what I described
 
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