Joining 2 digital signals

[ForceMaster]

Hi,
sorry for bad english,

Is it possible to do the following,
join 2 output from ex 7490, to one input,
with a diode like on the drawing ?
not neassesary to be 7490, could also be GATES (OR NOR, NAND AND ) or.

Rgds
ForceMaster.

 

[Resqueline]

Yes you can, but only if you provide a pull-down resistor at the 7447 input. The use of diodes in this manner will create an OR gate however. Is that what you want?

 

[ForceMaster]

Yes you can, but only if you provide a pull-down resistor at the 7447 input. The use of diodes in this manner will create an OR gate however. Is that what you want?

Hi
thanx, how to do the pull down resistor , og how " big" ?

Rgds
ForceMaster

 

[Resqueline]

I'll have to withdraw my previous statement.. It's valid for CMOS circuits but it won't work for TTL circuits. You'll have to use AND or OR gates as suitable to "join" TTL outputs.

For CMOS circuits the pull-down resistance value is a compromise between speed and noise immunity, with drive voltage as a further complication, but 10kΩ should be ok.

 

[ForceMaster]

I'll have to withdraw my previous statement.. It's valid for CMOS circuits but it won't work for TTL circuits. You'll have to use AND or OR gates as suitable to "join" TTL outputs.

For CMOS circuits the pull-down resistance value is a compromise between speed and noise immunity, with drive voltage as a further complication, but 10kΩ should be ok.

Hi,
Can this work,
When i push one of the buttuns, the 7447 will show the info from the first counter.
and when buttom 2 it will show the info form the next counter.

Will it work ??

I know it's not finish, cause i can select more than one, of a time, but dont worry abouth that.
Rgds
ForceMaster

 

[Resqueline]

No, that won't work, because like I was trying to say in my previous post the IC's are TTL. If they had been CMOS (4000 or 74HC series) it could have worked.
What you're trying to do there is not joining outputs, but selecting them.
What you need is called a data selector, or a Multiplexer.
If you replace the diodes with a 4-input OR-gate it may work.
Or you can replace all the AND-gates & diodes with a 74153 (4-input multiplexer).

 

[ForceMaster]

okay, so if i use 4518 ( or one like that) as counters
4081 as AND Gate.
Diode as shown, and 4511 as 7-seg driver then it will work, if i put a 10 k, resistor to pull up.

Will it work then ????

rgds
ForceMaster

 

[ForceMaster]

Hi again.

I will try to explain a little better,
it will be used so when i select counter 1, all other counters output is block by the AND Gate, so it's not "joining 2 digital signals" byt more selecting,
i know i can fix it by using OR gates, but if i have 10 different counters, it will be a lot of OR. 10 different counters with 4 digits, it gives many many OR.
if it can be fixed by the diodes, it will be much easyer and cheaper.

Rgds
ForceMaster

 

[Resqueline]

Yes, that sounds like it would work, except you use a pull-down resistor.
Diodes are used like that in commercial equipment just for the reasons you mention.

 

[ForceMaster]

Hi Again

Need some more help.
Have counters(8 pcs.) and when the day shift, i will have to move all data from counter 1 to counter 2 ( or a storage of some kind ) and when i have 7-8 days, it should just disapear.
if you know what i mean,

The outputs from "Storage" or counter 2-8 i will loop thru a AND gate and up to 7 seg output, but that's easy.

Rgds
ForceMaster

 

[ForceMaster]

Yes, that sounds like it would work, except you use a pull-down resistor.
Diodes are used like that in commercial equipment just for the reasons you mention.

Sorry Pull down, ,,,
'Exect from that, then it will work ?

Have tried to figure out the other problem, and will it work,
when day shifting, the data shift from one 7475 to the next,
i think it will work, but what do you mean, ?
I know it's not fancy, but simpel..

Rgds
ForceMaster