Operation of 3-minutes Digital Counter

[Wjs]

Hi,

When I simulation this only one display working.

What goes wrong or the gate i used wrong.

Please advise.

 

[mvs sarma]

try with RBO pulled UP

 

[Wjs]

what you mean.

 

[mvs sarma]

please download and see the function table of 74LS247 and the note 3 below the tables. People believe that unused pin is High, but need not always be.

Hence the condition needed sappers to be RBO pin to be pulled UP . You might use 1K resistor for that.

 

[Ian Rogers]

I just sim'd the exact circuit.... It worked fine... The only difference is I didn't use the R/C on the PL line and I used a digital clock input...

 

[mvs sarma]

Fine Ian Rogers,
for some reason the OP did get only 1 digit.
i suggested him to add pull up on 74LS247 "rbo' pin.
the truth table shows like that and He need not leave them open, i suppose.

 

[Wjs]

I tried but still same only one display is counting another two display not counting. are the gate issues ?

 

[mvs sarma]

Can you perform Lamp Test(LT) checking how to do from the datasheet for the respective digits that refused to glow?

possibilities are that displays either faulty or model changed , unless the number tallies. you could sawap the LS247 chips one by one to the working display to check their performance.
Later restore to original locations and try swapping the display devices.
I assuem that you are working on Breadboard.

 

[Wjs]

breadboard it work but in circuit maker it doesn't work

 

[mvs sarma]

i see
once it works on breadboard, forget it
the simulators might have their own deficiencies.
all the best

 

[JoeJester]

When you breadboarded it, did it count past 59 without advancing the minute digit to 1 the first time you fired it up?

If you built it like you drew it, it will.