Troubleshooting a Non-Functional 7 Segment Display Counter on Multisim?

[Dave06]

Hi there

Im building a 7 segment display that counts to 10 when a switch is activated .. this is on Multisim. I've built it to how i think is correct .. unfortunately is doesn't seem to be doing anythin at all ..

Any help is appreciated

 

[vk6kro]

Hi Dave and welcome.

You would need to post a copy of your circuit.

It is common in logic circuits like counters to have a number of pins that have to be grounded or brought to the 5 volt reference level. Have a look for pins like "reset" and "enable" that have to be treated like this and check which way they need to be connected.

 

[Dave06]

Okay thanks here's the circuit

http://tinypic.com/r/2mdf9qq/5

 

[vk6kro]

Can't really see the circuit, but if that is a TTL 7490 or similar, you would need to pull the input to ground rather than to 5 volts when you provide a series of pulses to check the counter.
TTL inputs are already at "high level" and need to be grounded for the counter to change state.

Can you make the circuit a bit bigger?

 

[Dave06]

Ive resised it here now .. thanks

http://tinypic.com/r/n3swpk/5

 

[vk6kro]

You are still pulling the input high with the switch. It is already high so this will not work.

Put a 1K resistor from input to ground and leave the switch where it is.
Or put a 1 K resistor to 5 V from the input and a switch to ground. Simulators like you to be definite about your intentions.

There may be other problems, but the circuit is still unreadable here.

 

[Dave06]

Thanks a lot ... This seemed to fix the problem