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

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Discussion Overview

The discussion revolves around troubleshooting a non-functional 7 segment display counter designed to count to 10 in the Multisim simulation environment. Participants explore potential issues with circuit connections and configurations, particularly focusing on the logic levels required for proper operation.

Discussion Character

  • Technical explanation, Debate/contested, Experimental/applied

Main Points Raised

  • One participant describes their attempt to build a 7 segment display counter and notes it is not functioning as expected.
  • Another participant suggests posting the circuit and highlights the importance of grounding certain pins like "reset" and "enable" in logic circuits.
  • A participant indicates that if the circuit uses a TTL 7490, the input should be pulled to ground rather than to 5 volts for the counter to change state.
  • Further advice is given to use a 1K resistor from the input to ground while keeping the switch in place, or alternatively, to connect a 1K resistor to 5V with a switch to ground.
  • One participant acknowledges that the suggested changes resolved their issue with the circuit.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of proper grounding and input configurations for the counter to function, but there are multiple suggestions on how to achieve this, indicating some level of debate regarding the best approach.

Contextual Notes

The discussion does not clarify the specific circuit details or assumptions about the components used, which may affect the troubleshooting process.

Who May Find This Useful

Individuals working on digital logic circuits, particularly those using simulation software like Multisim, may find this discussion relevant.

Dave06
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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
 
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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.
 
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?
 
Last edited:
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.
 
Thanks a lot ... This seemed to fix the problem
 

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