7-seg display never works for me

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Discussion Overview

The discussion revolves around troubleshooting issues with a 7-segment display, focusing on the use of a 7447N integrated circuit for BCD to 7-segment conversion. Participants explore various configurations, inputs, and the application of current limiting resistors, while also seeking theoretical explanations for their observations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant expresses frustration with a 7-segment display that shows all segments lit, despite having the correct outputs and experimenting with common anode and cathode configurations.
  • Another participant requests a description of the integrated circuit (IC) used, noting that the AND/OR combinations appear unusual.
  • A participant clarifies that the display is for the "units" digit of a three-digit number, indicating that the 5th output is intentionally left unused.
  • Questions are raised regarding the ~EL input and whether the participant is using a display with active low inputs, as well as the necessity of the gates in the circuit.
  • One participant corrects themselves, revealing that the submitted screenshot was of a 4511 IC and explains the function of the EL input as an enable latch, which should be high.
  • Another participant confirms that the EL input should indeed be high, but notes that since it is inverted, it should still function correctly.
  • The original poster concludes that the issue has been resolved.

Areas of Agreement / Disagreement

The discussion includes multiple viewpoints regarding the configuration and functioning of the 7-segment display and the associated IC. While some participants provide clarifications and corrections, there is no clear consensus on the initial troubleshooting steps or the theoretical underpinnings of the issues faced.

Contextual Notes

Participants mention current limiting resistors and their application, but there is a lack of detailed theoretical discussion regarding their necessity and function in the circuit. Additionally, the specifics of the binary to BCD conversion process and the role of the gates remain somewhat ambiguous.

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7-seg display never works for me:(

Im flippin out. I always have this same problem with 7-segment-displays having only touched on theory stuff I don't know why this 7-seg display won't work. I've attached up probes and it shows all the right outputs.

ive fiddled with common anode and cathode displays, I have used 7447N for the conversion.

ive tried all combinations of EL EN BI and all I can get is it shows all segments lit up.

most of the time I see current limiting resistors but I am not sure how to apply them. there in nearly every example but nowhere is the theory for it.

ive attached the multisim 11 file

any help would be great. thanks.

and if possible the theory behind any of it.
 

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If you have some description of your IC, it would help if you could share it.

Those AND/OR combinations look strange to me.
 
It's bin-BCD Conv
It's the "units" digit of what will be 3 digits. That's why the 5th output is left untouched.
 
What is the description of the ~EL input? The 7447 outputs are active low. Are you using a 7-segment display with active low inputs? Finally, what is with all the gates? Why don't you feed the switch outputs directly into the D inputs? Or is there more you haven't told us?
 
Oh never mind. The screenshot I submitted is actually a 4511. And EL is enable latch. And it should be high.

And the gates convert the binary inputs into the switch to BCD for the display. So I know binary and BCD are equal for 0-9 but now when binary 10-11-12-14-15 is on the switch it just displays the "units" digit.
 
Actually it's right. EL should be high, but since its inverted it should be low. So it should still work.
 
All fixed (:
 

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