# TinkerCAD 7-Segment Display Not Showing on Simulation

#### Swaysceptile

Joined Oct 28, 2021
16
Hi, I am only on my 5th week trying out TinkerCAD for our Logic Circuits course. We are tasked to create a 7-Segment Display Using Logic Gates only. I did all the boolean expressions needed for each segment using K-MAP, and identified the boolean expression needed to create my circuit.

I am doing the segment A circuit and wiring currently but the 7-Segment didn't output anything after simulating. It should have light on Segment A.

How could I solve this? Thanks for those who will help. Please let me know if there is a problem with the link or you need to know more.

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#### dl324

Joined Mar 30, 2015
14,467

#### Swaysceptile

Joined Oct 28, 2021
16
Hi, I already fixed this problem. I just wanna inquire about another problem that I encountered. The same circuit that I mentioned on my post, but, if I try and simulate it, the 7-segment display is not showing. I'm not sure where the exact problem is because I did all the connections based on my equation. I just can't see where I got it wrong for the output not to work. This one is still for Segment A circuitry. The output should be that the segment A already has light on the 7-Segment.

BTW, sorry for the mess, I am still working on how to wire properly.

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#### dl324

Joined Mar 30, 2015
14,467
I just wanna inquire about another problem that I encountered.
Do you have a schematic? I don't trace breadboards unless I suspect that the person in question doesn't know how to wire properly.

You shouldn't run wires over/under components or along the pins because we can't trace/determine connectivity.

If you're not required to use that simulator, I'd use something that simulated from a schematic:

This is from a binary to hex converter I did in DigitalWorks (a free simulator that runs on Windows). It does have some standard components, but I don't use them because schematics using them are difficult to read.

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#### Swaysceptile

Joined Oct 28, 2021
16
Do you have a schematic? I don't trace breadboards unless I suspect that the person in question doesn't know how to wire properly.

You shouldn't run wires over/under components or along the pins because we can't trace/determine connectivity.
View attachment 265601
Hi, sorry but I directly used the equation itself and made the wirings on breadboard and didn't do a schematic anymore. I'm hoping you could take a look at the link itself if it's okay, and see the problem. I'll try to fix the wires later. I just want someone to take a look and see where might the problem be (if it's okay). Thanks.

#### dl324

Joined Mar 30, 2015
14,467
I just want someone to take a look and see where might the problem be (if it's okay).
I'm not going to trace something that messy.

#### ci139

Joined Jul 11, 2016
1,821
There seems to be no limiting resistor from "driver-"/logic- ic to the 7-seg. LCD indicator

#### Swaysceptile

Joined Oct 28, 2021
16
Hi, I am only on my 5th week trying out TinkerCAD for our Logic Circuits course. We are tasked to create a 7-Segment Display Using Logic Gates only. I did all the boolean expressions needed for each segment using K-MAP, and identified the boolean expression needed to create my circuit.

I am doing the segment A circuit and wiring currently but the 7-Segment didn't output anything after simulating. It should have light on Segment A.

How could I solve this? Thanks for those who will help. Please let me know if there is a problem with the link or you need to know more.
There seems to be no limiting resistor from "driver-"/logic- ic to the 7-seg. LCD indicator
I tried adding a 1k Resistor from the output to the A pin of the 7-segment but it doesn't seem to work. Would you mind taking a quick look to see where the problem might be?

#### dl324

Joined Mar 30, 2015
14,467
Would you mind taking a quick look to see where the problem might be?

It's unclear what the pinout is for the seven segment display, but you have the orange wire connected to an input (A4) on the HC32.

From an onsemi datasheet:

#### ci139

Joined Jul 11, 2016
1,821
GFRAB // 7seg pinnout can be swapped in between Com-AN / Com-CA
EDRCG // i a bit cleaned up the ckt - but i didn't checked it's functionality yet . . .

#### Swaysceptile

Joined Oct 28, 2021
16
GFRAB // 7seg pinnout can be swapped in between Com-AN / Com-CA
EDRCG // i a bit cleaned up the ckt - but i didn't checked it's functionality yet . . .
View attachment 265619
Did the 7-segment display finally lit up? Please check because it would really help, thanks!

#### ci139

Joined Jul 11, 2016
1,821
i changed it to a common cathode as you had the Comm connected to neg supply rail - it did lit up the segment A but it didn't respond to any alteration of the toggle button states ??? sorry . . . though i didn't run through all the 16 combinations . . . = i might've missed something

? are you trying to build the 4-bit to 7-seg hex coder < such will be quite complex . . . should put the schematic diagram on paper before attempting to tile it up on pin-boards
random about https://www.dcity.org/portfolio/i2c-7-segment-led-library/ + a ROM version of the thingy https://www.futurlec.com/Datasheet/Motorola/MC14495.pdf

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#### Swaysceptile

Joined Oct 28, 2021
16
i changed it to a common cathode as you had the Comm connected to neg supply rail - it did lit up the segment A but it didn't respond to any alteration of the toggle button states ??? sorry . . . though i didn't run through all the 16 combinations . . . = i might've missed something

? are you trying to build the 4-bit to 7-seg hex coder < such will be quite complex . . . should put the schematic diagram on paper before attempting to tile it up on pin-boards
random about https://www.dcity.org/portfolio/i2c-7-segment-led-library/ + a ROM version of the thingy https://www.futurlec.com/Datasheet/Motorola/MC14495.pdf
Actually I'm only trying to make a 7-segment display using only logic ics and not with the actual decoder

#### ericgibbs

Joined Jan 29, 2010
15,526
Actually I'm only trying to make a 7-segment display using only logic ics and not with the actual decoder
Hi Sway,
That is not an easy task, this image of a decoder shows the complexity of the logic using Gates.
It could be simplified a little by dropping Blanking and Lamp testing section.
Post your version of the decoder.

E

#### ci139

Joined Jul 11, 2016
1,821
One way to control each segment separately is to use a bit-mask
--e.g.-- the 7 switches (1 for each) or a register/buffer of 7-bits . . .

for encoder or decoder - depending how you call it :

a0:aF = 10110 11111 101011 goes for
DCBA
0000
...
0111
1000
...
1111
as
$$\begin{array}{|c|c|c|c|c|c|}\hline {} & B & B & \overline{B} & \overline{B} & {}\\ \hline D & 1 & 1 & 0 & 1 & C\\ \hline D & 0 & 1 & 1 & 1 & \overline{C}\\ \hline \overline{D} & 1 & 1 & 1 & 0 & C\\ \hline \overline{D} & 1 & 1 & 0 & 1 & \overline{C}\\ \hline {} & A & \overline{A} & A & \overline{A} & {}\\ \hline\end{array}$$
$$a=\overline{A}\left({B+\overline{C}+D}\right)+B\left({C+\overline{D}}\right)+AC\overline{D}+\overline{B}\ \overline{C}D$$
and obviously also
$$a=\overline{A\overline{B}\left({CD+\overline{C}\ \overline{D}}\right)+AD\left({B\oplus C}\right)+\overline{B}\ \overline{D}\left({A\oplus C}\right)}$$
the seg. a(0...F) may be optimized for the logical gates you'll use to implement it

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