Hello everyone. this isnt really a homework but I wanted to get more experience with breadboard implementation since it will be useful in my future studies. Recently my class was on the topic of Digit Counters using BCD decade counters.

I was fascinated by it and wanted to visualize the ABCD output of the 74LS192 as 1 and 0 so I made this in proteus.




Seeing as the proteus simulation was working fine and dandy, I wanted to implement the circuit to the breadboard to get more experience building things. I used a 555 1hz timer and replaced the logic probes into LED but when I have everything built on the breadboard, the ABCD (the 2,3,6,7 pins) outputs are always in 1 (the LED are always on) regardless of how the 555 timer pulse.

This is how I connected everything in my breadboard, I used a 5v power supply, a 555 timer and a sn74LS192. I have tripled check the conenctions and they are at the same position as the image below. What did I do wrong in the breadboard implementation? Replies are greatly appreciated!

 

Welcome to AAC!

Seeing as the proteus simulation was working fine and dandy

I don't see how the simulation could be working find and dandy. You don't have the DWN pin tied HIGH, so the counter can't count because Proteus flags the logic level as indeterminant. Even if Proteus treated that as a HIGH, look at the parallel load pin. EDIT: Mistook your upside down power symbol for ground.

What did I do wrong in the breadboard implementation? Replies are greatly appreciated!

Wiring diagrams aren't the same as a well drawn schematic. To make function easier to discern at a glance, we use logic symbols that have inputs on the left and outputs on the right (for the most part), and we label pin function (not everyone will have the pin functions of a 555 timer memorized). And we don't draw wires over text (or components if you're inclined to do that). Pin function should be labeled inside the symbol and pin numbers should be near the I/O's as for the 555 timer.

Your class should have taught you that you can't hang LEDs on the outputs of that counter. If it didn't, you should read the datasheet and enroll at a different school. LSTTL outputs can't sink or source much current and clamping outputs to a couple volts isn't a good idea.

Leaving an input floating "might" give you a logic HIGH, but you shouldn't count on that.

Instead of noting that the LEDs were always on, you should have put that in the text as I find color coded schematics a bore to read. Particularly when the colors are meaningless.

EDIT: A more conventional schematic:

 

There are a number of items to add to your knowledge base from this learning experience as already noted above.

1) Parallel Load input is active low. This is indicated in circuit schematics in two ways (simultaneously), (1) with a bar over LD, and (2) with a bubble on the input.

2) You cannot leave inputs not connected (floating). In 74xx series TTL logic ICs, floating inputs mostly result in a logic high input. Don't take that for granted.

3) You cannot drive LEDs directly from outputs. Use a driver gate instead, for example, 74LS04 Hex Inverters.

4) Do not draw IC pin layouts in circuit schematics. Use a functional logic symbol as per this example:

 

Wasn't TTL used more than 55 years ago?? Google says Outdated.

 

Nobody seems to have mentioned having a 100nF decoupling capacitor between IC2 Vcc and Gnd

 

Nobody seems to have mentioned having a 100nF decoupling capacitor between IC2 Vcc and Gnd

Don't worry. We'll get around to it eventually.