Help with Binary Counter circuit - Doesn't seem to respond to clock.

Thread Starter

tony1979

Joined May 14, 2017
1
Hi All,
I am new to world of electronics and have embarked on a project of building an 8 bit computer. I am following the videos of Ben Eater on youtube. I have learnt a lot so far and have a good understanding but have hit a road block on my second module 'the binary counter'. I have followed Ben's build video (
) and have reach around 4 minutes in when he gets the counter to start counting. This is where things stopped and I saw no counting on the leds. I purchased the sn74ls161an 4 bit counter and the sn74ls245n bus reciever which are both texas instruments ics. I have checked the datasheets and they match what Ben is using. I have attached a picture of the circuit on my breadboard with some labels of components. The clock I built works well but when I attached the clock to pin 2 of the sn74ls161 nothing happens. I can't see anything I have mispinned and power is going to the circuit (a steady 5v). Ive even tried moved some of the inputs to highs and lows to see if this changes anythings. I only have one sn74ls161 so can not test to see if the ic is the issue. Any help would be most welcome.
Thanks
Tony
 

Sensacell

Joined Jun 19, 2012
2,449
Nothing to do with your problem... but it drives me slightly nuts that there are no current limiting resistors on the LEDs, nor are there any bypass caps on the chip Vcc pins.

This LED setup "hard clamps" the logic output to the LED forward voltage, connecting the same output to another chip might not work- especially if you use a RED LED - because the Vf is lower than a green one.

These omissions might seem trivial, but they are traps set for the unwary beginner, a source of endless frustration trying to figure out why things don't work right down the road.

It's just poor design practice.
 

dl324

Joined Mar 30, 2015
8,918
These omissions might seem trivial, but they are traps set for the unwary beginner, a source of endless frustration trying to figure out why things don't work right down the road.
There's a lot of crap like that on YouTube.
 

dl324

Joined Mar 30, 2015
8,918
Welcome to AAC!
I have attached a picture of the circuit on my breadboard with some labels of components.
No picture...

It's easier for us to help if you post a schematic. Not many of us will trace a breadboard to check connections...
 

Sensacell

Joined Jun 19, 2012
2,449
There's a lot of crap like that on YouTube.
I actually thought it was an excellent tutorial, just missing those details.
It moves through the process of building and testing individual function blocks in a thoughtful and appropriate manner.
 
Top