LED unexpected sudden BLINK

Thread Starter

amcutp

Joined Dec 25, 2011
4
Here is my friend's project about traffic light.
The 5-bit counter using 74LS163 worked well since we can see the 5 LED indicated.

BUt when deal with 3 types of light (RED: 25s, Yellow: 2s, Green: 5s), the problem comes since the RED light suddenly blink.

I helped him to check the K-map n circuit but still can find the problem.
So, I post it here n would like to ask from your suggestions.

Thank you.
(Refer to the attach file: junction1.ms11 : using Multisim 11)
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,210
You may have mistakenly purchased a blinking-type red LED. Once power is applied to them, they start blinking every 1-2 seconds.

Use a multimeter to test the output voltage, or substitute another LED to see if that is the problem.
 

Thread Starter

amcutp

Joined Dec 25, 2011
4
You may have mistakenly purchased a blinking-type red LED. Once power is applied to them, they start blinking every 1-2 seconds.

Use a multimeter to test the output voltage, or substitute another LED to see if that is the problem.
I tried replacing with most of the available probe in Multisim 11. But, the same problem still comes.
 

SgtWookie

Joined Jul 17, 2007
22,210
Well, of course your red LED is flashing.

You have the left 74LS163 being clocked, and the output goes to the yellow wire, which is ORed into the red LED.

Didn't you expect that?
 

Thread Starter

amcutp

Joined Dec 25, 2011
4
You have the left 74LS163 being clocked, and the output goes to the yellow wire, which is ORed into the red LED.

The 3 RED, YELLOW, GREEN lights on the right hand side are results of logic combination of outputs from 2 IC 74LS163.

Anyway, I think I don't get exactly what you really mean.

My guess is is it the problem comes from using logic gates instead of IC for those AND n OR gates. I'm afraid of the speed problem.
 
Top