# Help with a simple project!

1. Nov 25, 2004

### Electro

Hello,
I am finishing my first semester as an electrical engineer. Thus, we have to do a final project. The problem is that I didn't have to much time in the lab to finish it up, so it is a little bit difficult to solve it theoretically. If anyone can help, I would be grateful.

The project is to design a simple traffic light controller using a power supply, a 555 timer, a 74163 counter, 6 LEDs , 6 330 Ohm resitors, 2 capacitors and logic gates (Later some other resistors and capacitors should be used in order to specify an exactly 1 sec. time for each count)

I went up OK with the 555 timer and counter. I connected them and the LED s too. The problem is with the logic. The LEDs do not obey the law of the traffic light. In other words there is a problem which I can't solve if I don't have the circuit in front of me. I used an AND gate, a NOT gate and I plan to use an OR one. Can you please help me to define a logic for the circuit? I tried several times but with no success. I have attached the truth table for the whole 16 sec. cycle. This is the main concern; after that I can figure out what capacitor and resistor to use so that I will have exactly 1 sec. counts.
Thank You

#### Attached Files:

• ###### TruthTab.zip
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Last edited: Nov 25, 2004
2. Dec 4, 2004

### wire2

This is similar to a project I did years ago while learning to program PLC's. Ours included sensing for advanced left turn lanes.

I see your post is a few days old so I may be too late but here goes a try;

Let's call the north-south lights (M)ain street and east-west (S)ide street, along with r, y and g.
Take counter bit 1 directly to Sr, and through an invertor (both inputs of a NAND) to Mr, to give 8 seconds red alternately.
For My, take bit 1 after the same NAND, then AND it with bit 2, then AND the output with the output of ANDed 3 & 4. That will be true in step 7.
For Sy invert bit 4, then AND it with bit 3, then AND that output with the output of ANDed bit 1 & 2. (True in step 15)
Green will be on when you NOR a y and r on the corresponding street, you should be able to work that part out from here.

Last edited: Dec 4, 2004