Class LED project won't run

[Rhoady]

Hi Everyone,

 I am in an introductory electronics class in college and we had to draw a schematic of a simple LED board from a solder practice kit. I had already bought the student version of Multisim, so I thought I would use it to draw the circuit. I would like to simulate the circuit with the software, but do not understand why I can't make it operate like the physical board. I can't even get any of the LED's to light up on the simulation. I think that by the end of the next few semesters I will be able to figure it out, but right now I don't have a clue.

 There were a couple of parts that were slightly different, because the student version didn't have the components.

The assembly instructions called for:

(4) 100 ohm 1/4w Resistor

(1) 1 K ohm 1/4w Resistor

(1) 2.2 K ohm 1/4w Resistor

(1) 10 K ohm 1/4w Resistor

(1) 330 K ohm 1/4w Resistor

(1)100 ohm 1/2w Resistor

(1) 1 uF Capacitor

(1) .01 uF Capacitor

(1) 1N4001 Diode

(1) 1N4735 Zener Diode

(1) PN2222 Transistor

(1) 555 IC

(2) 74LS107 IC

(1) 9 V batery

(2) Green LED

(2) Red LED

 A couple of things that I chose for components that were different were the 100 ohm resistor was suppose to be 1/2w instead of 1/4w, could not see any place to change that. I used a 555_Timer_Rated from the list of 555s. I used a 10 nF Capacitor instead of a .01 uF because it wasn't listed. Also instead of the 74LS107, I used a 74LS107D, which appeared to be a surface mount version from what I could make out from the data sheets I found on them. The one diode that I used was a 1N4001GP and the Zener that I used was a 1N4735A.

 The LEDs are suppose to flash in sequence and turn off in sequence. The physical board I used to draw this with worked fine.

 I don't have to show a working simulation for my class, I just want to know why it won't run. I retraced all of the connections, but I still might have messed up somewhere.

 Any help on this would be greatly appreciated.

Thank you

[JSJD]

I have examined the circuit you submitted; A bit hard to understand since the circuit is draw in a none formal way; All the same I note the following:

GND on IC1 is not connected; run electrical rule check to spot such problems;

CLR lines on IC1 and IC2 are unconnected;

In a practical circuit such pins take on a value of logic 1;

In this case the simulation is taking a value of logic 0, I suspect.

Connect manually to Vcc to put them on logical 1;

IC1 pin 3 (1J) goes correcttly to IC2 pin 11 (2K);

But pin 2 (~1Q) should go to IC2 pin 8 (2J);

But you have taken yours from IC1 pin 7 (~2Q);

Going by the previous stage connections i.e. for

IC2: 2Q --> 1J; ~2Q --> 1K; 1Q --> 2J (IC1); ~1Q --> 2K (IC1); 

For IC1: 2Q --> 1J; ~2Q --> 1K; it follows that 1Q (IC1)--> 2J (IC2); ~1Q (IC1) --> 2K (IC1);

With the above changes the circuits seems to work i.e. flashing LED. I have cleaned up the circuit to remove a lot of lines and connected the GND on IC2 and CLR lines on IC1 and IC2. I have also put in an oscilloscope so that you can observe the waveform on LED4. The circuit is attached. Thanks.

JSJD