please help with my crossroad traffic light project...

[D@rkL0rd]

hey guys,i was working on my traffic light project and i created circuit using 555 timer(mono-stable mode) and ic 4017 but when i run the simulation in circuit wizard only first led's light up .i don't know why is this happening please help...

 

[duke37]

I made a traffic light sequencer using a4017. This was to drive full sized lights so used mosfets on the output. I must have the circuit somewhere, it will be on the forum two or three years back.

Your circuit is over complicated. Just feed the 4017 output through a diode to a resistor and base of the switching transistor. More than one output can then be used to light a specific led.

 

[duke37]

I think I have found the circuit. It used one gate of a 4093 - simpler than a 555 - for the timing.

 

[D@rkL0rd]

ya i know that circuit i found it while i was researching for it but according to the question asked for the project i need to use any logic gate and a 555 timer for timing...

 

[KrisBlueNZ]

Hey, that's quite a clever circuit there D@rkL0rd! You're driving two sets of traffic lights and including an amber phase, and you've connected the LEDs in such a way that the red and amber phases for one light drive the green indicator for the other light. Nice!

I can't see any reason why it shouldn't work. You should be aware of possible back-feeding though. Both LEDs and transistor base-emitter junctions have a limit to the amount of reverse voltage they can withstand. For LEDs it's typically around 5V; for transistors, around 7V. If you exceed this voltage, the device will conduct, and can be damaged. You might want to put a diode in series with each emitter.

It would make the design clearer if you positioned the LEDs to correspond to their locations in the traffic light boxes. Also your uploaded image is a bit small and it's hard to make out the components and wires.

Which LEDs did and didn't work when you simulated it?

 

[D@rkL0rd]

Hey, that's quite a clever circuit there D@rkL0rd! You're driving two sets of traffic lights and including an amber phase, and you've connected the LEDs in such a way that the red and amber phases for one light drive the green indicator for the other light. Nice!

I can't see any reason why it shouldn't work. You should be aware of possible back-feeding though. Both LEDs and transistor base-emitter junctions have a limit to the amount of reverse voltage they can withstand. For LEDs it's typically around 5V; for transistors, around 7V. If you exceed this voltage, the device will conduct, and can be damaged. You might want to put a diode in series with each emitter.

It would make the design clearer if you positioned the LEDs to correspond to their locations in the traffic light boxes. Also your uploaded image is a bit small and it's hard to make out the components and wires.

Which LEDs did and didn't work when you simulated it?

Thank you KrisBlueNZ for your time. when i simulated the circuit only the first 2 led's namely r1,r3 and g2,g4 worked. I will upload a bigger image...And for the or gate i used the ic 4072 i couldn't find it the simulator so i had to use these...

 

[KrisBlueNZ]

Thanks for the new diagram, it's better.

I've just noticed a mistake in the green/red connections. the green and red LEDs are swapped. You need the green and amber phases of one light to correspond with the red phase of the other light. Otherwise during each amber phase, one road will have the green light while the other road has the amber light. During the amber phase, you want the other road to have a red light, not a green light! So the red LEDs should be at the bottom of the chain, connected to the 1k resistors.

This doesn't explain why the circuit isn't working in the simulation though.

I don't know why R2 is drawn shorted out.

I don't see any problem with the design. So R1,3 and G2,4 worked. Was the 4017 advancing from one phase to the next? Everything looks right except possibly for pin 7 of the 555 being connected to pin 3. This shouldn't cause a problem but it's not normally done.

 

[D@rkL0rd]

Thanks for the new diagram, it's better.

I've just noticed a mistake in the green/red connections. the green and red LEDs are swapped. You need the green and amber phases of one light to correspond with the red phase of the other light. Otherwise during each amber phase, one road will have the green light while the other road has the amber light. During the amber phase, you want the other road to have a red light, not a green light! So the red LEDs should be at the bottom of the chain, connected to the 1k resistors.

This doesn't explain why the circuit isn't working in the simulation though.

I don't know why R2 is drawn shorted out.

I don't see any problem with the design. So R1,3 and G2,4 worked. Was the 4017 advancing from one phase to the next? Everything looks right except possibly for pin 7 of the 555 being connected to pin 3. This shouldn't cause a problem but it's not normally done.

Sir the red and light led's are connected according to the given logic table i have uploaded...i cant understand how r2 is shorted out...sir that is what i think is the problem here it is not going to the next phase...sir what do i do of the pin 7 sir please tell me ...thanx

 

[KrisBlueNZ]

You don't need to connect pin 7 of the 555 to anything.

Is the 555 oscillating? Does pin 3 change state periodically? If not, there's something wrong with the 555 oscillator. If it does, there's something wrong with the 4017. I can't see any errors in your diagram.

Re R2 I was asking why you have drawn it with a wire connecting through it, shorting it out. With R2 shorted out, the LEDs will draw a lot of current and could be damaged (if it was a real world circuit).

 

[D@rkL0rd]

You don't need to connect pin 7 of the 555 to anything.

Is the 555 oscillating? Does pin 3 change state periodically? If not, there's something wrong with the 555 oscillator. If it does, there's something wrong with the 4017. I can't see any errors in your diagram.

Re R2 I was asking why you have drawn it with a wire connecting through it, shorting it out. With R2 shorted out, the LEDs will draw a lot of current and could be damaged (if it was a real world circuit).

sir , i have decided to start all over again and doing it in small sub-circuits. starting with the 555 timer producing 1 pulse every 1 sec can you pls tell me a circuit to do so...i tried but there seems some problem please tell me...thnx

 

[KrisBlueNZ]

The standard oscillator circuit using a 555 is shown in the data sheet, and in about a zillion places on the web: https://www.google.com/search?q=555+oscillator&tbm=isch

Values of 100k, 100k and 10 µF are suitable for a starting point.

 

[D@rkL0rd]

The standard oscillator circuit using a 555 is shown in the data sheet, and in about a zillion places on the web: https://www.google.com/search?q=555 oscillator&tbm=isch

Values of 100k, 100k and 10 µF are suitable for a starting point.

Thnx... i tried one but it does not seem like constant for 1 sec...please tell me what am i doing wrong here...

 

[duke37]

The output p3 is connected to p7 discharge. I think the powerfull output circuit will win the contest.

I think that leaving p6 and p7 open and connecting the timing resistor between output and trigger, p2 will do the job, making a similar circuit to my 4093 circuit. I don't think you need C2 in this case.

 

[KrisBlueNZ]

You haven't copied the 555 oscillator circuit properly.

Pin 3 does not connect back to the timing components.

The top resistor connects to VCC, not to pin 7.

Pin 7 connects to the join between the two resistors.

Pins 6 and 2 connect to the join between the bottom resistor and the capacitor.

Don't worry about the timing not being exact. Just get it oscillating to start with.

 

[D@rkL0rd]

You haven't copied the 555 oscillator circuit properly.

Pin 3 does not connect back to the timing components.

The top resistor connects to VCC, not to pin 7.

Pin 7 connects to the join between the two resistors.

Pins 6 and 2 connect to the join between the bottom resistor and the capacitor.

Don't worry about the timing not being exact. Just get it oscillating to start with.

i did what you said but its not oscillating anymore...its just on

 

[D@rkL0rd]

The output p3 is connected to p7 discharge. I think the powerfull output circuit will win the contest.

I think that leaving p6 and p7 open and connecting the timing resistor between output and trigger, p2 will do the job, making a similar circuit to my 4093 circuit. I don't think you need C2 in this case.

Noop it does not help it only makes led less bright and stopes oscillating...

 

[KrisBlueNZ]

Now you've got pin 2 connected to 0V. It needs to connect to the same point as pin 6.

You've also shorted the power supply out.

 

[D@rkL0rd]

Now you've got pin 2 connected to 0V. It needs to connect to the same point as pin 6.

You've also shorted the power supply out.

i dont understand what do you mean by shorted the power supply...
i did connect the pin 2 to pin 6...

 

[Harald Kapp]

The short is marked red in this picture:

i did connect the pin 2 to pin 6...

you did now, but not in the picture from your previous post #15.

 

[D@rkL0rd]

thank u very much evryone it is now oscillating for 1 sec ...first part of the project completed...now to the second part the counter...