Hello, we are having a 4 way traffic lights using 555 ic timer only, not arduino or any microcontroller.The problem is, how can i preset value (55s) in a 74ls192 ic, and after it goes 00, it would preset to 30 seconds after it goes 00 again it would go back to 55s, and is 74ls47 best decoder paired with 74ls192?

 

Quite a bit of detail is left out of the request, what I think I see is a digital count-down traffic light, with LED displays , and different times for the different directions. One question is why the 192 and not the 190? The different presets can be provided by an arrangement of diode "OR" inputs. What is the purpose of two different times?
The 74LS47looks like a reasonable choice for driving an LED display, although certainly driver transistors will be required.

 

Quite a bit of detail is left out of the request, what I think I see is a digital count-down traffic light, with LED displays , and different times for the different directions. One question is why the 192 and not the 190? The different presets can be provided by an arrangement of diode "OR" inputs. What is the purpose of two different times?
The 74LS47looks like a reasonable choice for driving an LED display, although certainly driver transistors will be required.

Yes it is a digital countdown traffic lights, do you have any schematic diagram for your own design?

 

Quite a bit of detail is left out of the request, what I think I see is a digital count-down traffic light, with LED displays , and different times for the different directions. One question is why the 192 and not the 190? The different presets can be provided by an arrangement of diode "OR" inputs. What is the purpose of two different times?
The 74LS47looks like a reasonable choice for driving an LED display, although certainly driver transistors will be required.

The 55 seconds is for red and the 30 is for green light

 

Is this homework?

 

Is this homework?

Nope, our project in school

 

It may be simpler to just use two counters. If you use CMOS counters and drivers it will consume much less energy, and save money on power as well. AND you can run it at a higher voltage,which improves efficiency and noise immunity.

 

I have presetted it at 55 seconds but when it goes 00 it goes back to 55 seconds, how can i make it count to 30 seconds then goes back to the first preset

 

If there is a microcontroller involved, you can use that as the counter!

 

If there is a microcontroller involved, you can use that as the counter!

We are not allowed to use microtonroller or arduino

 

OK, the solution is to not have the preset hard wired, but rather provided by a logic controlled diode "OR" arrangement, like I mentioned in post #2. The other simple option would be to have a separate timer for each color of light, red, yellow, and green. That scheme will make future adjustments of the times much simpler. Even DIP switch programmable.

 

If the problem is to make “a 4 way traffic lights using 555 ic timer only”. And you use a 74LS92, then you have’nt solved the problem, have you?

 

I am thinking that a traffic light using ONLY 555 devices would probably lead to a lot of very exciting issues in a short amount of time.

 

I misread your earlier post. You can do it with only NE555’s - a lot of th. Can you use a counter with a load input such as the 74163, etc?

https://www.ti.com/lit/ds/symlink/sn74f163a.pdf?ts=1736843873084&ref_url=https%3A%2F%2Fwww.google.com%2F

 

In a real engineering environment a rational request would not make such a demand, like using only 555 timer IC devices.
BUT to do it that way will take at least two 555s to generate the two delays, and then two more to generate the very short delay between colors. So at that point there are four analog timers that need to operate 24/7/365, for at least ten years, and never drift with temperature. AND they need to operate some rather demanding SSR devices to control the actual lights, UNLESS this is a traffic light for a model train setup. That is a much less demanding application.
But since the TS is a student I am guessing that it is an assignment.

 

I used 74ls190 and 74ls47. I put a nand gate for zero detection and connected it to the load pin. I have achieved the 55 seconds but how can i start it to a new preset if it goes 00. ( 55-00-30-55 ) the sequence i want to have, a help would be appreciated, this is our finals exam.

 

Is it possible to achieve that with a d flipflop?

 

I already described exactly how to do it by providing two different preset input combinations. Was my description really that difficult to visualize??

 

I already described exactly how to do it by providing two different preset input combinations. Was my description really that difficult to visualize??

Really sorry i really can't visualize it. This is our first time doing practical projects... Can you please elaborate to me where does the logic OR arrangement goes? The input of the logic diode are from the output BCD of the 74ls190? Then both are connected to an OR Gate? Then the output where will go? Sorry for my stupidity, i cant really understand how can i load the two presets, huhuhu

 

The simple scheme would use diodes in a scheme similar to a ROM, connected to each preset input. The other end of the diodes would be the select line to feed the 5 volts to the diodes connected to the preset inputs. So to select 33 seconds, the diodes will feed the "1", "2", "10", and"20"inputs on the counter. All of the preset inputs will also have pull-down resistors to common. so that all the non-selected inputs are zeros. For the 55 second setting, the inputs would be 1,4,10, and50.
and the bias would be applied to the other end of those diodes.
Does that explanation make sense? It is the diodes that are serving as the OR gates.