I have a project traffic light. I build a clock circuit using 555 IC as bellow. I need to count from the given time to 0. for example 120. can anyone help me? i build this circuit using 74190 IC and 7447 BCD to 7-segment. but it doesn't count with the given input(999 - 0).

 

To implement a countdown from 120 to 0, you would load the value 120 (in BCD) into the counter using the PL inputs, and then connect the RST input to a push button or switch. Each time the button is pressed, the counter will count down by one until it reaches 0.

 

As this looks like homework, it has been moved to Homework Help.

 

I have a project traffic light. I build a clock circuit using 555 IC as bellow. I need to count from the given time to 0. for example 120. can anyone help me? I build this circuit using 74190 IC and 7447 BCD to 7-segment. but it doesn't count with the given input(999 - 0) and I need to connect this to 3 LED as green, yellow and red working with timer.

 

As this looks like homework, it has been moved to Homework Help.

sorry, I'm new here thanks for guiding me.

 

The moderators have moved your original post to this sub-forum. No need to repeat yourself again.

 

Is the 555 generating the desired clock signal?
Post a schematic of the exact 555 circuit you are using.

 

Is the 555 generating the desired clock signal?
Post a schematic of the exact 555 circuit you are using.

I'm sure that's working. because blue led is on and of.

 

You are missing the Vcc power connection to Pin 4 and R2.

 

hi @rayan.m

You have created 4 threads for the same topic. STOP creating new threads for the same problem.

Moderation.

 

Your schematic has no supply voltage.
Why are you using very old fashioned TTL 74xx logic ICs?