20 output running LED

[ferrariako]

Hi! I'am no engineering student so please go easy on me. I just happened to have a subject called "logic circuits".


I can make my own 10 output using 555 timer, and decade counter, but I need a 20-30 output for my project. help me out please!

 

[SABorn]

Most decade counters you can cascade, so you should be able to add several together, to get the 20 or 30 leds you want.

Although you will need to do some blanking after the first count of ten or on eleven the number one led will come on again, then 2 and 12 etc.

 

[ferrariako]

my background on this subject matter is very poor. by cascade you mean???

i need it to function like (555timer-decade counter 10 output) just more outputs.

 

[SABorn]

To start with what is the decade counter you are using?

 

[ferrariako]

4017b err ten characters

 

[SABorn]

The 4017 has a carry out pin that can be fed into the clock input of the second chip (cascade) and so on.

See the pin out attachment.

 

[ferrariako]

thats all? wait ill go try

 

[ferrariako]

not working....

 

[SABorn]

Did you connect the power to the second 4017???

 

[ferrariako]

well yes. the LED's lights up just not the same way as in the first 4017

 

[SABorn]

What do you mean ...not the same way

 

[SABorn]

Is your reset tied low on the second counter and is the enable pin also tied low on the second counter.

 

[Diver300]

When you cascade counters, it is for adding extra digits. One counter counts 0 - 9, two count from 0 to 99, three count from 0 to 999. However, with two counters, there are 20 outputs if you uses 4017s, but there are always two outputs turned on, one representing the tens, the other representing the units.

There is no very easy way of getting two 4017 ICs to count to 0 - 19 and have only one of the 20 outputs come on at a time.

One solution is to connect the LEDs in two banks. Each bank has 10 leds. The positives are connected to one of your 4017 ICs, so two LEDs to each connection.

(LEDs 1 and 11 to output 1, LEDs 2 and 12 to output 2 etc.)

The connect all the negatives of LEDs 1 - 10 together, and all the negatives of LEDs 11 - 20 together. These you connect to outputs 0 and 1 of the second 4017.

Connect the "reset" connection of the second 4017 to its own "2" output. Connect the "clock" input of the second 4017 to the "carry out" connection of the first.

What should happen is that each time the first counter goes from 9 back to 0, there is a pulse on the "carry out" connection. The second counter counts those, so it counts up from 0 to 1. When it gets to 2, the 2 output is connected to the reset, so it goes back to zero. So either the 0 output is high or the 1 output is high.

The LEDs are wired from one of the outputs of the first counter to either the 0 or 1 output of the second counter. The only one that will light is the one connected to the output of the first counter that is high, and is connected to the output of the second counter that is low. The LEDs will not light when reversed.

If you want to go beyond 20 LEDs, you need to invert the outputs of the second counter. There is always only one output of the 4017s that is high. My scheme relies on only one of the outputs that is connected being low. With 20 LEDs, there are only two outputs connected, so only one being low is the same as only one being high, but with more outputs used, they all need to be inverted so that only one is low at any one time.

 

[Shyamal]

Are you need running light? using 555 ic?

 

[audioguru]

Most datasheets for the CD4017 show how to cascade them. You can use logic AND gates or make your own AND gates from diodes and a resistor.

 

[nikkobot]

cant i get the diagram of that 20 output running light using 4017 and 555 IC.

 

[audioguru]

cant i get the diagram of that 20 output running light using 4017 and 555 IC.

I posted the circuit with 25 outputs from the datasheet of the CD4017. Simply take the output to the first CD4017 from Q5 instead of Q9 on the third CD4017.