Help with LED sequencer

[RyanKunk]

Help troubleshooting LED sequencer?

Im pretty new to all this but ive worked this up. evertime i press the button it goes to the next LED. I will be using this as the basis for a cable tester. the only problem is that there is a pause between LED 8 and LED 9, the switchover between 4017's. another small thing when the simulation starts up it lights up a few random LED's untill i depress the button. could just be a simulation error.

 

[duffy]

Pin Q5-9 is an output, you have it shorted to Vss. Leave it open.

And add a .1uf decoupling cap across the power supply near the counters.

 

[ericgibbs]

Im pretty new to all this but ive worked this up. evertime i press the button it goes to the next LED. I will be using this as the basis for a cable tester. the only problem is that there is a pause between LED 8 and LED 9, the switchover between 4017's. another small thing when the simulation starts up it lights up a few random LED's untill i depress the button. could just be a simulation error.

hi,
Q5-9 on the 1st 4017 is the output to clock the next 4017.

Also use a gate for the RESET line together with the Q5-9 going low on the 2nd 4017 OR this with a 47K and 100nF cap [across the supply rails] as a power on RESET.

Do you follow OK.?

 

[duffy]

He has the clock connected correctly for the round-robin counter. Here, check the spec sheet:
https://www.electro-tech-online.com/custompdfs/2009/01/cd4017b.pdf

A power-on reset would help. Get rid of that shorted output first and see how it behaves.

 

[audioguru]

Why do you have a lousy old 7400 IC in there? It needs a regulated 5V supply that you don't have and its input current is too high for the CD4017 to drive. Use a Cmos IC instead, the CD4011.

 

[duffy]

Hey! Good find.

 

[RyanKunk]

Why do you have a lousy old 7400 IC in there? It needs a regulated 5V supply that you don't have and its input current is too high for the CD4017 to drive. Use a Cmos IC instead, the CD4011.

I i added a voltage regulator in there, i have the physical part but i forgot to add it in the simulation.

i replaced the 7400 since it was ghetto.

ive been trying to read up on PoR's but im not sure what exactly it consists of and how to implement it. most of the stuff i saw didnt explain it very well for a beginner.

there is still a pause between 4017's

ive attached the updated schematic.

thanks so much for the help guys. sorry if im slow this is my first project.

 

[RyanKunk]

hi,
Q5-9 on the 1st 4017 is the output to clock the next 4017.

Also use a gate for the RESET line together with the Q5-9 going low on the 2nd 4017 OR this with a 47K and 100nF cap [across the supply rails] as a power on RESET.

Do you follow OK.?

i was a little confused by the Q5-9 port i didnt see it on the data sheet for my component what is it designed for?

 

[duffy]

It's an overflow output for when it goes past 9.

 

[audioguru]

Why is there a 5V regulator? It is needed for the lousy old 7400 gate but is not needed and is not wanted with the Cmos iCs. The LEDs will be dim with a 5V supply and will be much brighter with a 9V supply.

The circuit misses the first output of the second CD4017 which causes a pause.
Why don't you make the cascaded circuit in the datasheet?

 

[RyanKunk]

It's an overflow output for when it goes past 9.

Oh it's just the 'carry' the different nomenclature threw me off

 

[duffy]

His cascade looks the same as the one in the TI data sheet to me - what am I missing?

Yes, if you replaced the 7400 with the 4011, go back to the 9V supply or cut those led resistors in half.

 

[RyanKunk]

Why is there a 5V regulator? It is needed for the lousy old 7400 gate but is not needed and is not wanted with the Cmos iCs. The LEDs will be dim with a 5V supply and will be much brighter with a 9V supply.

The circuit misses the first output of the second CD4017 which causes a pause.
Why don't you make the cascaded circuit in the datasheet?

I'll get that regulator out of there.

I'm building a cable tester so I need it to be a maxium of 16 pins. This is the pin selector.

 

[audioguru]

His cascade looks the same as the one in the TI data sheet to me - what am I missing?

The circuits are completely different. He uses a NAND gate but the datasheet uses an AND gate.

I modified the circuit in the datasheet for 16 outputs without a pause. But the circuit is missing a power-up-reset like the circuit on the web by Bill Bowden. I "stole" his Mickey Mouse discrete AND gate.

 

[duffy]

Shoot, missed that one, too. Must be going blind. Thanks.

Damn, Ryan - it's a wonder this thing doesn't just explode or something.

 

[RyanKunk]

The circuits are completely different. He uses a NAND gate but the datasheet uses an AND gate.

I modified the circuit in the datasheet for 16 outputs without a pause. But the circuit is missing a power-up-reset like the circuit on the web by Bill Bowden. I "stole" his Mickey Mouse discrete AND gate.

so i might be a total tool? ...its possible
but here are the two other things i tried. the resistor diode combo (which about every other time seemed to blow the timer) and the AND gate that is in there now. both seem to skip a beat still.

barring that my IQ has dropped 60-70 points in the last week or so it seems to me that it should be working now. no?

 

[RyanKunk]

according to my interpretation of the data sheet Q0 on the first 4017 should be acting as an led output as well but in previous attempts it doesnt seem to do that

 

[ericgibbs]

hi Ryan,
Dont worry about your IQ.

If I understand correctly you want the first 4017 to count upto 9 [thats 0 >9]

When it clocks off the 9, it clocks the second 4017 on one count from 0 > 1
and so on.

So it goes [4017A] 0 > 9 > 0 and the [4017B] 0 > 1
then it goes [4017A] 0 > 9 > 0 and the [4017B] 1 > 2 ....

So 4017A counts units and 4017B counts in tens.???

 

[ericgibbs]

according to my interpretation of the data sheet Q0 on the first 4017 should be acting as an led output as well but in previous attempts it doesnt seem to do that

When the 4017 is RESET Q0 is high.

EDIT:
Are you trying to configure a 1 of 'n' cascaded counter.???


EDIT2:

Look at this image.

 

[audioguru]

Bill Bowden's Cascaded CD4017s

I copied a mistake on the datasheet for my second counter. Maybe the circuit on the datasheet has another error.

Bill Bowden's circuit probably works. Make it count to 18 then reduce it to count to 16.