4017 cascade problem...?

Thread Starter

noddyspuncture

Joined Jan 15, 2014
22
That is my circuit on post #12, I drew it and tested it.

So you are wanting to light the LEDs sequentially using this schematic. How many LED? Is it being use strictly for LEDs?

Diodes 1- 35 are so you can do patterns, like wig wag lights or police lights. For a straight sequencer they are not needed.

I'll be glad to work with you. Have you built this on a proto-board or what?

Hi Wendy,
I am trying to built a trigger sequencer for some percussion modules. They easily trigger from a slight voltage pulse...!

The sequencer will have three rows of 8 steps and will have the LED's for each stage to show which stage is active. I will then tap the voltage to feed the drum trigger module inputs. I need the ability to make different number of stage sequences... so I will have a rotary switch to tie the first 4017's reset (pin 15) to any of the stage LED outputs to change the count.

I started by building the circuit I attached in my original post... with the 4011 nand gates... and it worked perfectly, but it wasn't sequencing the LED's *steadily* ...maybe OK for flashing LEDs... but is no good for percussion "time keeping". It stuttered... skipping LED's quickly while syaing on others a bit longer. You could easily see it.. so you would definitely hear it...!

So I posted here and it was suggested I replace the 4011 with the diodes and resistors etc as in your circuit...

This I did - in a very rough Xmas tree way, soldering them to each other to test - and it worked very well. Once I decided to tidy it up and transfer the diodes and resistors onto my vero-board, it was still working but with errors like I listed:

If I reset on the 10th step... it cycles 2 > 9.... missing out LED1...!
If I reset on the 6th step.... it cycles to step 5 and then just stops and stays on 5... no matter what.
If I reset on the 4th step.... it cycles to step 3 and it stops and stays on 3 - however, if I put my fingers across LED1 it then cycles 1-2-3 as it should...!

I have only wired the first 10 LED's so far... I thought it might be an idea to sort this problem before progressing and adding more...!?

Well that is basically it... any ideas much appreciated.
Cheers,
Tom
 

Wendy

Joined Mar 24, 2008
22,374
It sounds like your source signal is flawed, the 555 provides the clock signal and should be like a metronome.

It sounds like you either have a wiring error or neglected to put in the bypass caps on the power supply. It could also be the power supply itself is flawed. You must have stable DC on the power supply, and the caps I showed are to prevent the pulses on the circuit from making it to the power supply. It is both a common problem and common solution, a cap next to every chip.

You will not the attachment I included also has a PCB layout.
 

benta

Joined Dec 7, 2015
101
Sheesh...

Why don't you follow the MC14017 datasheet and use MC14081 AND gates?
You started out with 4011 NAND gates, which was clearly wrong, and proceeded to diodes and resistors.
Go back to the original circuit from ON Semiconductor and it will work, provided you have appropriate power supply decoupling.
And by the way, the 555 as oscillator is like putting a steam engine in a modern car. Just sayin'

Benta.
 
Last edited:

Wendy

Joined Mar 24, 2008
22,374
Which does a lot to show your electronic knowledge is lacking.
The 555 works, it is simple. How many of theses circuits have you built?
 

Thread Starter

noddyspuncture

Joined Jan 15, 2014
22
Hi folks,

Many thanks again for all the input and help... and I have an update now.

I decided to go back - strip it down and kind of start again. I removed all the LED's and decided to add the transistor/resistor/LED stage onto the 4017 outputs one-at-a-time. I started with just three - taking the 4th (pin 7) to the reset.

It worked... whereas before the third LED just stopped and stayed lit...!
So I proceeded to add more stages checking each one worked as I went along. I am now sequencing 8 stages successfully...!

I am about to add more - so it will be switching to the next 4017.... so I am anticipating problems... haha!

I'll let you know - but for now it's looking good - again...;)

Cheers,
Tom
 

eetech00

Joined Jun 8, 2013
2,319
As long as your rebuilding the circuit, you should use a ULN2004 chip to drive the LED's.
That way you won't need all those transistors.
 

benta

Joined Dec 7, 2015
101
Which does a lot to show your electronic knowledge is lacking.
Thank You.
Working as an EE in the semiconductor industry since the '80s, this is rich.
At least you could've suggested an ICL7555.

Don't troll me again, please.

Benta.
 

hp1729

Joined Nov 23, 2015
2,304
This is me thinking out loud:
The circuitry around the 555-ic looks odd. Why aren't pin 4 and pin 7 connected to anything? And pin 5 connected to VSS with a 0.01uF cap?
Are the LEDs resistors high enough? (Supply Vs - LED Vf) / I) = (12-3.2)/0.02 = 440R

Now it doesn't say what type of LEDs he has.

How much current can a CD4017 source? 15mA?

I'm sure this doesn't have anything to do with his problem, but still...?
Re: 555
Connecting the resistor to the output gives a 50% duty cycle. The cap is charged and discharged through the same resistor. Discharge pin is not needed. When Threshold is hit the output goes low.
 

Thread Starter

noddyspuncture

Joined Jan 15, 2014
22
Thanks again for the comments... I have now run the circuit up to 10 steps - which means it has switched to the second 4017 - and it runs well...!
I am hoping (and think it will...) continue to perform as I add more stages.

Here's a photo I took today. The 24 piece transistor *forest* is already installed, with the LED's temporarily tagged on for testing. They will eventually end up on a front panel...;)

IMG_5893.JPG
 
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