cd4017

[littletransistor]

hey there,

I'm trying to construct a running lights system, and hooked the 555 astable into the input (CLK) of CD4017, and let the rest do the job by connecting it according to the requirements in the datasheet.

However, I bumped into a problem... first - I'm making a 6-LED one, so I connected the 7th output into the Reset. Then, only a few LED are running, where outputs 0, 1, 2 and 6 are there. The 3, 4, 5 refused to lit up no matter how much I have reconnected it.

What could be the problem, the breadboard or the CD4017 chip?

 

[ericgibbs]

hey there,

I'm trying to construct a running lights system, and hooked the 555 astable into the input (CLK) of CD4017, and let the rest do the job by connecting it according to the requirements in the datasheet.

However, I bumped into a problem... first - I'm making a 6-LED one, so I connected the 7th output into the Reset. Then, only a few LED are running, where outputs 0, 1, 2 and 6 are there. The 3, 4, 5 refused to lit up no matter how much I have reconnected it.

What could be the problem, the breadboard or the CD4017 chip?

hi,
Its not easy to determine whats wrong from your description.
Couple of questions.
Do you have a resistor in series with your LED's
Whats the forward voltage drop on the LED's [ are they the same type?]
Whats the 4017 supply voltage.
How have you connected the other pins on the 4017?
How are you clocking the 4017?

Do you have a drawing to post?

 

[littletransistor]

Okay, here's the circuit...

But what's the capacitor's doing in around the CD 4017?

 

[audioguru]

Every battery powered circuit needs a supply bypass capacitor to keep the supply from jumping around when things like a 555 conducts a brief supply current of about 400mA when its output switches.
Without a supply bypass capacitor then the CD4017 will probably lose its supply voltage for a moment then its outputs will be random.

 

[Gordz]

The counter is succeptable to supply noise, decouple your 555 well !

 

[audioguru]

Use a Cmos 555 (LMC555, TLC555 or ICL7555) to drive the Cmos CD4017. Its supply current spike is much less than an ordinary 555.

 

[littletransistor]

Use a Cmos 555 (LMC555, TLC555 or ICL7555) to drive the Cmos CD4017. Its supply current spike is much less than an ordinary 555.

I currently have the NE555. So how am I gonna cut down on the current spike? Am I going to couple the pin 5 of my 555 to the ground with a small cap?

 

[audioguru]

I currently have the NE555. So how am I gonna cut down on the current spike? Am I going to couple the pin 5 of my 555 to the ground with a small cap?

A capacitor is used to filter the pin 5 voltage of a 555 when your power supply voltage has mains hum.

National Semi says, "Adequate power supply bypassing is necessary to protect associated circuitry. Minimum recommended is 0.1uF in parallel with 1uF electrolytic."
The 0.1uF ceramic disc is a good bypass capacitor at high frequencies and the 1uF is a good bypass at medium frequencies.
I always use a 0.1uF ceramic disc capacitor with very short leads directly at the power pins of the 555 and a 100uF capacitor nearby. They smooth the supply current spikes very well.

 

[littletransistor]

A capacitor is used to filter the pin 5 voltage of a 555 when your power supply voltage has mains hum.

National Semi says, "Adequate power supply bypassing is necessary to protect associated circuitry. Minimum recommended is 0.1uF in parallel with 1uF electrolytic."
The 0.1uF ceramic disc is a good bypass capacitor at high frequencies and the 1uF is a good bypass at medium frequencies.
I always use a 0.1uF ceramic disc capacitor with very short leads directly at the power pins of the 555 and a 100uF capacitor nearby. They smooth the supply current spikes very well.

Yeah... I connected the 0.1uF capacitor to the pin 5 and to the ground... is it sufficient? I still need the 555 to drive the CD4017... and the 4017 still misbehaving...

 

[ericgibbs]

hi,
Can you please post a FULL circuit diagram, with pin numbers, lets see how you have got it connected?

 

[audioguru]

Yeah... I connected the 0.1uF capacitor to the pin 5 and to the ground... is it sufficient? I still need the 555 to drive the CD4017... and the 4017 still misbehaving...

No.
The 0.1uF ceramic disc capacitor (plus a 1uF to 100uF electolytic capacitor) must be connected with short leads to bypass the power supply voltage from pin 8 to ground, not pin 5 to ground.

 

[mcs51mc]

One schematic is better than 1000 words (when it's correct of course)

 

[littletransistor]

Okay, here's the full circuit! Not sure why my CD4017 hates my current configurations...

Btw... i'm testing it with 3 LEDs first - so I have to connect the pin 7 (3rd count) to the reset.

 

[ericgibbs]

Okay, here's the full circuit! Not sure why my CD4017 hates my current configurations...

Btw... i'm testing it with 3 LEDs first - so I have to connect the pin 7 (3rd count) to the reset.

IF pin 7 is linked to pin 15 on the 4017, it will only count 0,1,2 !!

So show us how its connected when you want a higher count?

 

[littletransistor]

IF pin 7 is linked to pin 15 on the 4017, it will only count 0,1,2 !!

So show us how its connected when you want a higher count?

Yeah - I'm testing my CD4017 for defects first, so I want it to count 0,1 and 2 first.

Well, if I want a higher count, let's say 6, I'll attach 7 to the pin 15... right?

 

[Roff]

One schematic is better than 1000 words (when it's correct of course)

True. I think yours is worth maybe 2 (Oh, crap!).

 

[ericgibbs]

Yeah - I'm testing my CD4017 for defects first, so I want it to count 0,1 and 2 first.

Well, if I want a higher count, let's say 6, I'll attach 7 to the pin 15... right?

No, pin #6 goes to pin #15

 

[mcs51mc]

True. I think yours is worth maybe 2 (Oh, crap!).

Hi mister know it all better aka Roff aka Ron.
First learn to count 10 - 1.5 = 8.5 = 85%
Crap yourself...

 

[audioguru]

You don't have a supply bypass capacitor at the 555's supply pins. So when its output switches high and causes a 400mA supply current spike, the little 9V battery's voltage drops down to about 5V and the output voltage of the 555 drops down to abput 3.6V which is not high enough to clock the CD4017 that has a bypass capacitor holding its supply voltage at 9V.

 

[Roff]

Hi mister know it all better aka Roff aka Ron.
First learn to count 10 - 1.5 = 8.5 = 85%
Crap yourself...

Lighten up, O thin-skinned one, the two words I was referring to are the ones I utter when I discover that I have made an error:
(1) Oh
(2)crap.

You yourself implied that a schematic will be depreciated in equivalent word value if it is not correct.

I don't understand where your equation comes from.