Hi.
I am trying to cascade three 4017 counters inorder to light 27 leds and have them constantly run. I have found WEB sites on one 4017 but nothing on how to cascade them. I am using a 555 timer for the clock pulse.
Thanks;
William

 

Connect Carry Out from the first to CE of the second and tie C high.

Repeat for the second and third counters.

Look at the data sheet for the 4017.

EDIT: On re-reading your post, I don't think 3 X 4017 will do what you want.

I assume you want to illuminate only one LED at a time. Is this true?

If so, then you need a modulo 27 counter with suitable decoding.

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Len

 

Modulo 28 is needed. The actual count is one less than the modulo number.

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Creationists have a world of evidence

 

Page 6 of this datasheet from On Semiconductor shows how to do what you want ...
Also, here's the parent MC14017B page ... <link>
JB

*edit* You'll need (4) 4017's to run 27 leds ... 3 will only run 25 ...

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Nothing is impossible for the man who doesn't have to do it himself - Weiler's Law

 

Hi jbeng.
I made a mistake on the count of LEDs I only need 25.
So using four chips is no problem for me but I'll need some help.
also answering Allvols question I am trying to make a light sequencer or light chaser.
Thanks
William

 

That depends upon what he wants.

I assumed he wanted 27 LEDs that turn on in sequence so that there is always one LED lit, he would need a Mod 27, ie. 0 ~ 26.

But if he wants the LEDs to be all off in one state, then he needs a Mod 28.

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Len

 

Following on from my previous post, do you want a "dark state" or do you want one LED lit at all times?

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Len

 

Hi Len
I need one led on all of the time.
Wiliam

 

I assume you want it to be in a continuous sequence, ie. 0, 1, 2, 3, ... 24, 0, etc.

Or do you want it to be in a random sequence? This is more complex.

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Len

 

Hi Len
Yes 1 2 3 4 up to 25 and I need one light on at all times.
William

 

I'll post a circuit tomorrow.

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Len

 

Hi Purcer,

Here's a circuit that will do the trick.
From the first 4017 you use outputs "0" to "8", from the second
4017 you use outputs "1" to "8" and from the third 4017 you use
ouputs "1" to "9" to drive the leds. That's a total of 26 leds. If
you only need 25 outputs, use outputs "1" to "8" from the last
4017 to drive the leds and move the 1 nF capacitor which is
connected to output "0" to output "9". Connect each led with a
suitable resistor in series from each output to ground.

on1aag.

Attached Thumbnails

 

 

Here is my suggestion:-

U1 & U2 are configured as Modulo 5 counters.

The LEDs are arranged in a 5 x 5 matrix.

LED 0 glows when U1 = 0 and U2 = 0.

When either U1 or U2 = 5, the counter is reset rapidly.

U2 is advanced when U1/0 goes high.

I have not included a "power on" reset.

Therefore, since the counters will start in random states when the power is turned on, it may take a few clock pulses before the normal sequence starts.

If you can't buy a 74HC4022 or 74HC4017, let me know and I'll show you how to do it with a 4017, but it will require an extra IC since the 4017 may not have enough current source capability to drive the LEDs.

Choose resistors R0 ~ R4 for the correct LED brightness. For red LEDs, about 470 Ohm should be adequate.

Choose R & C according to the oscillator frequency that you want.

I would make R = 1M and choose C for the frequency you want.

The formula is f = 0.56/(RC) approx. (very approx)

Attached Thumbnails

 

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Len

 

With a 9V battery, the output current from an ordinary 4017 is about 12ma. A current-limiting resistor is not needed for the LEDs. When the battery drops to 6V then the LEDs will appear dimmer.
The absolute max continuous current allowed from the output of a 74HCxx IC is 25mA which looks only slightly brighter than 12mA, a regulated 5V supply is needed and a current-limiting resistor is needed.

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Uncle $crooge

 

Here is a variant on that posted by on1aag.

Note Audio's point about the 4017 and operating the circuit from 9 Volt.

So you could use 4017s with this arrangement.

Attached Thumbnails

 

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Len