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Running light using 4017

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RajivConfident

RajivConfident

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i have a circuit of running light using 4017 and 555 ICwhich has 8 output terminals.But I want more output by using same ICs.
Is it possible to make more output i.e nearly 20 to 25 output.
if additional circuit(without using other ICs) is required please send me.
 

Hi,

The datasheets have a cascading circuit, NXP HEF4017B figure 11, and TI CD4017 figure 19, they use additional ICs. Don't know a way to get 25 sequential outputs from only 8 outputs with no additional ICs.

If you didn't mean 25 steps of light, and mean 8 steps that power a total of 25 lights, then you can reduce the current drawn by 3 LEDs/lights in series or parallel to fit what the 4017 can provide at any one time according to the datasheet electrical specifications.
 

Here is how to cascade three CD4017 ICs to get 25 outputs in sequence:
 

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It should be possible to multiplex two rows of led's. Provide a path to ground for one row (for ten pulses), then provide ground for the other row (for ten pulses). This is similar to the method of multiplexing alphanumeric displays.
 

BradtheRad said:
D flip flop wired as a 'divide by 2' counter.
Click to expand...
Then most turned off LEDs have reversed polarity which might cause leakage current to light the LED on the other row that should be turned off.

In my LED Chaser project I use a transistor to pulse each LED for a short duration to reduce battery power. Then when one LED is turned on the others have reversed polarity but I frequently had LEDs leaking reverse current which dimly lighted the LED that just turned off and it should stay dark. I fixed my "leaky LEDs" by connecting a Schottky diode in series with each one. They were high quality HP Agilent LEDs.
 

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Are you sure you only want 1 of 25 LEDs on at one time or some other arbitrary pattern?
Maybe you want 2 or more sequential out of 25 on at a time, then you would use 3 cascaded SIPO registers with an input seed pattern and feedback loop.
 

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