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Topic: LED Sequencer with 4017 chip (Read 2939 times) previous topic - next topic

nicodemus

I currently have a fully functioning piece of code that steps through 8 LEDs via 8 digital pins.  I'd love to take the leap and go up to 64 LEDs but would like to avoid picking up a seeeduino mega board and instead use my current board and save some money.

I'm familiar with 4017 chips and was wondering if it was possible to send each of the arduino's 8 digital pins to their own 4017 chip.  I'm just trying to sort out whether that is or isn't feasible at this point and any insight would be great. Thanks.

Magician

Have you check out playground?
http://arduino.cc/playground/Main/InterfacingWithHardware#LED
May be not exactly 4017, but you can find other design solution that similar to yours,
and would be easy to adapt for your needs.

CrossRoads

CD4017, 10-bit counter chip?
That would work. Apply reset & then start clocking.
Could use the same clock & reset to all parts, separate clock inhibit.
Only problem is that the count is always decoded, so one outut would be active all the time.
Standard shift registers will allow for all outputs to be turned off.

Another option would be a  8x8 matrix driver chip. Then write to it via SPI or I2C and control your LEDs that way.

Or use 2 shift registers laid out in a matrix.
One shift register goes to 8 columns of anodes.
The other goes to 8 rows of cathodes.
Anode High & Cathode low to turn on an LED.
Don't forget 8 current resistors as well.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nicodemus

Thanks Crossroads, that's a great stack of help, I'm sorting through the matrix/multi-plex options, I drifted off into non-LED Arduino projects over the last year and am finding myself rusty now that I'm returning.  I have one quick question, im confused when you say

"Only problem is that the count is always decoded, so one outut would be active all the time."

Do you mean that on the arduino or the 4017 side of things?  Sorry, just a bit confused on that point.


CrossRoads

On the 4017 - one output is always  high.
I guess if you were only using 8 of the 10 bits, then not having LEDs on the 9th & 10th would be the same as off.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nicodemus

that's what I was thinking... I was planning on using the 9 pin as my return to pin 1 the next time that 4017 chip is triggered by the digital out pin of the arduino.  thanks for the help on this, really excited to go home and see it in action.

CrossRoads

http://focus.ti.com/docs/prod/folders/print/cd4017b.html

Not sure I follow you there.
You reset it, out0 goes high.
clock it 8 times, out1 thru out 8 go high.
clock it once more, out 9 goes high.
clock it again, out 0 goes high.
You might be able to use 9 going high as the reset.

Its not like a shift register, there is no input pin to feed it data with.
Unless are we are not discussing the same chip.

You sure you want to us this chip? Looks to me to be too slow to keep up with Arduino.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nicodemus

speed isn't really that critical, i've built similar things out of just 4017's in the past and been more than content with it, just would like to step things up and have the ability to manipulate behavior of the circuit in the future. I'll wire it up this evening and see if I can get the results I'm after, otherwise I'll start taking a look at your other suggestions and go from there. thanks again.

CrossRoads

I was more concerned about required pulse widths & such. Clock needed for example is more than 1 16MHz period long.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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