(Expand for Errata) Previously, we looked at the 8×8 LED Matrix. We noted that, since it needs 16 pins to power, we’ll have to sacrifice quite a lot of pins on the microcontroller. I left this as an open question at the end of that episode, which you can watch here →

In this video, we try to look for ways to cut down on the number of pins, through use of our trusty 74HC595N shift register! We first looked at this nifty little component, which helps store one byte of data, in this video →

By combining two shift registers with the LED Matrix, we can eliminate almost all of the pins used to drive the matrix. What’s even better is, the first shift register can drive the second, reducing our pin count down to just 3.

Want to see the code? Downloads are here:

To download, click “Download” on the left sidebar, and select “Download Repository”.

= ERRATA =
Please note the mistake at 9:10 – In the diagram, the shift and store pins have been reversed. The store pin should be above the shift pin. Thank you very much to Joshua Thyer for pointing out the error!

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29 Comments

Enigma758

January 30, 2020

Great video, I like how you progress from an initial idea to a more optimized design. One question though – at 8:34 the resistors are row based yet at 11:00 your pictures shows them column based.

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Maher Alsayid

January 30, 2020

This is an awesome video thanks for sharing all the good information,
If i want to use an led stripe , do i need to follow the same concept?

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Muthu sundharam

January 30, 2020

very clear

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Aman Agarwal

January 30, 2020

Thanks man! Now i got to know many others are unnecessarily making this concept complicated. Its very difficult to write control code if you are making a 20 X 20 led matrix, the binary for 20 will be very big and you cant use Int as you exceed its limitation, so I used Float. But yours differential control for each shift register is awesome!

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Vise Sphee

January 30, 2020

K

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Tim Scott

January 30, 2020

Could you use this scheme to control a 9px row x 368 column matrix? I'd even be willing to leave a column on the table if I could do this with 47 shift registers, and only 3 data pins.

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Ruan

January 30, 2020

(128 >> i) can be replaced with (1 << (7 – i)) which is preferred for readability.

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Foster Phillips

January 30, 2020

So I'm making a custom Matrix, and I need it to be an 8×9 matrix, I assume I will have to make use of another shift register right?

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Rizky muharman

January 30, 2020

is there a zip file to program ?

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Change starts with the individual

January 30, 2020

Thank you so much!

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Tegan Cirulli

January 30, 2020

Propbably a ridiculous question but how do you know which side is the rows on the led matrix and which side is the columns?

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Armin Arya

January 30, 2020

Can email you I had a few questions from you

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Joshua Thyer

January 30, 2020

at 9:10 you show a pin schematic for the 74HC595N chip labeling 5th pin on the right Shift, and the 6th pin on the right Store.

but  @ 10:06 when you show the 2 chip wiring diagram you switch the Shift and store pins coming from the Arduino signal.

I was just wondering if this was a mistake or something?

Love the content and thanks for the help so far!

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Armin Arya

January 30, 2020

very helpfull. tanks

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اكرم عدنان

January 30, 2020

Thank you so much for this explainining

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Jack the Aviator

January 30, 2020

I built my own 8*8 matrix, and wired it as shown, when I uploaded the code, all of the LEDs were lit. Could you point me in the right direction to debug the issue? And something that I wasn't quite clear on from your video, should enable and reset be pulled high or low?

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gunja203

January 30, 2020

Maybe a noob question but…where do I connect the data, store and shift pin from the shift registor to the arduino ?

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Joseph Rinaldi

January 30, 2020

Fantastic explanation. Very detailed and consise and very clear to understand. One of the best that I have seen so far on youtube. Keep up the exellent work.

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Daryl Seepersad

January 30, 2020

I have a question for you. If I only have resistors on the grounds can I light up all the LEDs at once or will it have to be scanned instead? do i choose the resistor based on 8 Leds in parallel or do i base the resistor on 1 led? For example if the grounds are on the columns and i try to light the whole column vs one led in that column. to light the whole column will i have to scan or can i just send power to all rows ? 8 leds would be on going thru one resistor..

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idris ishola

January 30, 2020

Good mourning, please can I use this code in pic 16f877a

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idris ishola

January 30, 2020

More tutorials my boss

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idris ishola

January 30, 2020

Good tutor. More power to your elbow

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Fantastic Phone

January 30, 2020

excellent video, you make it easy to understand ! Your efforts are greatly appreciated – thank you!

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3DSage

January 30, 2020

Your video was the only one that helped me understand this! Thank you for making this video.

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Zulfan Priangga Fahmi

January 30, 2020

very good explanation! i understand now. but now i donthave idea how that led matrix can show running text. pls make video how to do running text use led matrix. i appreciate it. Thank you!

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max things

January 30, 2020

is there a schematic available somewhre where to read how you connected the 595 with the row and col of the matrix?

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Somnath Bera

January 30, 2020

Thank you

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Владд Брат

January 30, 2020

wery good explanation thank you

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Ham

January 30, 2020

Nice video! There's one thing that I want to ask: can I control one single LED and let it blink, which is a pwm signal output by the register.

Reply

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