How to Control a Ton of Inputs using Shift Registers! 

i was making 5*5*5 led cube using 595 shift register and bc 547 transistor. it worked in starting and is not working properly. i have not attached any resistor in the base emitter of transistor and 220 ohms in the collector emitter .CAN THIS BE A PROBLEM. or can you guess...

I was a maestro of IBM 370/390 assembler. You are a maestro of at least Arduino coding. So maybe also C and others. Anyway, I appreciate your coding. Even with the quick hacks you write for these little demos, the code is still tight without being so tight to be incomprehensible like some C/C++ coders like to do. You show off just the right amount. It is easy to understand and "elegant" for demo level programs. I have seen MUCH worse. Thank you for taking the time to do these demos. I understand the electronics and have for decades but your integration with programming is enlightening at the next level of HW/SW integration. Well done.

I'm not an electronic engineer but your explanation was pretty clear. Now i'm ready to solve a problem that seemed very complicated to me before watching this great video. Thanks!

yes, you have a good point, and I just added an annotation, but this does allow you to mix inputs and outputs in the same shift register bank

Brilliant! Provision for debounce, (frequently not the case with shift register videos). Plus SPI library for speed. Lots of lateral thinking here. Earned you a subscription

Perfect. I was looking for a way to use BCD switches as inputs to Arduino and you have shown me the way.

*Very nice, I actually under stand shift registers a lot better now!! Specifically the 74HC595!! Thanks!!!*

nice one! Thanks for the tip. I was just goofing around with these

This is really great. Thanks. It would be good to see how you wired everything up when you do these.

I am 2 minutes in and I already know I am going to subscribe. This guy is soooo good. Like butter. Thank you Kevin. Your presentation is just flawless and perfect. I cannot wait to watch many of your videos. Thank you so much. I am fan.

Thank you so much for this video! you answered a lot of questions I had for my pinball project.

Very efficient way to sense the actuation of any one or more of a number of buttons. Great. You are basically setting each button on a single bit then polling all the bits in the byte to see which one are on or off.

Cheers Kevin, you did a better video explaining this technique than in possibly could.

Thanks alot for the explanation. I was wondering if you have the part numbers for the diodes you used?

Hey I appreciate the video, but it would be very helpful to beginners like myself to have a schematic. Is there a wiring diagram that you could share with us??

Just want to say man, really good video very clear and understandable you have a great channel

yea, I know... I need to do that. Many people have suggested the same. Just been really busy lately

Awesome tutorial, any chance i can get a schematic.. been at it for a week and i just cant get it to work. I am from South Africa, not sure where i am going wrong... difference in IC maybe... PS i am still a newbie, what is the best way of trouble shooting where i am going wrong?

Kevin, how is this wired? I'm having problems getting this set up. Thanks.

Great Video ! I want to use a Rotary Encoder and need the Interrupt for this one. But I could use any PinChangeInterrrupt for checking any pressed button, right ? Greetings from Austria !

I'm looking for something similar but I need to press a button and it will turn off the other. it's possible?

thank you so much Kevin for that awesome video, can you do another for 74HC165? it would really helpful. thank you.

Hi! Does all this can work on a raspberry pi (and domoticz)? Thanks :)

How would you apply the same principle for an analog signal ? The Arduino has only 6 analog inputs, what could we use to extend that to say 20+ analog inputs?

Have you tried connecting this to the arduino in your cube to change the animation that is running?

Hi. I have a working circuit which has 4 digit 7 segment led display. I want to to read the Data and make my arduino send Smae numbers to my serial monitor tgat what my segment display shows simultaneously. What u wld advice? And umm this segment display has total 12 inputs which 8 for leds and 4 for shifting from eacg 1 number block cathodes(or anodes). Any advice?

yep this will work for you... sounds like an awesome project! You may want to review the other comments below to see what others have suggested

Do you have schematics/diagrams for the connections please?

Is there a reason why I can't get my led circuit, the circuit is from a double ended light saber thing that have I think 6 leds on one circuit that has one + cable for each and one - cable for all of them.

As you had as a baloon at the start, a parallel in serial out is the way ti go for input. 3 pins, clock, load & data. cheers

I am relativity new to programming shift registers. How could I modify this code to use only 1 register for inputs and then do something like print "high" to the serial monitor?

very nice video. i only have a basic knowledge of what different components do and i was able to understand this very clearly

Methinks an array or two would help to clean up the code. You could remove the while loop at the end and repeat the pin read function without actually writing to the leds. Run pin_read, get an array for which buttons are pressed, compare it to the array for the buttons which were previously pressed. From that you can find which buttons have gone from 0 to 1. If nothing's changed, there's no difference, so pin_read can just keep looping while the input is high.

Tq for the detail explanation,..about to build something and learning for shift reg, already watch many vid n good input

yes you are right! Ha, this actually got me as well! will update the code

Can a automatic style casino keno game be made up with Arduino or some micro controller. It would show game number as well as drawing 20 random numbers out of 80 leds.

Thank you. I now more fully understand how CCDs work by shifting the data.

Thank you so much Kevin. Please i need the diagram?

I am just getting into Arduino, but have experience with programming. I was just wondering about your code a bit. I was thinking that it may be better to make pen_read set a global boolean, then in your loop you would do basically what you are doing in pen_read right now. loop would be while(pressed) { *current_pen_read_code*; pressed = false; }; Like I said, I am new, and don't have the parts to test this yet. Can you think of why that would not work, or why that would be less effective?

Erhm honestly thanks for showing that circuit with the analogRead at the start. That'll actually do for my project since it's only 4 buttons I'm using and they shouldn't/can't be pressed at the same time in my interface. I'll definitely start playing with shift registers in the future though when time is a less pressing issue :P

Hi Kevin ! I'm working on a project using your setup (actually, using the "piano" version as it's exactly what I'm trying to achieve), and I can't figure out something. I don't get the usage and difference between the data and what you call "Input from the buttons" (pin 2). What exactly is this pin 2 doing and how to connect it to my buttons ? We can't really see the board or schematics in your video :/ Thanks !

@kevin darrah sir im asking for help do you have a schematic diagram of 4 or 5 or more inputs interlocking circuits...for example i have a four inputs push button 1 to 4 and output LED 1 to 4 the sequence is like this..if i press push button 4 the LED4 will turn on then when i press push button 1 the LED 4 will turn off then the LED 1 will turn on then when i press push button 3 the LED 1 will turn off then LED 3 will turn on and so on..it always one LED will acivate on OUTPUT...please...thanks in advance

Thanks, that was very helpful!!!

Just wondering if you could offer suggestions as to why this code works on an UNO but not on a mega2650? I've tried changing the pins in the code to the appropriate MOSI and SCK pins on the mega but still no luck. Any help appreciated

thanks. clear video on how it works. but i'm not familiar with SPI, so the code is a little hard to understand.

Good explanation of good design. Cinematography should be front lighting to remove glare from back light on desktop.

my code was to simply toggle the LED on or off, but if you just need to read the value in as being just on or OFF, that is simple, since a double tap wouldn't affect you. Like the ISR being called would not flip your output

Hi Kevin .I am working on project where I need to switch on /off 16 LED with 16 switch with Arduino uno.Could you please show me how to edit the code for 16l LED's whit 16 switches

Hi Kevin, I am trying to figure out how to make simple led selection indicator, so I want 8 LED to be shifted in an infinite loop by a press of a button. So one press next LED is lit, another press next to last LED is lit and so on in circle. I hope you understand what I want to do. Please help, thank you :)

Love your work!

Great video, Thanks for sharing!

Good button technique but all those delays in an ISR is very bad practice. You should only record the state of the buttons into variables and let the main loop process debounce and determine if the buttons have been pressed. Another way is to check a clock state and determine if the button has been pressed long enough in the ISR and set a state. The objective is to manage the button state as quickly as possible in the ISR and return to the main loop (rest of the code).

Hello Mr.Darrah , Kevin , First of all , congratulations for you excellent job. That being said , I wonder if you can post a tutorial with the wiring diagram of the circuit, because I tried several times and could not make it work. Thank you in advance. Wagner Hiroshi

Amazing technique!

first he says he's going to assume we understand how shift registers work and then he says "I'm sure if you guys are familiar with diodes or not" haha I appreciate you explaining everything

I couldn't find schematics for this in your site! are those published anywhere else? :O :O

Thanks man. Really helpful !

hmmm, maybe? I think there might be a way to modify what I have here for something like that, but this is interrupt driven, so if you only care about a reading above a threshold then yea, I think this coudl work

This did blow my mind, it was so awesome. I could have never imagined such an amazing technique was even possible.

I think you just inspired me to make a followup video!

Cool trick! I was thinking of letting the last output shift everything back to the micro controller. As in insted of connecting another shift register in series, I would connect it back to the arduino in this case. There I would shift the bits into a byte and after the 8 clocks I would have the output byte back and could mask for the correct buttonpress. I figured it would maybe work since it shifts out from there. But maybe your loop is better hmm I'll try and see. This gave me inspiration! Thanx

hello, can you please put a fritzing picture or a schematic for the circuit ?

u can use data lactches for same porpose. 74hc374 no code needed. just use external data read command 74138 demultiplexer will also help u for more inputs

As any arduino board all pins can be used as digitalRead. My arduino Pro micro board has 18 pins for use as digitalRead. I Need to 42 pins for input to my arduino board(for different outputs) . Is it possible using 74HC595 shift register????? . If yes, please help me with arduino sketch & wiring diagram arduino board to 74HC595 and push buttons,,,,,,,

The buttons you are using here, are they not giving you any bounceproblems?, if so, what buttons are they?

I was going to ask why you didn't use a regular parallel in - serial out shiftregister but since multiple people already asked it I'm not going to ask it again.) It's actually a pretty neat technique that I've never seen before so thank you for explaining it. Using outputs as inputs if that's not thinking outside of the box, I don't know what is. Great video, as always.

Can it be used for analog readings? :)

Complete awesomeness! Thank you.

Hey, I'm curious. What microcontroller are you using in this video?

The while loop at the end of the ISR should not be necessary, if the IRS is only called on the rising edge. And if you did want to improve your code(or make it shorter) you could also replace the whole check variable by replacing it with "1

hi, are you using two 74HC595 for both controlling inputs and outputs? and is it possible to have the circuit schematic of this tutorial?

Hi, Very useful information. I wasn't needing thousands but I am going to be making a control panel for a spaceship game I play to make it more interesting to play than just keyboard. Going to use different switches and types of lights. Was probably needing about 20 inputs and more outputs. Was going to add extra just to give it more of a spaceship feel too :) I thought I was going to have to use analog multiplexers for input but I guess I can just use the shift registers now.

So what happens if you're holding down one button and then press another? I'd assume that while loop at the end screws you over a bit there.

exellent thats the best tutorial ever been made

Thank God. Finaly found what i've needed!

Hi there, Has anybody got any tips/ advice for a relative beginner in electronics? I've got some basic knowledge about basic components(leds, resistors, caps) and the picaxe system. But I was wondering if there are any good websites or other resources that could help me broaden my knowledge/ understanding and work with more complex things with more integrated circuits driving a wider variety of outputs. Thanks.

What pushbutton are you using?

This is so cool! Thanks for explaining! And also: Fix your indentation!!! :-P

yea they are, but no prob since we are debouncing in software. A simple delay is all that's needed

You are the best dude!!

I was about to post the same question. The 74HC595 is a Serial to Serial/Parallel IC, I'd use a Parallel to Serial IC with internal pull-up resistors.

Could you please post schematic of this circuit on your website. I understand shift registers pretty well but I'm a bit confused how you wired this project up.

Hi bro we need circuit diagram for this project

Isn't this simplier with the CD4021 chip instead of the 74HC595 chip? I'm a novice so I really don't know, but it does seem like one chip is made to shift out (e.g., to a bunch of LEDs) and another to shift in (e.g., many buttons) On the other hand most arduino kits come with a 74HC595 and not a CD4021 so maybe I'm missing something.

Awsome tutorial

Yes, this is an old thread, but still very, very useful. The technique to find out which buttons are pressed is super! And this, with a 595 which is supposed to drive something, not to (indirectly) detect if something is changed/pressed... Very clever indeed... Problem is that I don't know which Arduino has been used for this demo (if an Arduino has been used at all) but I struggled with the SPI communication because with the Arduino Uno, the clock and data pins are switched. In my case, the clock pin is Arduino pin 13 (and not 11 as per the tutorial) and the MOSI pin is Arduino pin 11 (and not 13 as per the tutorial). In the video where the code is explained (e.g. time 12.14) it's mentioned otherwise. Unless the comment written next to the pins is wrong, in which case I step back silently... Can this be confirmed? Best, --Geert

This is remarkably similar to how a Diode Matrix Rom works. Very clever!

Would this work? bitWrite(Output,j,1-bitRead(Output,j)) Because 1-bitRead(Output,j) changes 0 into 1 (and 1 into 0).

I think u can also use a 74165 parallel in serial out that has its output pin hooked to DS of the 74595 to achieve this

Kevin, I would like to discuss one idea with you. How could I contact you?

could you please show me a schematic of how i would connect 8 switches(input) to my 74HC165 to Arduino and then to my 74HC595 to my 8 LEDs(output)?When a correspong switch is off, then a corresponding LED should go on

Can anyone help with what change to the code is necessary to control 16 leds with 16 push buttons.

Diodes are like check valves, they only allow current to flow in one direction..

how many shift registers I need to control 25 key keyboard ? what is scan matrix? with 9*3 scan matrix can I control all 25 keys . how to set up that? pls advise

The diodes are required if anyone is wondering :) I didn't have any on hand so I just used some LEDs! for testing purposes, anyways.

Hi Kevin, I'm trying to make a small simple midi keyboard with 25keys (nothing fancy, just digital switches reading on and offs and sending the data to the computer) . I just need it to be polyphonic upto 10keys. I.e it should be able to detect (on or off) for 10 keys at them same time. And it should be very responsive in reading it. Are multiplexers okay or shift registers? Which shift register do I need need. And i saw you pressing multiple buttons at once. How many can actually be pressed at the same time and still work in your setup.

There is another problem with this idea, if you want to use some digital sensors to use instead of switches and all or any two sensors read at the same time, then it will be wrong reading. Isnt it?

Great idea BOSS!

It would really be helpful if you upload the circuit schematic

Can u make a small launchpad using this plz