Specifically, I want to add multiple relays (approximately 36 to 40) to an Arduino Uno board (using only a few pins). I found a solution using ShiftOut. You can take a look here. But here the example is for testing small LEDs bulbs.

I will control high-voltage electricity like fans, tube lights, washing machine with those relays, so what will be a proper graph or image diagram for that? And if you have any more suggestions for me then you can tell me :) And yes please tell me what I should use for it.

Right now am thinking to use an Arduino, relays, 74HC595 IC only. My diagram for controlling LED is like this:

enter image description here

You can edit it. I just need proper guidance for it and a few good suggestions.

  • Just replace the led/resistor with a relay... repeat as necessary
    – Mazaryk
    May 4 '17 at 18:03
  • Actually am new to arduino. So, Kindly Can You Please tell me with example of 1 relay how to connect it with this bread board properly (just tell me with any 1 relay)
    – rohitcoder
    May 4 '17 at 18:16

If you want to drive a normal magnetic relay you will need to add a transistor / resistor to the output of the 74HC595 as the current is too high across the magnet of the relay to be driven directly by the 74HC595. If you don't want to use a transistor for every relay, you could you an 8 channel driver chip like the ULN2803A. You should be able to connect your relay coil directly from 12v and to the ULN2803A.

Have a look at this page for an example. http://www.mcmajan.com/mcmajanwpr/blog/2014/04/18/arduino-how-to-connect-many-12v-relays-en/

  • 2
    I would strongly recommend ULN2803. They are designed to drive inductive load (motors, relays and so on). And they are so easy to use. For beginners they are best choice.
    – Martynas
    May 4 '17 at 21:48

What about using an I2C I/O expander like MAX7328 or equal and a ULN28XX as relay driver. and you can connect several I/O expanders to the same I2C buss with different addresses.

This will use minimal amount of pins and minimal amount of components.

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