Go Down

Topic: How many relay can use by a single arduino. (Read 314 times) previous topic - next topic

moseurbsl

Hi, I am new with arduino. Recently I came up with the idea of make a home automation system for my own. Suddenly I realized, I don't know how many relay can used by a single "arduino uno" or other arduino.
Please help me. I need details.


1 which arduino I should use?
2 how many relay I can use?
3 if anyone have any better idea for home automation system, and if it is possible please share with me.

ardy_guy

An opto-isolated relay uses no more Arduino current than an led, since that's exactly what they are, if you wire them to use an external supply for the relay coil.

Not sure exactly what they draw, just a couple of mA according to this (bottom left of scheatic), so you can run a large number before you draw significant current. But you really do need a separate supply to the relay coil a) for isolation and b) so you're not powering the relay from the Arduino, only controlling it with tiny current.
[irishAccent]Have you tried turning it off and on again?[/irishAccent]

Grumpy_Mike

Basically you can drive as many as you want. If you want more than the number of pins on the Arduino simply use a chain of shift registers to expand the output.

moseurbsl

If you want more than the number of pins on the Arduino simply use a chain of shift registers to expand the output.
Thank you for you reply.


I am new with arduino. So I don't know lots of things.
I want make a home automation system. I want control all af my house staff through my Android phone.
But I think my uno can controll only 10/12 relay.

"You are speaking about expand the output."
I don't know how. And I don't know how this  expanding going to work for my project.
If u have anything that show me how? That will be very helpful for me.

Once again, thank you.


Grumpy_Mike

Quote
I don't know how. And I don't know how this  expanding going to work for my project.
Have you read How to use this forum it will tell you what to do with answers. In this case I advised you to use a shift register so I would have expected you to use google to look up:-
Arduino shift register.

You would have found this link:- https://www.arduino.cc/en/tutorial/ShiftOut

CrossRoads

#5
Apr 03, 2017, 09:46 pm Last Edit: Apr 03, 2017, 09:47 pm by CrossRoads
Here's a relay card I offer, the coils are controlled by putting data into a shift register. You can daisy chain the cards, or you send data to each one independently.
http://www.crossroadsfencing.com/BobuinoRev17/
As an Uno shield

As a standalone card

3 daisychained
https://www.youtube.com/watch?v=oHTRGXyd3xU
Driving 120V LED light strings
https://www.youtube.com/watch?v=ukRtgLK_b5c

Course, this does require all your power sources to be controlled from one place. Is that what you want? Or do you want 1 and 2 relays scattered around the house? Perhaps a bunch of Arduino equivalents connected up via RS485 to a master, with each controlling 1 to several relays?
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.

DVDdoug

Quote
I want make a home automation system. I want control all af my house staff through my Android phone.
But I think my uno can controll only 10/12 relay.
I'd suggest you look into some of the existing home automation systems.   With dimmer switches and controlled power outlets like these you won't have to re-wire your house, and the dimmers & switches can still operate locally/manually.

With these systems you don't directly communicate with the switches/outlets over the Internet or the cell phone network, but you can get (or build) a "bridge" or "hub"  that communicates with the switches/outlets and with a Wi-Fi or the cell network, etc.    

If you really want to build something yourself, you can build a compatible controller with the Arduino.   But, you will have to make it compatible with whatever protocol your switches/outlets use.

And, if you choose one of the standard home automation protocols it will be easier to upgrade or modify your setup.

SmartHome.com sells lots of home automation products if you want to get an idea of what's available.

moseurbsl

Have you read How to use this forum it will tell you what to do with answers. In this case I advised you to use a shift register so I would have expected you to use google to look up:-
Arduino shift register.

You would have found this link:- https://www.arduino.cc/en/tutorial/ShiftOut
No I didn't read How to use this forum before your answer.
And yes I did use google for find some information about Arduino shift register.
However, thank you.

lastchancename

Before you connect ANY mains powered devices to an Arduino or relay board, make sure you understand the concepts of isolation, grounding and PCB creepage.
The alternative is rarely pretty.
Q: How many searches did you make before posting this question?      A: none
At the very least, take a guess at the solution, then we can help move forward from what you know already.

moseurbsl

Yes I did search,  but I think I didn't search the right way.
After creating this post I found this
https://www.instructables.com/id/3-Arduino-pins-to-24-output-pins/


Look I know I am not as fast as you are. But I can use google. The real problem is you can't understand my problem.

I am from Bangladesh. From my country I can't order ebay.com or amazon.com or any other shop otside my country. Sometimes I even couldn't find all parts.  So I need find an alternative way almost every time.

I know you ar busy lot more than me. But I am really happy for all of your help.

Grumpy_Mike

Quote
The real problem is you can't understand my problem.
And who's fault is that?

Quote
From my country I can't order ebay.com or amazon.com or any other shop otside my country.
It would be good to state these things in the first post.

However I am not sure how this is going to help us help you. How do we know what parts you can get in your country unless you tell us where you can get parts.

moseurbsl

It's  ok.
Actually I want make a home automation system, which I want control by my mobile phone. I searched on google, then I found some post about arduono. Likely I found a clone on a local online tech shop. From Then I am trying to gather as much information as I can.

Now I have
1: arduino
2: relay bord
3: 3.3/5 volt power
4: bt hc 05 (without base board)



Go Up