Good evening,
I am hoping to get a clear answer on this as I have read many posts but haven't come to a conclusion yet. This thread will be ongoing.
I want to connect several 10A outputs to my Arduino UNO and may exceed 20 outputs. I am going to create relay circuits using transistors or MOSFETs to drive the relays and use the Arduino to drive the MOSFETS.
How do I go about adding more outputs to my Arduino so that I can drive them all safely? I also want to make them come on sequentially for 3-5 seconds. Be patient with me please. All new in this area. Thank you for your time.
Hello @bwilliams60 and welcome!
I would suggest you draw a schematic as that will be easier to understand.
What does this mean 
?
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Makes no sense. An Arduino input needs microamps.
Now we´re getting somewhere.
Using logic level N channel MOSFETS switching the low side of the load will manage most everything. Another approach could be using relay modules having an opto interface towards the Arduino. Do know that relays has a limited amount of action. Using SSR, Solid State Relays would have a much longer life.
To add more outputs either use a Mega or use external I/O expander circuits/boards.
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Firstly, are these 20A loads 115VAC circuits, or 12VDC? Makes a big difference!
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Thank you for the replies so far.
So the outputs are going to need to drive several 12V, up to 10A outputs. Most will be lights but some could be small motors and again, only for a short duration, maybe 3-5 seconds just to ensure that the circuit I am testing, works.
I like the idea of using the logic level N-channel MOSFETS over the relays. It seems like an easy solution and less space.
My next thing is to activate the outputs sequentially, which I believe to be programming. I have very limited experience in this and this is where I will need the most help.
Lastly, is the number of outputs. I would like to know the best way to expand the number of outputs from the Arduino. Perhaps a shift register would help me here?
So far so good, thank you again for your help so far.
Are there any good freewares for drawing Arduino projects?
Why not buy a mega that has more output pins?
An i/o expander might be an alternative.
Since you are not working with mains, the mosfets will be fine.
Hello bwilliams60
Take a view for a tutorial here:
https://create.arduino.cc/projecthub/tarantula3/driving-a-relay-with-an-arduino-722c24
I'd keep the power lines distant from the Arduino. Have shift registers or port expanders and MOSFETs near the loads. Adding optocouplers to the bus lines makes these lines less susceptible to EMF and noise.
So a relay that can handle 10A DC at 12V s not cheap. You can't run a relay at the maximum rating you have to allow at least 20% more capacity that you use.
But more important is the fact that you can't simply scale up an Arduino project to handle 200 Amps of current. What will happen is that when you turn off a relay carrying that amount of current, you will get arcking causing electromagnetic interference which most probably will reset the Arduino.
It is a skilled job to get these things tamed and not one for a beginner. It is not a case of what you should do to stop it, there are many variables including how you physically lay out your components, what the grounding tracks are like, and interaction with the power supply.
For examples of how people have overcome this or even not overcome this please search the forum, it is a common problem.
I would start with searching for
Arduino resets when relay turns off.
Also see
Snubbers
This is because it is a complex question and there are no simple answers.
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