Powering Arduink from power line to run motors

Dear all,

I am working on a project in which I would like to use Adafruit motor shield torun three to four DC engines. I would like to have the device powered from power line via adaptor; but I am wondering ho to power arduino and motors separately (I’v heard it is necessary to avoid noise)using just power line energy. How to do it?

What voltage and power are the motors?

1200 mA, 5V

So stall current is probably 5 to 10A range.

Any supply that can provide around 5A continuous and tolerates temporary overload without cutting out would do. For instance a 6V lead-acid battery would be quite good.

For mains supplies you have to worry about cut-out behaviour - lots of supplies react to overload by cutting out completely - which doesn't play nicely with stall current spikes. You can just go for the over-engineered approach (supply can handle stall current easily), or be careful in ramping up PWM levels to each motor to avoid large stall currents flowing.

Yes, definitely a separate supply for the motors (for several reasons), common the grounds. A USB charger is a good way to power the Arduino, and note that the two supplies are going to have grounds commoned, usually this isn't a problem, either they will be isolated or mains earth will already be connected to the 0V output.

Thank you for answer! Yet the problem is that I would like to avoid any kind of battery - could I in priniciple use USB charger to power Arduino and sth like that - https://i0.wp.com/www.open-electronics.org/wp-content/uploads/2015/07/Fig4.png to power motors via jack?

The transformer based supply is going to handle temporary overload OK, ie not shutting off, so its more
motor-friendly that many. Just check that you don’t overload it continuously, and you can monitor the output
voltage to see if its coping well (gross overload will not be good, fuse will typically blow, and it may not be
user-servicable)