RS485 multiple nano stepper motor setup power supply

Guys, I have been trying to put together a setup for some gauges driven by stepper motors, using the DCS Bios program. I can make individual units work, so that each nano is connected via a usb cable, but am struggling with turning this into an RS485 network.

One of the problems i have is with the power supply.

The putative setup is as follows on the attached schematic (note I am aware that the lines linking the two MAX487 chips are crossed)

1 Arduino Mega as the RS485 Master. This is connected via usb to the pc, and to a MAX487 chip, plus a 12v power supply to the VIN and GND pins

The 12v supply is shared by the slave arduino nanos using the VIN and GND pins, and by the easy driver board via the M+ and GND pins.

When I connect using the principles of that schematic, the Mega board gets very very hot near the usb connection. The stepper motor setup that worked fine as standalone stops working when the RS485 is connected up. Obviously the Nano is no longer connected to the usb, and I assume it is powered by the 12v supply, and that is converted to 5v by the nano for the MAX487 chips

The power supply I’m using is an old Acer 12v dc laptop powerpack, so I’m pretty confident it’s a stable supply.

Would it be better to use a separate 12v supply for the stepper driver board, and use a lower (5v?) Power supply for the Arduinos?

Cheers

Les

RS485 schematic.pdf (81.4 KB)

When I connect using the principles of that schematic, the Mega board gets very very hot near the usb connection.

Try to use a 9V power supply or just split those 12V with a 7805 to just power the arduinos and the max's.
Stepper motor could drain some current ...

he stepper motor setup that worked fine as standalone stops working when the RS485 is connected up.

How are you making the communications of the max's?
RS485 is a half-duplex communication protocol, show us how you are passing data between the nodes.

Thanks for the reply Hogo.

As for the way that the nodes pass data, I'm sorry to say that my electronic skills are not good enough to bevable to answer that. Does the schematic not show that in any way? I apologise, you are trying to help me and I'm unable to answer!

As for the orginal question, I saw an interesting discussion on another thread that maybe partly answers this. It seems that the VIN pin is a legacy, ( Does the Nano IO board have a regulator of its own? - General Electronics - Arduino Forum ) and that using the 5v pin and a regulated phone charger is the way to go

Anyway, let me know how I can answer the packet thing, anything that can help me understand better has got to be a good thing

Cheers

Les