Powering Arduino from 12v and then a MAX487CPA from Arduino 5v?

[maciekish]

Hi, I'm designing some PCBs for my cockpit and im trying to cut down on unnecessary components. I currently have an L7805CV converting 12v to 5v for my Ardiuno and MAX487CPA RS485 chip. If i remove the L7805CV voltage regulator and connect 12v to VIN on the Arduino, and the MAX487CPA VCC pin to 5V on the Arduino, it works, but the question is is this sustainable? How much power does a MAX487CPA draw, will it slowly kill the Arduino? Photo just for reference, it is with the L7805CV.

[No1sonuk]

Should be OK.
As far as I can see, the MAX487 draws a couple of mA in normal operation.
As for the current the Nano can supply, the second answer here is interesting:
https://arduino.stackexchange.com/questions/35121/max-current-of-vin-and-5v-pin-on-arduino-nano
Because of the heat the regulator has to dissipate, you could draw more current from the Nano if you used 9V or 7V VIN.

If you're running RS485 about anyway, why not run a 5V rail with it?  Have a decent current regulator or two in central location(s) that you can fan cool and run 5V with the RS485 - That's how I designed my Nano breakout.
I included a 4-wire RS485 bus:- 5V, GND, two signal.

[maciekish]

Thanks for the idea. The reason i dont want to run a 5v rail is i already need a 12v rail for leds so i was considering 12v, gnd, a & b wires on a long bus that runs around the cockpit, with the arduino 5vrr to power tiny custom pcbs with a max487 + tip120 for each panel in the cockpit.