Grounding between 12v power source, voltage converters and Arduino

Projects General Guidance
1

Hello everyone, I am new to arduino and electronics and I am going through a steep learning curve.

I am using an Arduino MEGA 2560 rev3 with a terminal block adapter and I am trying to build a DAQ system. In the system there are circuits using 5v, 12v, and 24v.

  • I am using 12v into the Vin to power the board and have connected the GND on the arduino to the GND of the 12v supply.
  • I am powering 7x MAX31865, 2x NAU 7802 chips, and 2x DFRobot High Temperature chips in parallel with the 5v pin of the arduino and grounding them back to the arduino GND.
  • I am powering 9x intrinsic barriers that connect between the 7x MAX31865 and 2x DFRobot chips and their sensors, as well as a relay that uses 24v, using a 12v to 24v converter for power. I have grounded the barriers to the 24v ground and the relay to both the 24v ground and arduino ground.

Currently the setup works well and I can read values properly. But I noticed that the arduino's 5v voltage regulator gets really hot (most likely due to powering many chips) which I would like to avoid. I am trying to power the chips through a 12v to 5v converter instead with a higher power rating. When I wire it, everything powers normally but the readings I get are all messed up.

I am suspecting that it has to do with grounding of the 5v circuit (signal lines are going to arduino board but power is through 5v conveter) but I am not sure what is wrong. When I connect the 5v side or the 12v side of the converter ground to the arduino ground it still does not fix the problem. Below is a simplified sketch of the full scale wiring diagram that depicts the way that the powers and grounds are wired. It excludes most chips but the idea should be there.

Any input would be greatly appreciated!

IMG_5368

2

With 12v to Vin the Arduino voltage regulator has 7 volts dropped across it, that’s the problem.

Vin is recommended to be 7 to 9V.

3

Thanks for the schematic!

Good. That's necessary. Note the reply from @LarryD.

That is likely not good. The Arduino 5 volt converter might get overheated. Sum up the need of current for those 5 volt devices! More then some 20 mA and You're in trouble.

This is not a project to land a man on the moon but more precise information then words is needed. Please post datasheets for those less well known circuits.

4

Thank you for your response! Do you see anything wrong with the schematic? I was working with the 5v from the board which I am learning it is a bad idea. Besides changing the 5v power source to the converter nothing has changed so it should be something with common grounding

5

Not much current to ger from it. 20 - 50 mA maybe.

What converter do You think about? Get a good external 5 volt supply!

6

You have a 12v to 5v converter in your circuit already, I suggest you power the Mega from that to its 5v pin.

7

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