Quick Question Regarding 2 Arduinos and One Power Supply

Hello,

I will be powering 2 Arduino Mega’s (one master and one slave) and I would like to power them using a single power supply (either a 9V 5A or a 12V 5A). Which one should I use.

I know 5A may seem like overkill, but my Arduino’s will be connected to a lot of modules and other electronics, so I’d rather have a little extra amperage just sitting there, just in case.

Thanks in advance.

9v 5A

12V 5A

Use a splitter power cable and power them both from one supply. 9V, or 7.5V even, will make like easier on the 5V regulator.
Example

Or wire a couple of these in parallel

Or cut one of these in half and wire in parallel

Or use 2 USB cables and get 5V power from a dual USB outlet phone charger.

Wall outlet type

Benchtop

Or vehicle

Lot of options.

Ok, thanks.

I know the Arduino can work using 7-12V, will 12V overheat the Arduino’s? Or am i better off just using 9V?

Neither, of course! :roll_eyes:

Arduinos operate on 5 V, not 9 or 12. “Vin” or the “barrel jack” is useless since the on-board regulator can only handle of the order of 100 mA before overheating and shutting down, hopefully reversibly. So powering this way with anything more than a 200 mA power supply is totally useless.

You need to connect a 5 V power supply to the “5V” pin and ground of each. But you will need to disconnect (only) the 5 V pin when you connect to a PC via the USB port in order to avoid back-feeding the PC USB system.

Ok.
I’ve been using a 9V 2A power supply (with barrel jack) on an Arduino mega and I haven’t had any problems. I was just looking to upgrade from the 9V 2A to 9V/12V 5A (becuase I though they would need more amperage) but I guess the 9V 2A should be able to power both Arduino’s them since they can only handle 100ma. Correct?

Bud did you not say?

So how are you going to power all the other things you connect - which presumably will require 5 V?

1A/Arduino is plenty.
The lower the supply voltage the better to help with 5V regulator cooling.

Through the Arduino. I’m just wondering what to use to supply power to the Arduino through the barrel jack.

Ok, thanks.

I did also plan add some fans to help everything cool down.

1A/Arduino is plenty.
The lower the supply voltage the better to help with 5V regulator cooling.

So if in the future I wanted to connect more Arduinos together like 3-4 then I I would need more amperage, correct?

Also (this is a bit off topic) Is it possible to connect different Arduino’s together? Like an Arduino Mega (Master) and an Arduino Mega (Slave) plus an Arduino Uno and Nano (slave).

Oh, for goodness’ sake, just don’t! :roll_eyes: The “barrel jack” is basically useless if you plan to connect anything else to the Arduino.

Ok. So I should just use a 5V power supply and connect it to Vin and GND on each of my Arduinos? Would that mean a 5V 5A or greater power supply should work then?

But you will need to disconnect (only) the 5 V pin when you connect to a PC via the USB port in order to avoid back-feeding the PC USB system.

Also could I add a diode on the 5V pin so when I connect to to my PC it would prevent back feed, or will that not work?

So - forget that the “Vin” pin - or the “barrel jack” exists! They are useless!

A 5 V supply connected to the “5V” pin on the Arduino will power it for as much current it requires, which is only the current required by the chips plus whatever current (limited to 20 mA per pin and a certain limit per “port” group) the things you have connected to the ports, draw. So your 5 V supply will power multiple Arduinos and will also connect to all the other modules requiring 5 V.

The “backfeed” problem is just part of the UNO, Mega 2560 or Leonardo; the Nano incorporates a diode in the internal position which does prevent it. As I pointed out, you just need to disconnect (only) the 5 V pin when you connect to a PC via the USB port .

As to your other concerns, it clearly is possible to connect many Arduinox together, but you do introduce problems in designing communication protocols between them. Why would you want more than one Arduino? If you need more complex code with more memory you are better off to go to an ESP device or a more capable processor in general.

The regulator on your arduino MEGA determines how much current it can supply. I wouldn’t say any values such as “order of 100mA” unless I see the spec sheet. So google your regulator module.

In the old days, I believe some 269 series of linear regulators were used, with a minimal rating of 800mA. Later there was an Arduino SRL and some of their MEGA2560 (around 2013) were equipped with low-quality regulators, with a backward C logo. Under no load except idle load of mega2560 and 12V dc, it will go into thermal shutdown after a few minutes. I only realized it when winter turned into summer and some outdoor data loggers started acting up. So later Arduino LLC MEGA2560s are equipped with 7CE50 series of linear regulators. They are rated for at least 1A so I’ve not had issues with those using 12V DC, including their clones using the same regulators.

If you power your arduino with 5V power bank, then going through the USB port will cause a small fraction of a volt of drop due to an on board diode. Decent computers and hubs have mechanisms to prevent current flowing into your USB port but I don’t see decent USB hubs anywhere and I question how much computer makers try to save money by not employing such protection.

But no heatsink, so the nominal rating of the regulator is meaningless (or perhaps better expressed, irrelevant!). :roll_eyes:

Unless it is a UNO, Mega2560 or Leonardo.

These have a “polyfuse” and FET switch.

Most powered USB hubs, even major brands, indeed connect the 5 V straight back into the PC USB port. :roll_eyes:

Alright. So I will use a 5V 10A power supply that I have, and connect it to the 5v pin and GND, and from that 5v pin I will connect it to the positive breadboard bus to power all my other modules.

The “backfeed” problem is just part of the UNO, Mega 2560 or Leonardo; the Nano incorporates a diode in the internal position which does prevent it. As I pointed out, you just need to disconnect (only) the 5 V pin when you connect to a PC via the USB port.

I will be storing my Arduino in a box that I don’t want to open every time I upload new code (I have an external usb port where I plug in a male to male usb from that port to my computer in order to upload new code. The other end of that external usb port is connected to the male end of the arduino cable ).

So will a standard diode work do I need something special?

Also, I am using a Movi Shield and one of it’s requirements are that it needs 7-16v that must be powered through the arduino.

Requirements
Before you get started, you will need the following items to use your MOVI™ board:
*A 7V to 16V 500mA external power supply that powers MOVI™ through the Arduino board. The power consumption of both boards is just above what the USB port can provide. If you don’t have already one, this 9V adapter from Adafruit will work perfectly.

So could I use the 5V power supply, connect it to the 5v pin and still plug in a 9v Power supply in that barrel jack to power the [Movi Shield]?(MOVI - Audeme).

Thanks.

I think @Paul_B has some bias against the on board regulator. Unless I missed, I didn’t see the spec sheets I read required external heat sink for the specifications to hold, rather they quote ambient temperature. From my experience, you can go ahead with a single 9V supply. The supply will provide 5V through arduino’s 5V regulator and will also likely be directly sent to your MOVI shield via vin as it requires that much voltage. Do mind how you enclose your project and whether it has some way of passive cooling, enough size for heat to dissipate, and away from direct sun light and heat source.

Oh well, I’m out then. Forget I was here! :grin:

Really depends on the current draw. I powered a Duemilanove and 4 MAX7219s from 9V, it would overheat and shut down, cool off, restart, overheat, shutdown.
Switched to 7.5V supply and had no problems.
This video is USB powered, took it to work show off, with 9V for the barrel jack, had to switch to 7.5V the next day.

Ok. Thanks.

I have two powerful 12v fans that will be put into my enclosure (one is exhaust and the other bring fresh air in) so the cooling shouldn’t be too much of an issue.

Thanks for all your help.
I’m going to go ahead and try a 9v 5a power supply with a y-Cable splitter so I can power both my Arduino Mega’s.