Help with power for arduino mega2560

Hi, I appreciate this is not specificaly a PIO query, but if anyone could help, I’d appreciate it.

I have two 12 volt lead acid batteries in series to power a stepper motor driver MA860H spec here

My query is this, can I use one of the 12V batteries to power a Mega2560 ? the connection from the battery goes to a USB converter/ connector, so 12v converted to 5v and a usb cable connects to the Mega2560.

The reason I’m asking is just in case there might be noise on the 12V line (from the stepper motor driver box), and this might affect the stability of the AVR chip. Unfortunately I don’t have access to an oscilloscope to monitor this.

Alternatively, I could use a separate 12V battery, but space is limited and I’d like to avoid another battery if possible.

It’s all at a remote location with no mains power.

thanks for thoughts on this.

To be honest, I don’t know!

However, you can take a feed from on of the 12v batteries to power the Mega via some form of step down to 5.5v absolute maximum voltage. Maybe adding a ferrite ring into the power lines, close to the Mega will help reduce noise. I’m no expert though, sorry.

One othr problem to be aware of, when the batteries start getting towards too low a voltage, th stepper may drag the voltage down too far for the Mega to run properly, and the BOD will reset it. (Brown out detector) – what state would that leave your project in if the Mega restarted while the stepper was running?

As for an oscilloscope, have you looked at the Espotek Labrador? It’s all I’ve got but it does the job. It’s not usable above 5V on the input lines though. Mine runs on Linux but it works on Windows too. You can read about it at EspoTek Labrador – Official EspoTek Online Store. Current price is $29. Mine was £24 when I bought it. In fact, I got two! Haven’t blown one yet.



Thanks for reply Norm, The inductor idea might work if there were spikes on the DC line. For an inductor with inductance L, the impedance is XL = 2 x Pi x f x L where f is frequency, so at zero frequency DC the impedance is zero which is what I’d need, with the impedance rising as the frequency of spikes rises.

If I sound like I might know what I’m talking about, don’t be fooled, it does seem to make sense though.

The bit I don’t know is if there were such spikes, do I need to remove them before they get to the Mega2560. I guess I might be better off asking in an electronics forum.


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Hi Paul,

I have DC power supplies/ wall warts which have inductors on the DC output wires. Both my old (16+ years) and new (2 months) Dell laptops have them. Also my 8 way network switch power line too. All are DC – I checked! Given your reply above, I’m wondering why now.

Anyway, good luck with the problem, sorry I was of no use. And if you can, give the Espotek oscilloscope a look see. I’m not involved other than as a satisfied customer.


yes the scope looks interesting Norm, I’ll probably get one to try.

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If you cannot apply DC power to the barrel jack, then skip my reply.

You can power the mega2560 with 7vdc (or more) from an external supply. A 12vdc battery can drive a 7808 or 7809 linear regulator to produce the correct power for the mega input. These regulators require 0.1uf caps on the input and output pins.