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Author Topic: Power Options for Arduino Mega  (Read 3910 times)

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Offline jocatchTopic starter

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Power Options for Arduino Mega
« on: July 27, 2010, 11:01:22 AM »
While I am waiting for my Arduino Mega to come in the mail, I have started thinking about how I am going to power my robot. The Arduino website states the input voltage should be 7v or more. So I assume most people use 12v batteries then and 12 volt motors? How robust is the 5v on board regulator on the Mega card? One option I was thinking was using my 12v battery and a 7805 (I have lots of 7805s around). Is there a 5v input to the Mega card? Or should I just feed the Mega with 12v directly?

If people are using 6v batteries and motors, how are they getting around the 7v min requirement?

Thanks.

JC

Offline macdad-

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Re: Power Options for Arduino Mega
« Reply #1 on: July 27, 2010, 12:08:52 PM »
The Arduino website it recommends 7-12V as the unregulated safe input range for the Arduino's regulator. Here are the specs for the regulator:

Minimum input voltage: 6V
Absolute Maximum input voltage: 20V
Maximum output current: 800mA

More info here:
http://pdf1.alldatasheet.com/datasheet-pdf/view/12048/ONSEMI/MC33269D-5.0.html

It's voltage drop out is 1V, and since it regulates a 5V output, running it on four AA batteries at 6V won't last you long once their voltage drops below 6V. You could try using 9V batteries although you won't have much Amp Hours to work with.

You could also use 7.2V Lithium Poly batteries, although they are relatively hard to get and finding a charger for them is equally hard.

Since you already have a 12V battery with you, that would be your best course of action.

Hope this helps,
Nick(macdad-)

Offline jocatchTopic starter

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Re: Power Options for Arduino Mega
« Reply #2 on: July 27, 2010, 01:12:30 PM »
Thanks Nick for the info. I plan to be adding sonar and infarred senors and maybe a GPS someday. I need to calculate the current drain of all that along with the Mega itself. I may still feel more comfortable using one of my 7085s (maybe in addition to). My 12v battery is a very nice SLA type and although it does weigh almost 6 pounds, it should be able to supply the Mega for a long time. Of course, I need to get 12v motors that are powerfull enough to move the battery and frame, still have not decided on the motors yet. But I think I need between 90 - 120 RPM units.

JC

Offline macdad-

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Re: Power Options for Arduino Mega
« Reply #3 on: July 27, 2010, 01:32:16 PM »
If your planning to use a sonar unit, then you should put one of your 7805s to work, as sonar modules usually use quite alot of current, averaging about at half an amp. That is why I still favor the 7805s and their varieties as they can handle much more current than a surface-mount regulator and are easier to configure/setup. GPS and IR units you can use on the same regulator with the Mega as they typically use less than 100mA.

On the topic of motors, there is another guy talking about a robot he built for outdoor exploring using a couple of 12V drill motors:http://www.societyofrobots.com/robotforum/index.php?topic=11712.msg88561#msg88561



 


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