Arduino Mini Pro 5v - how to power

  • By mistake I bought some time ago 10pcs of Arduino Mini Pro 5v (instead of 3.3v) and now I've got a problem how to give them power? It's better to use:

    • 2x1.5V AA batteries and use step up converter to get from 3.0v -> 5.0v

    • 4x1.5V AA batteries and use step down converter to get from 6.0v -> 5v

    Or maybe there is different possibility? I will be really happy if someone will be able to help me with this issue.

  • Hero Member

    You have two potential voltage inputs:

    • 7v+ @ Vin to the input of the onboard linear regulator
    • 5v @ VCC to the processor (and the output of the onboard regulator).

    The 7v+ figure is approximate, it depends on the onboard regulator and the current draw, but the APM generally does not have a Low Dropout Regulator so it needs a couple of volts of drop.

    You could use an external step down converter to drop 6V nominal to 5V for VCC pin - that could be a external low dropout regulator. There's not much point to a switching "buck" regulator - when dropping from 6V to 5V, the LDO linear regulator will probably be more efficient, cheaper, smaller, etc.

    Or you could use a switching "boost" or up converting regulator from the nominal 3V source to 5V for the VCC pin. Either can work.

    Either way, since you are going in through the VCC pin, you may want to unsolder the onboard linear regulator, to avoid it wasting power when fed from it's output.

  • Thanks for information. So as I understand I can use those element - New 1-5V to 5V 500mA DC-DC Boost Converter Step Up Power Module ( to convert 3.0v to 5.0v ?

  • Code Contributor

    @ddluk I run my 5v 16mhz at 3.3v.. Direcly off 2 AA batteries too (I think the reported voltage last I checked was 2.88v, Still works just fine. 🙂 (But I have flashed bootloader to disable brownout voltage)

  • @Damme

    Could you tell me how to flash this bootloader? It will be nice to use those 5.0v with 2AA batteries 🙂

  • Mod

    @Damme said:
    But I have flashed bootloader to disable brownout voltage

    Interesting, are you saying that you removed the boot loader and use an external programmer or do you use another bootloader (I must admit that I did not pay attention too much when the bootloader was discussed elsewhere on the forum)?

  • Hero Member

    I think he's talking about setting fuses, rather than the bootloader per se - but it's often done with the same tool (eg: AVRDUDE).

    The bootloader is code that runs in a protected portion of Flash memory. The fuses are a few extra bytes of low level processor configuration. Both are set using the same tools.

    You can google for programming ATMega328 fuses (and look in the datasheet for the bit values).

  • Hero Member

    Anybody have any thoughts about running the Pro Mini 5v or 3.3v on one of these:


  • Mod

    @Zeph interesting stuff. Will look that up as soon as I am home again...

  • Admin

    I've added an ISP programmer (used to program Arduino bootloader) in the "shop" now.

  • Hero Member

    @hek looks like you've ha enough of arduino slowdown you now propose a cubie 😉 A lipo would be a very good addition to the store too !

    I'm searching for a leaf wetness sensor... not a rain sensor, hard to find as it seems...

  • Admin

    Cubie has a bit more processing power than RPi. For the demading controllers 🙂

    @epierre said:

    leaf wetness sensor

    The only leaf wetness sensors I can find is super expensive. Like this:

    Can you (or someone else) recommend any lipo battery seller on ebay? I haven't got any buying experience just yet.

  • Hero Member

    @hek yes it looks like I've added one sensor to much on the raspi... (infact 10...)

    For the Lipo, no idea yet (not supercaps...), I was hoping this thread would propose something interresting...

    For the leaf wetness I'll try with the rain sensor but... I need some autonomous energy system for it will sleep outside...

  • Mod

    @hek @epierre What exactly is a 'leaf wetness sensor' and in what does your link differ from e.g. ?

  • Admin


    Probably just a calibration/quality thing. The technique/principle is probably the same.

  • Mod

    @hek OK thanks.
    Reading this I think there also is a very close relation to humidity sensor readings. Would be nice to see the readings of both next to each other!

  • Hero Member

    @Yveaux @hek I've forked to its own post:

    I'll try to add things following mysearches and experiments

  • Hero Member

    they have the same at (hardware cum software like mysensors, same radio different core) :

    The battery shield is a LiPo battery charger and voltage regulator combined into one. You can use it to power your Core with any 3.7V LiPo battery and charge it at the same time via the USB port. The shield is built around Microchip's MCP73871 battery charge management controller and TI's TPS61200 boost converter for up converting 3.7V to 5.0V.

    There are plenty of 3.7V lipo batteries on ...

  • Admin

    @epierre said:

    Moustache shaped LiPo charger. Hmm.. 😉

    The lipo-rider looks good, but there's mostly the older version on ebay. They seem to have switched JST-connector-version between their rider-revisions.

    It is still hard to recommend LiPo batteries from ebay without doing some tests on them. I wouldn't use any without protection as they might explode if you use/charge them wrong.

  • Hero Member

    @hek sadly I'm not expert at all on this to test them...

  • Because discussion is going to different direction than topic could any of you clarify what exactly I will need to power those 5.0v mini pro. I'd like to order parts to get them this month 🙂

  • Hero Member

    A tested and trustworthy Li-Ion battery supplier could be a good thing. I'm glad @hek is waiting to know something about a vendor before suggesting them, they do need to be vetted.

    From what I've read, there are a lot of cheap rebuilt ones out there. Some may just substantially exaggerate the capacity but do work OK, some won't last long. And of course, they are more dangerous than most of our components. You can't tell what you are getting from the outside and many vendors take advantage of that so there are a lot of fakes out there.

    A good source for info is the flashlight lover sites like

  • Hero Member

    @ddluk said:

    2x1.5V AA batteries and use step up converter to get from 3.0v -> 5.0v
    4x1.5V AA batteries and use step down converter to get from 6.0v -> 5v

    Let me try again on this one. The answer depends on what else you need to power (assuming that you feed Vcc without using the onboard regulator).. Like do you have any other 5V devices (eg: sensors, actuators), and/or any 3.3v devices (eg: sensors, radios).

    If you need regulated 3.3v,and you want to sleep to save battery, I'm becoming attracted to the idea of 3c 1.5v alkaline and MCP1700 linear regulator. When your duty cycle is low, the efficiency of the regulator under load for short periods becomes less important to battery life than the quiescent current of the regulator (and the sleep mode of the processor and other devices).

    As others have said, if all of your devices can handle the voltage range, using 2 or 3 batteries without a regulator becomes another option. The ATMega328P and other AVRs are remarkably tolerant of voltages (with appropriate brownout fuses if necessary), so it's more about the other devices.

    If you power the 5V APMs via the VCC pins, I would at least test the sleep mode power drain and be sure the unused backward-fed onboard regulator isn't drawing too much current and remove it if so.

  • Hero Member

    @Zeph said:

    Is there a componant including it ? I would have gone for an AMS1117 asproposed in the store ?

  • Hero Member

    @hek I'm sure the oustache will fit you perfectly 😉

    From Adafruit website I've extracted two LiPo batteries reference, maybe we could start this way ? would there be fakes of some reference ?
    PKCELL LP803860
    18650 3.7v 2200mAh samsung version

  • Hero Member

    I'm not aware of a standalone regulating module with the MCP1700, but have not looked extensively. The regulator itself is available from digikey etc or on ebay, in TO-92 or SOT-23 form factors.

    The MCP1702 also has good specs on quiescent current (tho not as good), and accepts higher input voltage.

    I don't recall all the places I've read about these, but they are used in some low power devices.

  • Hero Member

  • Admin


    Thanks. The RC community has worked with batteries for a long time. Guess they're experts 😉

  • Hero Member

    Let's clear something up. There are two battery technologies mentioned in this thread, and perhaps sometimes confused.

    Li-ion. (lithium ion) @korttoma pictured one of these early one, and another was linked a few message above. Typically cylindrical in 18650 or 14550 size tho others exist; the size matters since they fit in holders like AA. Some have protection circuits in little disc shaped PCBs at the end, some do not. Lots of fake "name brands" from chinese forums. Flashlight afictionados seems to know a lot about them.

    Li-Po (lithium polymer) These are usually rectangular and flat or flattish, and have wires to some little connector. Many sizes (since all you need is the right connector and enough space). Sometimes packed with multiple in parallel and/or in series for higher current or voltage. The rc model community seem to be the experts on these.

    Both have similar voltages, and similar chemistries, and similar energy density per volume. LiPo is a bit lighter so it has better energy densidty per weight, important for flying things. LiPo is also useful where rectangular fits better. Both need protection (internal or external) from excessive discharge (or excessive charge, and short circuits etc). You can get by with draining a NiMH or Lead Acid or NiCd battery to zero (tho it's not good for any of them), but don't do that with either Lithium type!

    I have Li-Ion in my flashlight, and LiPo in my micro-quadcopter.

    As far as I can tell, some of the messages above may be saying "LiPo" when referring to Li-ion or vice versa. So I wanted to get us on the same page.

  • Hero Member

    @Zeph said:

    Both need protection (internal or external) from excessive discharge (or excessive charge, and short circuits etc)

    That is where our new library to check battery level goes in, we could dream to have an internal mysensor security check of a LiPo battery ! they do so in 'copters

  • Hero Member

    @epierre said:

    Both need protection (internal or external) from excessive discharge (or excessive charge, and short circuits etc)
    That is where our new library to check battery level goes in, we could dream to have an internal mysensor security check of a LiPo battery ! they do so in 'copters

    I may pass on that. I'm not used to software glitches having quite so much potential impact, and I don't need to save every gram. But to each their own!

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