mBuino Battery

Just want to confirm before I buy a bunch of them, is the CR2032 the correct battery for the mBuino battery holder? That’s what’s shown on the KS page, but I wanted to make sure nothing changed prior to the rewards shipping.



Yes, the battery holder that comes with the kickstarter reward is the for a CR2032

Although I didn’t use it, I had https://www.sparkfun.com/products/783 these on hand - and found them easier to hand solder with pins than a flat pad.

Did you flatten out the pins? I’m assuming you didn’t drill out the board.

Yeah, I just flattened them out and it sat nicely. The coin cell holder that came with the mbuino has contacts that almost totally cover the boards pads. I guess cutting the contacts on an angle would also work - but I was in a hurry.

The battery holder that comes with the mBuino also solders easily. Just put some solder on the bottom of battery holder pad and some on the board solder pad. And then heat up die battery holder pad from the top side with the soldering iron. The two then mends neatly and looks very good.

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Yep. Did just that. Then I realized that because I wanted to mount the mBuino on a breadboard with the LEDs visible, I had to remove the battery holder. D’oh!

Looks like I need to order another mBuino for battery use, and use the one I have now as a breadboard device. Good thing they’re cheap. :slight_smile:

I’ve already soldered battery holders on two mBuino’s. No problems, just put a bit of solder on the individual connections first. After that, joining is easily done by just pushing the soldertip onto the holder connection placed on the tab.

I also added header pins to one of them, for breadboard use. No problem either, just make the pins a bit longer by pushing the black plastic bar a bit closer to the pin ends. By doing so the button-cell holder can stay at the bottom-side to allow for breadboard experiments with dual or battery only power supply.

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Is it possible to use LIR2032 rechargable litium cells with a max. voltage of 4V2?
According to sec. 8 (Limiting values) of the LPC11U2x datasheet
it shouldn’t be a problem for the uC. But what about the LEDs?

Btw, there seems to be no pad for the only high-drive output pin PIO0_7.
Is it needed for a LED?

The battery must be 3v

Thanks Gus

What about the 5V pad? According to the schematics this goes
to a BAT54C Schottky diode with a voltage drop of about 800mV @ 100mA
and to an AP2112K-2.2TRG1 LDO regulator with a voltage drop of about 50mV @ 100mA.
If we apply this overall 850mV voltage drop to the discharge curve of a LIR2032
we end up just a little bit below the discharge curve of a CR2032.
At least we are on the safe side if we go through the LDO. Any concern?

Furthermore, JST PH connectors of LiPo packs almost fit the 5V / GND pads/holes.
It should be possible to squeeze in a JST socket.

Maybe cou could officially support LiPos (switch to route battery pads to the regulator,
JST socket, LiPo charger) in a future mBuino release?
I understand that this is difficult if you have a 10$ policy for Outrageous Circuits.

@ HH - yes you can use 5v but I am not sure if you can plug both usb and feed 5v. Use either till you check the schematics please.

Welcome to the community.

That should be fine. There is a diode (D8, a BAT 54C) that ensures that power will be drawn from whichever is at a higher voltage, the USB VBus or the +5V input pin, you can’t feed power (beyond the diode leakage current) between the two so it should be safe to have them both connected.