Soldering of External Battery

[espruino-discuss]

Posted at 2019-09-21 by user103487

Hi Guys,

I have pulled one of my puck.js out of the draw again recently and have tried to drive it with a 3.3v power source for prototyping. Not sure what I am going to do with it but I would prefer not to burn through my batteries while prototyping so I have soldered on some headers and tried driving it through GND and 3v pins but this board has had some abuse and I didn't know how to solder when I orginally got it and it seems I damaged the trace...

Anyway, my question is can I use D24 and D23 for power connection?
I recall that they were supposed to be for external battery connection but can't find any info about it.
e.g. which one is GND?

[espruino-discuss]

Posted at 2019-09-21 by Robin

Fri 2019.09.20

I opened up the info page from:

http://www.espruino.com/Puck.js

below heading 'Information' opened up the schematic:

https://github.com/espruino/EspruinoBoard/blob/master/Puck.js/pdf/puckjs_sch.pdf

The correlation seems to be P0.15 == D15 so for D23 and D24 might be the pins in the upper right of the chip pinout. A rollover of the image from the first link indicates those two pins are not 5V tolerant, so this implies I/O rather than power, and the schematic seems to confirm this.

p.14 seems to confirm also:

http://www.espruino.com/datasheets/nRF52832_PS_v1.0.pdf

The board layout didn't provide any important additional info:

https://github.com/espruino/EspruinoBoard/blob/master/Puck.js/pdf/puckjs_brd.pdf

It seems the two pad GND through hole near D11 and the 3V power near D7 are the best bet.

'it seems I damaged the trace'

Could there be an unintentional bridged solder connection?

Do you have an ohm meter to check for shorts- opens?

Any chance an image of the botched solder area could be uploaded for us to determine if traces were in fact damaged? Other than an extremely long heat contact time way over two seconds with a high wattage iron (above 22W), might damage the copper trace, or repeated attempts without a proper solder removal means (vacuum, solder wick). Otherwise, within those estimated ranges should be okay. A keen eye here might confirm or provide a glimmer of hope . . . .

[espruino-discuss]

Posted at 2019-09-21 by user103487

I had to remove the header.
I then soldered the trace back down, it seems I had previously melted/burnt it out... don't ask.
In the end I just soldered some jumper wires directly to 3v and gnd and it works fine.
I would still like to know how I would go about attaching a lipo battery connector and where that could best be achieved.

[espruino-discuss]

Posted at 2019-09-21 by user103487

Thanks Robin,

I had the same info, I was just looking for more.

The copper trace was about 3mm short of the pad when I took the header off, I thought I might catch it with solder but I underestimated my previous ineptitude... and didn't check.

[espruino-discuss]

Posted at 2019-09-21 by Robin

Sat 2019.09.21

'attaching a lipo battery connector'

If it wasn't understood from the (lower left) schematic, remember the need for a diode drop using LiPo.

See p.17 Sec. 6 of datasheet

[gfwilliams]

Posted at 2019-09-23 by @gfwilliams

D23/24 are just IO pins...

Luckily the big metal battery clip is all 3v, so if you need to attach a wire because something got broken you could solder on to one of the two 'lugs' where it attaches.

With LiPo, as @robin notes you'll need a diode to drop the voltage (since when fully charged, LiPos produce too much voltage). There's no place in particular that was made for adding one because of that.

However if you wanted to use an LR2032 rechargeable coin cell battery then there is space to add a diode on the PCB.

If you look at http://www.espruino.com/Puck.js#pinout you can see just above pin D27 there are 2 little solder pans. If you cut the PCB below them then it'll disconnect the 3v from the battery and you can solder a surface mount diode in there. ...but fitting a diode there is a pretty delicate soldering job so I'd only attempt that if you're feeling confident :)

One other thing is if you want to mess with Espruino without coin cells there's always http://www.espruino.com/Pixl.js that you can run off micro USB, or http://www.espruino.com/MDBT42Q which does have space to solder a LiPo connector as it's got a voltage regulator on it.

[espruino-discuss]

Posted at 2019-09-24 by user103487

Thanks Everyone! I'll look in to my options from there.