Connecting Boron in waterproof enclosure to USB power


#1

I have a polycase wc-20f waterproof enclosure for a boron mounted on a gikfun mini solder-able breadboard. I also have a PG7 cable gland and a USB power cable (3.5mm) with the micro end cut off in order to pass it through the gland. My question is whether I can connect the 5V power wire from the USB cable to LI+? Boron tech specs suggest a tolerance for max voltage of 6.5 but I’d like to ask for suggestions here.


#2

Why the LI+ pin for a non-battery? I think Vusb would be a better option to connect a 5V non-battery power source to. But, then again, you didn’t state what’s on the “A”-side of the USB cable. A battery? A PC? A standard USB wall charger?

But I just looked at the datasheet again, for the LI+, it states only up to 4.2V:


#3

You should connect your power supply to VUSB and GND.

When powering with 5V to VUSB you should not use the actual micro USB connector (such as to monitor serial) unless you use a data-only cable that does not have the power line connected, as VUSB and the USB connector are directly connected to each other and the two power supplies would conflict with each other.


#4

Thank you both. My only power source will be a USB charger for a car/truck that should deliver a steady 5V. We’re just prototyping so no dashboard harness yet. I’ll post a pic when we’re installed.


#5

Quick question, I tried to power the Boron (wired with USB cable attached to VUSB and GND) from an MI.com 10000mAh power bank. It worked fine for about 5 minutes then the power bank turned off. I could turn it back on but a few minutes later it always turned off. Is there something about only using 2 of the 4 USB wires and continuously powering the Boron that is different enough to matter to a portable device like the power bank?


#6

The reason is most likely that the power bank goes into power-safe mode since the constant current draw is too low for it to register actual demand.
That’s a common issue with powerbanks and low power loads.


#7

Instead of cable gland and all that you may want to try using a wireless charging coil (like those used for cell phones). You can buy them very cheap for phone retrofits. Then lay the closed case with your boron onto a charging pad and you’re good to go, unless you’re using tons of power…


#8

Thank you both for the posts. What I was trying to do was take the Boron to a demo and show it in a working state without having to plug in a wall adapter. I wonder if there is a 3rd party “dumb” and equally portable power bank that would fit this use case?


#9

How large is your enclosure ?
You might be able to fit a 5aH, 8aH, or a 10aH Li-Po inside for your demo.


#10

https://www.polycase.com/ml-22f-1508 with PG-7 glands. The Boron just fits. :slight_smile: Here’s a pic of a partially assembled device. USB will come through the bottom gland. DS18B20 probes on either side.
boron_sc1


#11

Poor antenna :rofl:


#12

Work in progress. :slight_smile: