Please note: Friday June 18 is a holiday celebrating Juneteenth, please allow extra time for your order to arrive and plan accordingly.
0

How to add an LiPo charger to QT Py?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

How to add an LiPo charger to QT Py?

by zKyd on Wed Mar 24, 2021 12:42 pm

We're working on a small device where the Feather footprint is too long, but the QT Py board fits in nicely.

We'd like to have a LiPo battery connected to the microcontroller, such that it can power the board as well as be recharged through the USB port on the board. The Feather line has this ability built-in, but QT Py does not.

What is the simplest option to charge an attached LiPo battery on a QT Py device? This USB charger appears to have the ability to recharge the battery, but we'd like to avoid manually moving JST plugs on the battery. I'm also unsure if we attached this device to the respective pinouts on the QT Py, if that'd allow the attached battery to recharge.
https://www.adafruit.com/product/1304

zKyd
 
Posts: 4
Joined: Sat Aug 08, 2020 6:59 pm

Re: How to add an LiPo charger to QT Py?

by dastels on Wed Mar 24, 2021 2:38 pm

The QtPy isn't designed for a battery. It assumes a 5v supply. I would suggest a Powerboost 500C or 1000C. That would generate 5v from the LiPo battery as well as let you connect USB to charge the battery (while powering the QtPy). Connect the 5v output from the powerboost to the QtPy's 5v pin as per:
This is 5v out from the USB port. You can also use this as a voltage input but you must have some sort of diode (schottky, signal, power, really anything) between your external power source and this pin with anode to battery, cathode to 5V pin. Note that you cannot power the USB port by supplying 5V to this pin: there is a protection diode that prevents the 5V from reaching the USB connector. This is to protect host computer USB ports, etc. You can draw 1A peak through the diode, but we recommend keeping it lower than that, about 500mA
(from https://learn.adafruit.com/adafruit-qt-py/pinouts.

The drawbacks would be that there's another board involved, and you'd need to use its USB connection to change the battery (not the QTPy's).

Dave

dastels
 
Posts: 6489
Joined: Tue Oct 20, 2015 3:22 pm

Re: How to add an LiPo charger to QT Py?

by CapArcona on Tue Mar 30, 2021 6:30 pm

dastels wrote:The QtPy isn't designed for a battery. It assumes a 5v supply. I would suggest a Powerboost 500C or 1000C. That would generate 5v from the LiPo battery as well as let you connect USB to charge the battery (while powering the QtPy). Connect the 5v output from the powerboost to the QtPy's 5v pin as per:
This is 5v out from the USB port. You can also use this as a voltage input but you must have some sort of diode (schottky, signal, power, really anything) between your external power source and this pin with anode to battery, cathode to 5V pin. Note that you cannot power the USB port by supplying 5V to this pin: there is a protection diode that prevents the 5V from reaching the USB connector. This is to protect host computer USB ports, etc. You can draw 1A peak through the diode, but we recommend keeping it lower than that, about 500mA
(from https://learn.adafruit.com/adafruit-qt-py/pinouts.

The drawbacks would be that there's another board involved, and you'd need to use its USB connection to change the battery (not the QTPy's).

Dave


I'm doing something similar. Would this MiniBoost do the trick? A PowerBoost500C is too large, and has many features I don't need.

CapArcona
 
Posts: 15
Joined: Wed Mar 03, 2021 4:13 pm

Re: How to add an LiPo charger to QT Py?

by dastels on Tue Mar 30, 2021 7:07 pm

Yes, that will convert 2-5v to 5v. If you are using it with a LiPo you'll need a connector (these are available as a breakout https://www.adafruit.com/product/1862 and remove it to charge.

Dave

dastels
 
Posts: 6489
Joined: Tue Oct 20, 2015 3:22 pm

Re: How to add an LiPo charger to QT Py?

by CapArcona on Wed Mar 31, 2021 1:23 am

dastels wrote:Yes, that will convert 2-5v to 5v. If you are using it with a LiPo you'll need a connector (these are available as a breakout https://www.adafruit.com/product/1862 and remove it to charge.

Dave


Is 0.1a enough to power the board and a 128x32 OLED screen? it seems awful low but my small electronics expertise is solely limited to RC planes.

CapArcona
 
Posts: 15
Joined: Wed Mar 03, 2021 4:13 pm

Re: How to add an LiPo charger to QT Py?

by dastels on Wed Mar 31, 2021 10:41 am

On average the display uses 20mA according to the guide: https://learn.adafruit.com/monochrome-oled-breakouts. That leaves ~80mA for the board. Which is plenty (the SAMD21 datasheets states 30-40mA). Any attached sensors or such will have their own requirements.

Dave

dastels
 
Posts: 6489
Joined: Tue Oct 20, 2015 3:22 pm

Re: How to add an LiPo charger to QT Py?

by CapArcona on Wed Mar 31, 2021 2:40 pm

Perfect, thanks Dastels!

CapArcona
 
Posts: 15
Joined: Wed Mar 03, 2021 4:13 pm

Please be positive and constructive with your questions and comments.