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Open source feather IMU piggy back
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Open source feather IMU piggy back

by jps2000 on Wed Aug 14, 2019 12:54 am

top view.png
PCB XDOF + TOF
top view.png (77.45 KiB) Viewed 63 times
https://github.com/jps2000/XDOF-TOF-feather-nugget
Feather nugget (piggyback PCB) with BNO080/BNO055 IMU BMP388 Baro and VL53L1X tof sensor

Small PCB that fits to feather interface. Tested with nrf52832 BLE4.2 Features

9DOF IMU BNO080 or BNO055
BMP388 Sensor for altitude measurements
TOF sensor VL53L1X up to 4 meters
1 neopixel status LED
ON/ OFF toggle button for battery use; USB auto on, shutdown from controller
Board fits inside the feather footprint

Open source hardware, producers and suggestions welcome

feather nrf52832: To achieve lowest battery current in off it is recommendend to remove the 100k pullup on EN (R5) and to replace the MBR120 shottky diode (D5) by a SI diode (1N4148).

jps2000
 
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Re: Open source feather IMU piggy back

by adafruit_support_mike on Thu Aug 15, 2019 2:46 am

Nicely done, thanks for posting the specs and the URL.


As an aside, replacing the MBR120 with a 1N4148 will cost about 400mV of headroom on the LiPo. The voltage on BAT will be near 3.0V while the LiPo voltage is in the nominal 3.7V range, and will be below 2.5V by the time the LiPo is mostly discharged.

I don't think that will cause any problems for most of the microcontrollers in the Feather line.. I think they all operate down to 1.8V.. but you might want to test the idea with a LiPo discharged to about 3.5V.

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Re: Open source feather IMU piggy back

by jps2000 on Thu Aug 15, 2019 4:02 am

Hi Mike
Thanks
However, the MBR diode is in series just to the 5V USB voltage so 0.7V loss there does not matter at all.
> 4V is no problem for the 3V3 LDO
Also the charger voltage/current does not pass this diode and hence does not influence charging behavior

Only thing to consider is that dissipated power is higher than using a Schottky.
But with " normal" currents this should be no problem. One may use a higher current rated SI diode instead.

See also this:
https://github.com/adafruit/Adafruit-nR ... B/issues/4

jps2000
 
Posts: 449
Joined: Fri Jun 02, 2017 4:12 pm

Please be positive and constructive with your questions and comments.