Mini-BT-Pcb-328P

This small PCB (55×35) is born to be a general purpose solution for building any kind of compact wireless battery powered sensor or actuator based on MySensors, an ATMega328P (Arduino) and a RFM69 or NRF24 radio module.

The board has a dedicated footprint (SW3) for a reed switch, while other type of sensors and actuators can be connected with the MYSX connector v.2.6

The board can be powered in different ways:

  • 2 x AAA batteries (Rechargeable or Alkaline)
  • 1 x AAA battery (BT2), closing the jumper J4 and shorting the CE pin and the ON pin on jumper J3 and the 3.3V pin and the Vcc pin on jumper JP1
  • 1 x CR2032 battery
  • At 5V through the micro USB connector
  • At any DC voltage between 5V and 12V, shorting the jumper JP3 and connecting your power source to the Vin and GND pin of the MYSX connector

The board supports different radio modules:

  • RFM69 radio module
  • NRF24 radio module THT version
  • NRF24 radio module SMD version

The flexibility in the battery type usage is possible, among to other things, thanks to this boost converter that increase the voltage to 3.3V.

The schematic and the entire Kicad project are available for download in the dedicated d-diot github repository. In the repository you can find the gerber files of the PCB, so you can easily get 10 boards with about 5€ using an online PCB manufacturer like JLCPCB or PCB way.

Click the button below to download the complete set (zip) of gerber files necessary for the manufacturing of the board v.1.0.

Download Gerber Mini-BT-Pcb-328P v.1.0

This is how the board looks:

Below the schematics ( pdf format).

Mini-BT-Pcb-328P Schematics

Use the interactive BOM tool to see where to place each component

Visit the dedicated topic in the forum if you need to know more.

In the board v.2.0 a solder jumper (JP5) has been added. When shorted, this jumper connects the plus terminal of the batteries to the analog pin A7 of the MCU, so that the battery level can be estimated also if the MCU is powered through the boost converter.

Click the button below to download the complete set (zip) of gerber files necessary for the manufacturing of the board v.1.0.

Download Gerber Mini-BT-Pcb-328P v.2.0

This is how the board looks:

Below the schematics ( pdf format).

Mini-BT-Pcb-328P v.2.0 Schematics

Use the interactive BOM tool to see where to place each component

Visit the dedicated topic in the forum if you need to know more.

The main features of the pcb are:

  • Small dimensions: 55 x 35 mm
  • Multiple power options: 2 x AAA batteries or 1xAAA battery (Rechargeable or Alkaline), 1 x CR2032 battery, standard cellphone charger at 5V through the micro USB port or through Vin and GND pin of the MYSX connector
  • Reverse polarity protection (Mosfet Q1) to prevent damages in case of wrong batteries insertion.
  • Boost converter (ME2188C33) to increase the battery voltage to 3.3V when necessary
  • LEDs for radio traffic and low batteries signaling. All configurable in the firmware.
  • Multiple radio module supported: NRF24L01 (SMD and THT) and RFM69.
  • Footprint for a reed switch
  • MYSX connector v.2.6 that integrates the pins for FTDI and ICSP
  • Support for ATSHA204 chip (security and signing)
  • Mounting hole for a M2.5 screw
References Value Footprint Quantity
C5 22uF-Tantalum CAPPC3528X210N 1
C12 47uF CP_Elec_5x5.4 1
C1 100uF CP_Elec_6.3×5.4 1
C4- C7- C8- C9- C10- C11 0.1uF C_0805_2012Metric 6
C3- C6 10uF C_0805_2012Metric 2
C2 100uF-Tantalum TAJD107K016RNJV 1
R2- R3- R5- R9 10K R_0805_2012Metric 4
R6- R7- R8- R10 330 R_0805_2012Metric 4
R1- R4 20K R_0805_2012Metric 2
L1 22uH L_6.3×6.3_H3 1
D3- D5 Y-LED LED_0805_2012Metric 2
D2 R-LED LED_0805_2012Metric 1
D4 G-LED LED_0805_2012Metric 1
D1 SS14 SS14 1
U5 NRF24L01 NRF24L01 1
U6 NRF24L01 NRF24L01-SMD 1
U7 RFM69HW RFM69HW_SMD_Handsoldering 1
U3 AMS1117-3.3 SOT-223-3_TabPin2 1
U1 ME2188C33 SOT-23-5 1
U2 ATSHA204A SOT-23_Handsoldering 1
U4 ATmega328P-AU TQFP-32_7x7mm_P0.8mm 1
SW3 SW_Reed Reed-MKA-14103 1
SW2 Reset SW_1437566-3 1
BT2- BT3 AAA Cell AAA-Keystone-55 2
BT1 CR2032 BatteryHolder_Keystone_1058_1x2032 1
JP1 Boost PinHeader_1x03_P2.54mm_Vertical_SMD_Pin1Left 1
Q1 FDN338P SSOT-3 1
Q2 FDN337N SSOT-3 1
J5 ANT PinHeader_1x01_P2.54mm_Vertical 1
J1 Analog IN PinHeader_1x02_P2.54mm_Vertical_SMD_Pin1Left 1
J3 Booster CE PinHeader_2x03_P2.54mm_Vertical_SMD 1
J2 USB_B_Micro USB_Micro-B_Molex-105017-0001 1
P1 MYSX_2.6 PinHeader_2x11_P2.54mm_Vertical_SMD 1

The Mini-BT-Pcb-328P-firmware is available as a PlatformIO poroject in the d-diot github repo. For the moment the firmware supports the basic operations (like battery level reporting, external power detection, booster activation, signaling led, etc…) and the reed switch but other functionalities will be added in the future.

Follow the firmware upload guide to know how to flash your board with PlatformIO directly from your d-diot hub.

The configuration of the firmware is in the following files:

For each parameter, see the comments in the files.

Visit the dedicated topic forum if you need to know more.

  • hardware/pcb/mysensors/mini-bt-pcb-328p.txt
  • Last modified: 2020/02/23 17:11
  • by franzunix