Sensebender Micro

The MySensors Sensebender Micro is a tiny Arduino compatible board stackable with a Nordic NRF24L01+ transceiver module. The Micro has been designed for extended battery life; e.g. it operates directly at the battery voltage without the need for power regulators for low power consumption. As it has been designed to sleep most of the time, the operating frequency (8Mhz vs 1Mhz) is not that big a factor on battery consumption, hence the Micro is running at 8Mhz as default to facilitate the easiest adoption of sketches. Even in its small form factor it's packed with great features such as temperature and humidity sensor, 64k extra flash memory and a hardware module for secure message signing and verification.

Need more? Expand the functionality by attaching additional breakout sensors to the five digital GPIOs, two analog inputs or the I2C interface.

The board has been preloaded with a sketch reporting temperature and humidity levels every minute.

Technical Specification

  • Very small footprint, 30 mm x 17.5 mm (1.18in x 0.69 in). Making it almost same size as the NRF24 module.
  • Arduino IDE 1.5.x & 1.6.x compatible.
  • Si7021 integrated humidity / temperature sensor.
  • 64kb SPI flash / e2prom onboard. Useful for over-the-air firmware updates. Also possible to use memory for a local sensor data cache.
  • ATSHA204A on board (connected to A3). Used for HMAC-SHA256 message authentication support.
  • Runs directly off 2x1.5V batteries (AA or AAA), without power converters.
  • Socket* for connecting the radio module on top.
  • Pin-headers* for D3-D7 on one side, and SDA/SCL + A0/A1 and power on the other side.
  • FTDI header similar to Arduino Pro Mini.
  • Standard Atmel programming ISCP header.
  • Pads for mounting a 32Khz crystal (when timing is crucial).
  • Status LED (on A2).
  • Factory programmed with DualOptiBoot bootloader.

*) You have to solder the radio socket, and pin-headers yourself if you need them mounted. Note: The actual NRF24L01+ module is sold separately.

Available pins

  • Powersupply (1.8 -> 3.5V)
  • SDA / SCL (I2C bus)
  • A0 / A1
  • D3 / D4 / D5 / D6 / D7
  • 6 pin ISP port
  • 8 pin standard NRF24L01+ connector layout
  • FTDI header for serial

Wiring Things Up

NOTE! Maximum allowed supply voltage is 3.5V, anything above this WILL fry both Si7021, flash and NRF24 radio module. There is NO voltage regulator on board (To keep supply current down to a minimum)

Available Pins

This picture shows all the available pins on the Micro board. Click on the image to enlarge it. The ISP connector exposes MISO, MOSI, SCK and RST.


Connecting Battery

The board has been designed to operate at maximum 3V (2x1.5V batteries). Make sure not to overfeed it or reverse the polarity. This would permanently kill it. Connect:
GND to minus (-) often marked with a black wire.
VCC to plus (+) often marked with a red wire.


Connecting FTDI Programmer

To upload a new sketch to your Micro board use a FTDI programmer. Remember to set it a 3v3 output using the jumper setting on the programmer.

Setting up Arduino IDE for Sensebender

Connecting ISP Programmer

Make sure the red-dotted ISP wire goes into ground on the board. Disable power feeding on 5V ISP programmers (remove jumper) and power up the board on VCC/GND from a 3V power source.


Mounting Radio

The radio can be soldered directly onto the board or in a socket.

Example Sketch

This example reports humidity and temperature levels to the controller every minute. To save battery it sleeps MCU and radio between sends.

If you connect A0 -> GND during power-up it will go into a self-test mode (reports status on serial output).

/mysensors/SensebenderMicro/Arduino/SensebenderMicro/SensebenderMicro.ino
Last updated by tbowmo, 23 Jun 2017, "Merge pull request #10 from mysensors/tbowmo-patch-1"

*Unable to fetch code from github*

Images

Design Files

NameSize# Downloads
MySensorMicro.brd183.63 kB1761
MySensorMicro.pdf23.82 kB3090
MySensorMicro.sch219.74 kB1750
Sensor.lbr33.06 kB1214
CHANGES.txt3.28 kB767
COPYRIGHT.txt416 B661
PRODUCT.txt108 B936
cern_ohl_v_1_2_howto.pdf55.06 kB1374

Bill of Material

QtyValueDevicePackagePartsDescriptionMFMPN
1LED-0402LED-0402D1VishayVLMO1500-GS08
0NMM05NO_SILK1X05_NO_SILKJP4Not mounted
0NMM06NO_SILK_FEMALE_PTH1X06_NO_SILKJP2, JP5Not mounted
5100nCAP-0402C0402C1, C2, C4, C5, C6Ceramic Capacitors
110kR-0402R0402R3
032768hzCRYSTAL-3060100552P-L3.2XW1.5MMQ1Not mounted
1330R-0402R0402R4
24k7R-0402R0402R1, R2
256kR-0402R0402R5, R6
14u7CAP-0603C0603C3Ceramic Capacitors
1AT25DF512C-SSHN-BAT25DF512C-SSHN-BSO-08IC2Flash 512K, 1.65V, 85Mhz Serial FlashAdestoAT25DF512C-SSHN-B
1ATSHA204AATSHA204ASOT23IC4AtmelATSHA204A-STUCZ-T
0NMAVR-ISP-6VERTAVR-ISP-6JP3Not mounted
1MEGA328P-AUMEGA48/88/168-AUTQFP32-08IC1AtmelATMEGA328P-AU
0NMPINHD-2X42X04JP1Not mounted
1SI7021SI7021DFN6IC3Silicon LabsSi7021-A20-GM1

Shopping Guide

3V AA Battery holder
For powering 3.3V Arduino.
6 available - $6.41   Buy
Stock unknown   Buy
FTDI USB to TTL Serial Adapter
For the Pro Minis you'll need one of these to program the module from a PC or MAC. Handles both 3.3V and 5V!
3969 available - $6.95   Buy
Stock unknown   Buy
Sensebender Micro
MySensors Sensebender Micro is a compact Arduino compatible board that is stackable with the NRF24L01+ radio. The module is designed for battery powered operation using standard 1.5V batteries and includes built-in temperature and humidity sensing with hardware security.
> More Info
In stock - $14   Buy

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