Introduction: IOT123 - ASSIMILATE SENSOR: MAX9812

About: The tension between novelty and familiarity...

Microphone Amplifier Sound MIC 3.3V / 5V Fixed Gain 20dB.

This build is based on the I2C MAX9812 BRICK.

If you need adjustable gain, I recommend swapping this sensor out for the MAX4466.

ASSIMILATE SENSORS are environment sensors that have an added hardware and software abstraction layer, making it possible for completely new types to be added to a ASSIMILATE SENSOR HUB and the readings be pumped to a MQTT server without added coding.

This ASSIMILATE SENSOR dumps 3 properties:

  • audMin (0-1023) - lowest value inside the 50ms (20Hz) sample window
  • audMax (0-1023) - highest value inside the 50ms (20Hz) sample window
  • audDiff (0-50) - a value derived from the difference of aMin and aMax

Step 1: Materials and Tools

This is the I2C MAX9812 BRICKBill of Material and Sourcing list.

  1. 3D Printed parts (3)
  2. CJMCU-9812 sensor (1)
  3. ATTINY85 20PU (1)
  4. 1" Double sided protoboard (1)
  5. Male Header 90º (3P, 3P)
  6. Male Header (2P, 2P)
  7. Jumper Shunt (1)
  8. Hookup wire (~7)
  9. Solder and Iron (1)
  10. Strong Cyanoachrylate Adhesive (1)
  11. 4G x 20mm self tapping screw (1)
  12. Hot Glue Gun (1)
  13. Craft Knife (1)

Step 2: Assembly

Follow the build instructions on IOT123 - I2C MAX9812 BRICK. Leave the CJMCU-9812 sensor detached from the circuit.

  1. Remove the 3P male header from the CJMCU-9812.
  2. On the rear of the CJMCU-9812, insert a yellow wire into "OUT" and solder.
  3. On the rear of the CJMCU-9812, insert a black wire into "GND" and solder.
  4. On the rear of the CJMCU-9812, insert a red wire into "VCC" and solder.
  5. Insert the 3D printed bracket to the CJMCU-9812 board from the top, bending the mic to the side if needed.
  6. Add a thin layer (~0.6mm) of hot glue to the extremities of the bracket. Let it cool.
  7. Trim solid glue with craft knife until snug fit in 3D printed lid.Insert the CJMCU-9812 and bracket into the 3D printed lid, bending slightly so that it falls in behind the BRICK in the base when assembled.
  8. On the rear of the BRICK, insert the yellow wire into YELLOW1 and solder.
  9. On the rear of the BRICK, insert the black wire into BLACK1 and solder.
  10. On the rear of the BRICK, insert the red wire into RED1 and solder.
  11. Bend the Jumper pins on the BRICK so that they clear the base when inserted.
  12. Insert the BRICK into the 3D Printed base grooves, with the 90 pins lining up with the voids.
  13. Turn over and press top of brick onto hard surface. If the top of the BRICK and the base are not aligned, remove the BRICK and clean up any filament that may be stopping the alignment and retry.
  14. When level, fasten the screw into the lower hole attaching the BRICK to the base.
  15. Tuck the wires into the base on the side of the solder to the BRICK.
  16. Put a dob of Cyanoachrylate on the lower tabs of the lid.
  17. Assemble the lid with the base aligning the tabs on the lid with the holes on the base.

Other than being a slight key for the bond the holes are used to gently press a thin tool in if needing to break the bond for maintenance.

Step 3: Testing

The testing (at this stage) can be the same as the underlying BRICK.

Just connect the jumper wires to the same pins on the underside of the ASSIMILATE SENSOR.

Step 4: Next Steps

There is enough code and circuit description for you to start your own ASSIMILATE SENSOR NETWORK.

Or you can check back here for more sensors and a MQTT Hub in the coming weeks.

Check out these related builds.