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Nettigo Air Monitor HECA 2

2 months ago 97
  • Description
  • Documents
  • BOM
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Description

HECA 2 - relative humidity air conditioning device for PM sensors

HECA 2 is more compact version of HECA with different enclosure.

In this design we used precise temperature and humidity sensor from Swiss company Sensirion: SHT30 (or SHT31/SHT35) connected via I²C. This sensor is equipped with programmable ALERT output. This output is connected to N-channel MOSFET and controls 5W heating resistor. Huge advantage of this design is ALERT logic which can be programmed via I²C and it's independent from main micro controller. In other words apart of sensor initialization it doesn't require any action from main micro controller.

HECA 2 vs HECA - Main changes

  • Form factor: The enlosure is now smaller and made of aluminium profile (TOPMET Smart16)
  • Placement: Entire device is now placed inside NAM 0.3
  • Heating element: 5W resistor instead of PTC heating element
  • Connection: 5 pin header instead of 4 pin cable and 2 wires.

Usage outside of NAM project

You may use HECA 2 as inline relative humidity conditioning device for other PM sensors or projects.

  • Connect SCL, SDA, 3V3, GND and high amperage 5V (up to 20V).
  • Circuitry supports heating element voltage from 5V to 20V. But you may need to change resistor value to keep it in 5W range. Although we recoment keeping it between 2.5W to 3.5W.
  • I²C address is set to 0x44 permanently. In this design address can not be changed. If you modify PCB before production and connect SHT30's ADDR line to 3V3 you will change addres to 0x45.

Project support

If you would like to support this project consider buying assembled module form Nettigo.eu or Nettigo.eu.

License

Documents

NAM HECA 2

PCB NAM HECA 2

BOM

ID Name Designator Footprint Quantity
1 FIDUCIAL 1,2 FIDUCIAL_1MM 2
2 100nF C1 0603 1
3 HDR-M-2.54_1x5 H1 HDR-M-2.54_1X5 1
4 AO3420 Q1 SOT-23-3_L2.9-W1.6-P1.90-LS2.8-BR 1
5 10KΩ R1,R2 0603 2
6 10KΩ R3 R0603 1
7 10Ω 5W R4 RES-5W-HECA 1
8 SHT30-DIS-F U1 DFN-8_L2.5-W2.5-P0.50-BL-EP 1

Attachments

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