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Mask Moisture Meter

A simple device that measures the moisture of face masks

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The moisture meter uses a coin cell and a 555 timer to measure the resistance of your mask. It blinks and beeps when the mask is wet. The project on github (https://github.com/RickP/MaskMoistureMeter) contains all files needed build your own.

This device uses a simple 555 timer and some passive components to measure the resistance of cloth. No programming is needed. All components can be ordered from the major distributors.

If the mask is dry, it lights up a green LED. If the mask is moist it blinks a red LED and also beeps with a piezo buzzer. The faster is blinks and the higher the beepers pitch the more moisture is in your mask.

Replace and/or wash moist masks immediately as wearing a wet mask is dangerous to your health.

The electronics was designed in KiCad (design files included) and has all information (LCSC part numbers) to order it assembled with JLCPCBs free SMT assembly service.

  • 1 × TLC555CDR 2V timer IC in SOIC-8 package
  • 1 × Keystone 1060 Battery holder
  • 1 × Case 3D-printable
  • 1 × Murata PKMCS0909E4000-R1 Buzzer (optional)
  • 1 × C&K KSC341GLFS 5.1x5.1mm SMD push button

View all 11 components

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  • 1
    PCB fabrication

    Ready to use gerbers files are included in the github repo under 'fabrication' 

    - 2 layers FR4
    - EIG finish recommended so the sensor area doesn't oxidize
    - Board thickness 1mm - otherwise it won't fit the included case

  • 2
    Assembly

    Parts

    BT1: Battery holder for a CR2032 coin cell. Alternative to LCSC part: Keystone 1060.

    BZ1: The buzzer. Murata PKMCS0909E4000-R1 - can be left out for LED indication only.

    C1 and C2: 100nf 0603 capacitor. Use any one with at least 5% tolerance and 6.3V voltage rating.

    D1 and D2: 0805 LED in green (D1) and red (D2). Use LEDs with a forward voltage of under 2.8V.

    R1 and R2: 0603 resistor with about 150 ohm. Adjust to tune the brightness of your LEDs.

    R3: 0603 resistor with 1k.

    SW1: 5.1x5.1mm SMD push button with gullwing pins and a height of 3 to 3.5mm. Alternatives to the LCSC part: Würth 430451035836 or C&K KSC341GLFS

    U1: 555 timer IC in 8-SOIC package that works at 2V. You can use: TLC555CDR, TLC555IDR, TLC555QDR or TLC555CD

    Everything can be soldered by hand but a stencil and reflow equipment makes it way easier.

  • 3
    Case

    A 3D model for the case is included in the github repo under 'case'

    Print in PLA, ABS or PETG without supports. 0.1mm layer height recommended.

    The board just snaps in, no tools needed.

View all 3 instructions

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