Integral Design

People who work in technology often spend many hours at the computer, which can make it difficult to maintain good posture.  I’ve been advised by a physical therapist to keep my chest high with my head and neck upright.  The problem is that fatigue tends to make me slouch. Then my neck is out of alignment, leading to some unpleasant grinding of vertibrae and tension in the shoulders.

The .NET Gadgeteer device in this example uses the Seeed accelerometer module, which can be calibrated with a single function to set the base position that should be maintained.  I use a relay module, also from Seeed Studio, to activate a beeper when the Z axis of my posture varies too far from the calibrated normal.

The accelerometer is similar to the sensor in a cell phone that detects whether the phone is in the horizontal or vertical orientation.  The methods that the Seeed module supports are more than adequate for this application.  There is a method to calibrate the position from which variation is measured.  Monitoring the Z axis of the variation is sufficient to detect the kind of slouching I’m trying to avoid.  For this prototype I simply attached the accelerometer to my sweater with a safety pin, as shown in the following photo.

Accelerometer on the Slouch

The rest of the hardware is shown in the following illustration. Clearly, it would be better to use a transistor or smaller relay and omit the display monitor if the user is going to take the device to work or travel with it.  The Display T35 module by GHI Electronics was useful while I was watching the output to determine what needed to be monitored to keep me sitting up straight.

.NET Gadgeteer Posture Regulator Hardware

The relay module from Seeed Studio includes four relays on a .NET Gadgeteer printed circuit board.  It provides three connection screws for each relay.  The connectors are labled 1NO, 1COM, 1NC etc.  NO is an abbreviation for normally open and NC for normally closed.  The common line is used in both kinds of circuits.  So, in this example, I used a normally-open circuit with a beeper and battery.  To close the cicuit, simply set the relay member to true.  The following code block includes a conditional statement that closes the circuit if the Z axis is less than 1.0, and the beeper prompts me to sit up straight.

    if (acceleration.Z < 1)
    {
        display.SimpleGraphics.DisplayText("Leaning forward",
            Resources.GetFont(Resources.FontResources.NinaB), GT.Color.Red, 25, 25);
        relays.Relay1 = true;
    }
    else
    {
        relays.Relay1 = false;
    }

Here’s another picture of the beeper circuit with the relay module.

Beeper Circuit with Relay

The following code block shows the complete Program.cs file that implements the application.

using System;
using Microsoft.SPOT;

using GT = Gadgeteer;
using Gadgeteer.Modules.Seeed;
using Gadgeteer.Modules.GHIElectronics;

namespace PostureAccelerometer
{
    public partial class Program
    {
        void ProgramStarted()
        {
            button.ButtonPressed += new Button.ButtonEventHandler(button_ButtonPressed);
            button1.ButtonPressed += new Button.ButtonEventHandler(button1_ButtonPressed);
            accelerometer.ContinuousMeasurementInterval = new TimeSpan(0, 0, 0, 0, 200);
            accelerometer.MeasurementComplete +=
                new Accelerometer.MeasurementCompleteEventHandler(accelerometer_MeasurementComplete);
            Debug.Print("Program Started");
        }

        void button_ButtonPressed(Button sender, Button.ButtonState state)
        {
            if (button.IsLedOn)
            {
                accelerometer.StopContinuousMeasurements();
                button.TurnLEDOff();
            }
            else
            {
                accelerometer.StartContinuousMeasurements();
                button.TurnLEDOn();
            }
        }

        void accelerometer_MeasurementComplete(Accelerometer sender, Accelerometer.Acceleration acceleration)
        {
            display.SimpleGraphics.Clear();

            if (acceleration.Z < 1)
            {
                display.SimpleGraphics.DisplayText("Leaning forward",
                    Resources.GetFont(Resources.FontResources.NinaB), GT.Color.Red, 25, 25);
                relays.Relay1 = true;
            }
            else
            {
                relays.Relay1 = false;
            }

            display.SimpleGraphics.DisplayText("X: " + acceleration.X.ToString(),
                Resources.GetFont(Resources.FontResources.NinaB), GT.Color.Green, 20, 50);
            display.SimpleGraphics.DisplayText("Y: " + acceleration.Y.ToString(),
                Resources.GetFont(Resources.FontResources.NinaB), GT.Color.Green, 20, 75);
            display.SimpleGraphics.DisplayText("Z: " + acceleration.Z.ToString(),
                Resources.GetFont(Resources.FontResources.NinaB), GT.Color.Green, 20, 100);
        }

        void button1_ButtonPressed(Button sender, Button.ButtonState state)
        {
            accelerometer.Calibrate();
        }
    }
}

There is one more factor in sitting posture that needs to be correct to ease the strain on the spine and neck: the knees should be lower than the hips.  This is not difficult to maintain if the chest and neck position are correct.

There is now another implementation of this device that uses a LED alert instead of the buzzer.  See Posture Regulator with LED Alert – Silent.