jeffkwoh / wheelchair_weighing_scale

Code for running a wheelchair weighing scale shared by multiple users

Wheelchair Weighing Scale

Motivation

A child's weight is an important indicator of their health. Especially moreso for children suffering from disabilities, their weight is important in determining the dosage of medication and monitoring their growth.

Taking the weight of those who are wheelchair bound can be extremely tedious for both the patient and the healthcare professional. The child must be hoisted off the wheelchair carefully, have the wheelchair's weight taken, in order to derive his weight.

This process introduces 3 complications:

1. The child may be injured if not hoisted with care
2. Being hoisted off is allegedly an unpleasant experience, creating a negative association with having one's weight taken
3. The healthcare professional may be injured if he cannot handle the child's weight

As such we aim to create a weighing scale which gives a more positive experience to the child.

This is achieved by building a weighing scale that is able to measure the child's weight while he's on the wheelchair after one calibration

Components

The system comprises of a Raspberry Pi, which acts as a central processor. It is connected to the following:

1. HX711 (provides weight readings via GPIO)
   • Load cells
2. Arduino (provides NFC readings via USB serial)
   • NFC Tag Reader
3. LCD (output via GPIO)

Features to develop

Please see https://github.com/unsatisfiedpopcorn/wheelchair_weighing_scale/projects/1 for features to develop

wheelchair_weighing_scale's Issues

Remove redundant code

Store Time with weight

GPIO button interrupts should be synchronous in order not to mess with the reading of hx711 values

this problem causes abnormal values to show on the display when taring

Change output from grams to kilograms

**Tare State**

The weighing scale will tare it's weight and calibrate

Store weight data on RFID tag

• Read weight data
• Write while preserving weight data
• Design trigger for the writing of weight (Once when the weighing scale stabilizes? -> conflicts with registration's use case)
• Integrate arduino and RPi, establish serial comms between them

Attempt to write weight to NON-FULL NFC fails

Decrease delay in arduino code without flooding serial buffer

**Registration State**

On encountering a new user he is prompted to take the weight of his empty wheelchair.

• Get arduino to write to NFC via serial comms
• Triggering serial comms to arduino via button
• Prompt user when a new RFID tag is encountered

Wisca should attempt to update the patient's weight ONLY when RFID is present

patient get on scale
patient's weight is measured successfully and it triggers a write to nfc tag even though no tag is there
will not write to nfc tag after this even though nfc tag is on the reader

Create LCD output