About: A normal nerd filled with ideas, working on projects which benefit people and environment. Want to educate people about my projects and ideas... Interested in learning from others toooo.......

Many people with physical inability caused either due to disease and injury cannot interact with the outside environment. They cannot easily engage in the simplest act of interaction with the outside world. Assistive Technology which was developed for the disabled range from simple electronic gadgets to complex level .The proposed project is for people characterised by severe difficulty in making planned movement (apraxia-most dreadful disease). This project involves the use of gesture controlled switch action for control of various house hold appliances wireless. The project is aimed at persons with less than 80% of disability and provides access to all day to day household appliances. This provides them FREEDOM and independence from other people's help.

The concept deals with providing the apraxia person with an ability to switch on/off of a portable fan [or any other appliances] whenever the person wants to just by the movement of their body part. The only reliable movement of persons with that of apraxia appears to be that of hip which lifts the left knee. The challenge is to harness this movement to activate a switch device to control the device. Primary circuit consists of an accelerometer which is attached to the body of the disabled person. The output values from the accelerometer are fed to a comparator circuit and microcontroller circuit before sending it to the transmitting circuit. Secondary circuit consists of the receiving circuit along with a relay board to open or close the circuit according to the data received. By this action one can control any home appliance according to their need. Here, the proposal is based on a person who has apraxia, where one can move his/her leg to a particular lift angle.

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Step 1: Monitoring the Persons Need

The disabled person here wants to switch on a fan [ consider this case it to be fan ]. He lifts his leg to a particular angle to a certain height (say 10cm). The fan goes ON by the movement of his leg.

But in some cases if he moves his legs involuntarily then it may go ON. To avoid this I have included a special angle measurement where you can adjust it accordingly to the user.

If a person wants this device in his arm then the strap can be tied to his arm. So it provides you with a configurable use.

Step 2: Basic Working & Block Diagram

By the block diagram, the accelerometer is coupled to the microcontroller.

The data sent by the accelerometer is processed by the microcontroller and then transmitted by the transmitter.

The receiver receives these signals which is then processed by the signal conditioning system (basically a op-amp system).

This signal triggers a relay which puts the device in either ON or OFF state.


  1. Accelerometer
  2. Arduino Board Microcontroller
  3. RF transmitter
  4. RF receiver
  5. Signal conditioner-Op amp LM324
  6. Relay HRS4-S-DC3V
  7. Transistor 2N2222A

[ Here I am using a TEXAS INSTRUMENTS CHRONOS WATCH eZ430 so we won't be needing the 1-2-3 materials ]

Step 3: Primary Circuit : Construction & Working

Here in this proposed model I have used a TEXAS INSTRUMENTS CHRONOS WATCH (eZ430) which embeds almost all of the primary circuit. It can be easily found on the TI e-store.

It comes with a built in accelerometer sensor , microcontroller and RF transmitter ( and many more but this is what we need ). It has a powerful compact MSP430 microcontoller in it and a RF transmitter of great range.

In order to test and show how it works, here is small demonstration when it is connected to a computer.

[ NOTE : By default the Ti watch comes with a watch and receiver which is separately given which is used to interface with the watch and computer]

Enclosed Images : TI watch and its RF receiver

The accelerometer data from the watch is read by the microcontroller and can be transmitted to the RF receiver via built in RF transmitter.

Step 4: Reading the Accelerometer Data

By connecting the RF receiver ( the white pen drive like thing ) to the computer and by running the Control Center Program (Driver software of chronos watch) one can see the output for the various accelerometer movements.

In one figure the accelerometer seems to be steady on all axis as the watch is stationary.

In another figure when one tends to shake the watch up and down the respective axis values changes accordingly.

In the last image when one tends to move his leg in a particular value we get this sharp curve which is the key of this idea.

This data can be readily transmitted by the microcontroller just like transferring the data to the computer to the Secondary circuit.

Step 5: Secondary Circuit

In this circuit, it encloses the RF Receiver, signal conditioning , a relay and finally the output.

We connect a comparator to the relay using a transistor which will act as a switch. We connect the comparator to the base of the transistor so that when the output goes high it turns ON the transistor which acts as a switch and provides a path for current to go from the positive supply through the coil of the relay through to ground.

Here I designed a EAGLE CAD model of the circuit which encloses the signal conditioning unit, relay & some filters and made a ready made PCB for the same.

As said before the RF receiver is coupled to this unit for the signal detection and amplification purpose.

Step 6: Triggering the Device

Finally When the RF receiver reads a signal from the RF transmitter, the signal gets amplified and gets transmitted to the Relay network.

Our output is going to be a switch. We aregoing to use our switch to complete the circuit connecting a battery supply and some device which we will have set in an ‘on’ condition.

We will need electrically controlled switch – these are called relays

Electromechanical switch comprising an electromagnet and a set of contacts and a spring.

When the electromagnet is energised through the application of current it attracts the armature towards it which causes the contacts to be made. When the current stops the spring opens the contacts again.

The contacts when can be normally open (NO) or normally closed (NC). Many relays have two sets of contacts where one set is NO and the other is NC. Through using a relay the output of our circuit is indistinguishable from a normal switch, i.e. from the point of view of the output it is a switch so we can connect it to things we want to switch on/off – as required in our design brief.

Finally the disabled person can turn ON or OFF the device remotely and has complete independence !

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    3 Discussions


    5 years ago on Introduction

    Interesting idea. Is this something you have actually made?

    Kiran Raj
    Kiran Raj

    Reply 5 years ago on Introduction

    Ya buddy ! This is my mini project at college which is being funded by GOVT. OF INDIA , under Dept. of Science & Technology. Since it is in IEEE paper proceedings i'm not entitled to leak all the data in public !
    Any help sure mail me !
    And please do VOTE for me !


    Reply 5 years ago on Introduction

    Cool. This is a good idea, glad you are pursuing it. Good luck!