Introduction: Haptic Feedback Device for the Visually Impaired [Project HALO]

Picture of Haptic Feedback Device for the Visually Impaired [Project HALO]
I recently watched an episode of Stan Lee’s Superhumans which featured a blind
man who used a series of clicks, like a bat, to echo locate his surroundings. I
got to thinking about other blind people and their ability to navigate freely –
without the use of a guide dog or cane. I came up with the idea to use a series
of rangefinders that would take input from sensors and output feedback to pulse
vibration motors placed on a person’s head. As a person gets closer to an object
the intensity and frequency of the vibration would increase – it’s directly
proportional to the distance of an object. If a region was lacking feedback,
then it would be safe to proceed in that direction.

I call my submission the H.A.L.O. - the Haptic Assisted Locating of Obstacles. I
believe this can serve very useful for the visually impaired to have the freedom
to possibily move about hands-free without the assistance of a cane or seeing
eye dog. Technology has undoubtedly made our daily lives better. By using a few
inexpensive components and sensors, I’ve made a device that will allow the blind
to navigate their surroundings and avoid collisions.

Step 1: Overview and Parts List

Picture of Overview and Parts List

Major Build Portions of the Project:
- Building the Halo
- Building the Motor Modules
- Building the Haptic Headband
- Wiring the Controller
- Creating the Software

The following is the parts list that will be relevant in the subsequent steps of this Instructable.  

 - Rigid frame (I used a round embroidery frame)
 - Female headers (for the sensors)
 - Ultrasonic Rangefinders (Parallax Ping Rangefinders)
 - Wire (Wires with male and female leads are convenient)
 - Glue
 - Twist ties to tidy up wiring
 - Soldering station
 - Male headers (for creating a bridge to feed 5v and ground
 - RJ-45-Term Screw Terminal (2)
 - RJ-45 Cable
- Marker

Motor Modules:
 - Vibration Motors (5) - Motot, VIB,3V/60mA, 7500RPM
 - Grid-Style PC Board
 - Male header pins
 - Motor "shroud" (to prevent things getting sucked into the motor)

Haptic Headband:
 - Headband
 - Sewing Kit
 - 5 Motor Modules
 - Wire (Wires with male and female leads are convenient)
 - Safety Pins
- Female headers
- Soldering station
- RJ-45-Term Screw Terminal (2)
- RJ-45 Cable
- Marker

Wiring the Microcontroller:
 - Arduino Mega 2560
 - Wire (Wires with male and female leads are convenient)
 - 5 LEDs
 - Darlington IC - ULN 2803A
 - 2 port screw terminal
 - 9v battery
 - 5v regulator

Building the Software:
- USB cable
- PC (for editing code and downloading to Arduino)
- Arduino
- Arduino development environment (
- Source Code, modified Ping.h library 

Step 2: Building the Halo

Picture of Building the Halo

There were a couple of key considerations for the Halo (sensor) portion
of the apparatus. It needed to be rigid in order to reliably range find
the right regions of the space relative to the user facing. I determined
that 5 sensors would be a good number between being overloaded with
information, and lacking sufficient detail and there being gaps in the
field of "vision".

Full Left (-90 degrees)
Left Center (-45 degrees)
Center (0 degrees)
Right Center (45 degrees)
Full Right (90 degrees)

1- Mark your frame at appropriate locations with a marker.
2- Cut female headers to 3 pins size (these are the receptacles for the ultrasonic sensors)
3- Glue headers to the frame at appropriate positions
4- Solder all the ground wires together (these are the left-most pin looking in to the frame)
5- Solder all of the 5V wires together (these are the center pins)
6- Run individual wire to each signal pin (right most pin)
7- Twist tie loose wiring to frame
8- Terminate all wires into a RJ-45-TERM. This will be sent over an RJ-45 cable to the micro controller for processing. 

Step 3: Building the Motor Modules

Picture of Building the Motor Modules

The Motor Modules create the vibrations against the skin to serve as the
haptic feedback. These motors convey the distance to the objects by
vibrating more intensely and in shorter intervals.

1- Cut your PC Board into small strips (enough for the 2 male pins to be soldered on). You will need 5 of these. I did this with my bandsaw.
2- Cut the male headers into 2 pins. You will need 5 of these pairs
3- Solder the male header pairs onto the PC board
4- Solder the motor leads to the PC board (direction is not critical)
5- Cover the motor in the “shroud”
6- Glue the PC board to the shroud, with the 2 male pins facing up 

Step 4: Building the Haptic Headband

Picture of Building the Haptic Headband

The key considerations for this were fairly simple. It had to be
flexible to fit to various user's heads. It had to bring the motor
modules to close proximity to the skin, and it had to minimize the
transferrance of vibration to avoid location confusion.

1- Put your headband on and mark the 5 key locations aligning with the sensor halo (Left, Center Left, Center, Right, Center Right, Right)
2- Sew 5 small pockets into the headband, large enough to receive the Motor Modules. These should be placed at the marked locations.
3- Cut the female headers into pairs of 2. This is to send the common 5V to the next and previous motors.
4- Affix the female headers to one of the male pins on the motor module.
5- Place the motor module into the pockets of the headband
6- Run wire to link the 5v common signal
7- Run individual wires to each motor module signal pin
8- Safety pin wires together and collect in back
9- Terminate all wires into a RJ-45 TERM. This will be send over an RJ-45 cable to the microcontroller for processing. 

Step 5: Wiring the Microcontroller Breadboard

Picture of Wiring the Microcontroller Breadboard

This section covers all the connections for the microcontroller and the main breadboard. I will not describe this textually, because I am providing the files for you (REFER TO WIRING DIAGRAM IN STEP 1- created with Fritzing). However, I will hit some high points and key concepts for you.

Key Topics:

Microcontroller Selection:
The Arduino Mega 2560 was selected because of the additional PWM pins it provides.
Please refer to for information about the HW, or the Integrated Development Environment (IDE)

Sensor Input:
- 5 of the Pulse Width Modulation (PWM) pins will be used to read the range values form the sensors.
- The input pins are coming in from the RJ45-TERM from the Halo.
- 3-7 are used for this purpose

Motor Output:
- 5 of the PWM pins will be used to send pulses to the motor through the Darlington IC. This IC connects a load to ground when and input (these 5 pins) are asserted.
- Pin 12 – Pin 8 are used for this purpose
- The output pins (its mirror across the body of the IC) are connected to the terminations of the RJ45-TERM heading off to the headband motors
- The “first stop” for these outputs from the PWM pins are the LEDs used in our debug array. Makes pretty blinky demos too!

Power Subsystem
- A 9v battery is used to power this configuration so we don't requre a wall plug
- The 9v battery terminals are wired to the Arduino Mega Vin and GND inputs, so this provides power to the microcontroller
- A 5v regulator is connected to the 9v terminals and this is sent to drive the Darlington IC (and in turn, the motors) so we have 2 power systems and the Arduino is isolated
- A 2 port screw terminal is used to receive the battery terminals 

Step 6: Creating the Software

Being a software engineer, I spent a lot of my time on the software aspect of this project. My source code is available. I used Caleb Zulawski's Ping Library ( I did make one modification, however. This library uses a default timeout of the pulseIn() function of 1 second. This was causing large delays in the execution of the program so I reduced this timeout to 500ms. Things execute far faster now. I will not go into the details of the program, because not all user of Instructables are code-jockeys, but here are the main points:

Source Code (Arduino Sketch and modified Ping library) are at

The flow of the main program loop() is:
- Fire sensor,
- Check to see if any of the motors are supposed to turn on or off based on previous range finding
- Fire next sensor.. Repeat

Other Things to Note As You Look At The Code:
There are 4 "intensities" of motor pulsing to give the person a better sense of the range, and these vary by the foot (up to 4 feet)
This is based on an state-machine model, but one of the Arduino threading libraries could be used to handle this independently.

Step 7: Taking It for a Test Walk

This was very gratifying.  We are all untrained users, and it does take some getting used to, but we all improved quickly.  It is hard to tell our brains to head in the direction where there is no buzzing when there is something buzzing.  That haptic buzz calls out for attention.  It was impressive to see my friends grasp what was going on, start walking with more confidence, and move around a room effectively with absolutely no vision.  As you can see, blindfolds were applied.  Note the end of the video when a chair is even detected.

Step 8: Wrapup/Conclusions

When I demoed the H.A.L.O. for a few friends and let them try it out (friends
who were seeing it for the first time and didn't really know what to expect) the
many uses for this device began to take shape - from navigating hallways to
being able to walk while carrying something to learning the lay of the land in a
new place. I was excited to see my friends walk blindfolded unencumbered and
collision free (please check out the video). It also made me think of various
modifications that I could make to the H.A.L.O.

What I’ve made is clearly a prototype and the components could be hidden in a
ballcap or visor in future models so it’s more user friendly. Additionally, the
version I made only has sensors 180 degrees around the head – you could increase
that to 360 to receive feedback in all directions or increase the sensor
sensitivity for farther distances.

I had a lot of fun working on this project and learned a ton. When we look at
everyday objects differently or truly think about ways we can use technology to
improve our lives it's amazing what we can come up with. I welcome your thoughts on this project. Good luck tinkering!


emattrose (author)2010-12-23

Hi polymythic, I'm so happy to read this instructable.
I worked on a very similar project last year, for the Intel STS competition. It also uses 5 sensors and vibrating motors to convey distance information to the user. I like your idea of placing the motors around the head - I put them on a belt, against the lower back. I suppose that makes sense because whereas you have the sensors spread around 180 degrees, mine all face forward at slightly different angles, so the feedback doesn't really need to wrap around the body. The sensor placement is an interesting design choice - I wonder whether it's more useful to have good resolution in front of your face or be able to sense things in all directions around you. I guess if you added enough sensors, you could have both! Too bad vibrating motors are so imprecise...
I haven't had chance to check out your code yet, I'm looking forward to it.
Best of luck, I'll be voting for you.

polymythic (author)emattrose2010-12-24

Great to hear from you emattrose. Sounds like you've been down this road! The sensor layout I selected because I wanted to be like "natural" vision with some peripheral. Someone else had commented on making the front stronger and peripheral weaker, which is interesting. The vibration sensors are a bit imprecise, but with the right material to minimize mechanical transferrance, you should be able to get some good resolution on the haptic. Hmm.. Perhaps one of those beds that you jump on and the next person doesnt feel it. The code still has some artifacts of my free play, so feel free to do whatever. Also I have heard of a threading library for Arduino which could have made my life easier than this crazy leapfrogging state machine with timeouts and scheduling.

lovemachinesix (author)2010-12-20

Great Job poly! Breaking new ground with something we've had access to for a long time. Such a great idea. I think using this with an assist from a can for the low stuff, curbs and the like, the blind could really speed up and move more freely in unfamiliar places. Really good idea. Good luck with this. Benmansfield's advice to hit up a sight center sounds right on and could really help refine the design and bring up some 'real world' issues seeing impaired have that sighted people aren't even aware of. Again... good luck man!

Thanks for the feedback. Agreed that the curb and low angle stuff is another part of the solution that should be integrated into the haptic picture. This project and people's commentary has fired up the mental gears thinking about assistive tech ideas.

bishopdante (author)2010-12-19

I think this is the coolest thing I've ever seen on Instructables.

I think it'd be great to do a glove which you can feel distance on, too!

Also, would be great for able-bodied people, eyes in the back of the head...

polymythic (author)bishopdante2010-12-19

Wow, bishopdante. That is high praise considering some of the AMAZING things that come up on this site. There are many directions to take this project for sure. Its a different experience having vision and using the device vs. being blindfolded. Your brain really does reach out for some data when you are blindfolded.

SaberToothTyler (author)2010-12-13

I seriously made an account just to tell you how wonderful this is... i honestly could see this being used by visually impaired people around the world. The idea is astounding. maybe a suggestion would be to put motors elsewhere as well as the head, it seems like it could get a little crowded up there with all the buzzing and im sure you have considered this, but still its such an astounding idea.

Thanks so much for your nice words. You are right in that if there is a lot of detection in an area, multiple adjacent sensors are firing. Teasing out the bit of quiet in the "hallway" situation (left and right firing, forward is no vibration) requires some focus and training. However, it is amazing that as a sighted person, when blindfolded, you quickly focus your brain computing on those stimulus. I would like to see how I do after being blindfolded with the rig for an hour or so.

comander01 (author)2010-12-13

Easily one of the most useful ideas on this site. I could definitely see this changing hundreds of lives. Possibly extend the range, and use a variable-vibration motor(if it exists), so that you can 'see' things across a room, and the vibration gets consistently stronger as the distance narrows. Also, perhaps if you used electric pulses instead of vibrations, the hardware could be slimmed down considerably. This is definitely worth patenting. I can also think of several military applications for a cheap, easy to use, set of night vision goggles that offer 360° vision.

polymythic (author)comander012010-12-13

Thanks for the comments, comander01. One of my design objectives was to keep the project at a resonable cost, but far more could be done with different sensors (Kinect, anyone?) The form factor can be considerably improved, I agree. I could get this into a normal hat. I do in fact use variable vibration motor. I use the PWM output for the intensity of the motor, and frequency between pulses as well.

Asif Abbas (author)2017-10-28

i have to design the same project please provide me the exact components list .

SudiptaR4 (author)2017-04-29


SudiptaR4 (author)2017-04-29


SudiptaR4 (author)2017-04-29

getting WProgram.h as a error in the source file.please help

SudiptaR4 (author)2017-04-29

i m getting error as wprogram.h in library file. pls help

EvanaE (author)2017-02-10

Can you please post or send me a text doc of the code.

ronald.ferreira.39 (author)2015-07-05

i invented an idea like this but a fake website davison invention stole it they have many lawsuits againts them for fraud

tolstoyan (author)2012-12-29

hi, we are having trouble with the codes. The following errors is below:

'RESCHEDULE_THRESHOLD_CONSTANT' was not declared in this scope.

In file included from HALO_Sketch_12_10_v8_2010.pde:15:
C:\Users\CAIMOL\AppData\Local\Temp\Rar$EXa0.454\arduino-1.0.2\libraries\Ping2/Ping2.h:22:22: error: WProgram.h: No such file or directory
HALO_Sketch_12_10_v8_2010.pde: In function 'int pingAndAdjustSchedule(int)':
HALO_Sketch_12_10_v8_2010:184: error: 'RESCHEDULE_THRESHOLD_CONSTANT' was not declared in this scope

Invento Guy (author)tolstoyan2014-11-14

Did you get your project running?

tolstoyan (author)tolstoyan2012-12-29

please we really need the solution ASAP

tolstoyan (author)2012-12-29

HI, we are already starting building your project but
we are having trouble with the codes. The following errors is below:

'RESCHEDULE_THRESHOLD_CONSTANT' was not declared in this scope.

In file included from HALO_Sketch_12_10_v8_2010.pde:15:
C:\Users\CAIMOL\AppData\Local\Temp\Rar$EXa0.454\arduino-1.0.2\libraries\Ping2/Ping2.h:22:22: error: WProgram.h: No such file or directory
HALO_Sketch_12_10_v8_2010.pde: In function 'int pingAndAdjustSchedule(int)':
HALO_Sketch_12_10_v8_2010:184: error: 'RESCHEDULE_THRESHOLD_CONSTANT' was not declared in this scope

polymythic (author)tolstoyan2012-12-29

Here is a similiar comment from another developer:

From: bchua3
Date: Dec 13, 2012. 8:01 PM
Subject: Project HALO

Hi Sir,
Good day to you.
I am actually trying out the project HALO that you submitted.
I uploaded the code to our Arduino Mega 2560 directly.
There were a few errors, the RESCHEDULE_THRESHOLD_CONSTANT was not found so I had to delete the // before it. Wprogram.h was not found as well so I had to replace it with Arduino.h as we are using the latest Arduino IDE Build.
I compiled the program and it was a go, however, the motor kept on spinning and it wont detect the proximity of the obstacle.
Any advice Sir?

Invento Guy (author)polymythic2014-11-14

Sir it's OK that he deleted \\ ,and he even replaced wprogram.h file with arduino.h . but what about his problem that motor keeps on spinning? And it won't detect proximity of the obstacle?
Please can you please give a solution to this?
If you have troubleshooted the code ,then please send it to my email id: maheshjshetty@gmail.comcom.
Please sir..!

polymythic (author)tolstoyan2012-12-29

It was commented out in the code for some reason. Just delete the // preceding the RESCHEDULE_THRESHOLD_CONSTANT up top.

Also, you will need to copy the ping2 library into /your_arduino_directory/library/Ping2

tolstoyan (author)polymythic2013-01-03

do i have to delete all these lines:

// RESCHEDULE_THRESHOLD_CONSTANT - Note: This may be replaced by "debouncing?" the motor
// This is the threshold over which the distance is large enough to trigger a
// reschedule event. If too small, there may be a lot of rescheduling, and if
// it is too large, then there may not be enough granularity.

or all these lines:

// INTERPULSE_LANTENCY (milliseconds) - Defines the period of time between when one ping
// fires and the next fires. This should allow for the sound to travel to
// its furthest detectable echo distance so that the next sensors RX will not
// pick up splash from the previous ping's TX. This may/will result in
// a lower than real distance result from the next sensor.

// MOTOR_PULSE_DURATION (milliseconds) - Defines the duration that the motor will pulse
// This is a constant at the moment, and the MOTOR_VIBRATION_FACTOR will
// shorte between the pulses of the motor

// RESCHEDULE_THRESHOLD_CONSTANT - Note: This may be replaced by "debouncing?" the motor
// This is the threshold over which the distance is large enough to trigger a
// reschedule event. If too small, there may be a lot of rescheduling, and if
// it is too large, then there may not be enough granularity.

OmarE1 (author)2014-11-10

your project is truly awesome and very useful ,bro . please can you send me the full code of your projects ? i want to build one for my self . all help is appreciated.i hope you can rely to me as fast as you can ...

OmarE1 (author)2014-11-10

the project is one of the most amazing ever . i would like to get the full code for the sensors please . all help is appreciated

amaproject (author)2014-05-22

It's a great project you've done it, so could you please provide me how

Darlington IC - ULN 2803A pins are connected in the circuit?

My email

Patuko (author)2014-05-02

Oh man you guys rock so hard :D

I was wondering to build a project similar like this and i'm seeing really hard work here about it! :D Really nice.

Did you guys have iterate on it? Seen here also another hactip project with a glove that also measures analog ir on fingers to vibe, really nice thoughts.

Will really want to know if you have been testing it on over this years and if you can "sense" enviroment better.

Thank you!

janandh (author)2013-09-12

sir will you please send me the source mail id is

polymythic (author)janandh2013-09-16

Hello! Source code is on the site in the instructable. It's fallen into disrepair because the Arduino environment has updated a couple times. I've made some modifications in the last year because others have contacted me. Way behind on updating. Will get to it when I've got time.

janandh (author)2013-09-12

sir will you please send me the source mail id is

janandh (author)2013-09-12

sir will you please send me the source mail id is

nolte919 (author)2013-05-05

DX sells an ultrasonic range finder for $3.20 (USD) shipped, $2.60 if you buy 3 or more. It would cut down on the cost of making this considerably.

tolstoyan (author)2012-12-31

when we do what you told we will not encounter another problem like bchua3 had? or we will also have this problem " the motor kept on spinning and it wont detect the proximity of the obstacle. " ?
also i really found it hard to use the figure 1 because in the figure the motor has only 2 pins while in the your instruction it has 3 pins hehehe im confused, i know i might be a burden but thank you for being understanding.

polymythic (author)tolstoyan2012-12-31

What is the debug output telling you. Look for //DEBUG. Also, this function fireAndPrintSensor should be telling you all kinds of stuff. What is the serial output telling you? It should be telling you the range and intensities. Do you have some debug output you could send?

// Display the range information
Serial.print("************ SENSOR ");
Serial.println(sensorNumber, DEC);
Serial.print(" Inches:");
Serial.println(inputSensorArray[sensorNumber].inches(), DEC);
Serial.print(" Feet:");
Serial.print(" Gap in Milliseconds:");
Serial.print(" Intensity:");

tolstoyan (author)polymythic2013-01-03

i will try to do everything you sent but i don't know how to debug can you instruct me how?

tolstoyan (author)tolstoyan2013-01-07

i hope you do not loose your patience with us, sorry for trying to do a hard project for a beginner like us. your project is perfect for what we want to build. thank you for your full support and i hope you will keep on entertaining our questions, this is my email "" i hope you can send us your old schematic diagram. also when i delete the RESCHEDULE_THRESHOLD_CONSTANT there is no error regarding about that but still the error C:\Users\CAIMOL\AppData\Local\Temp\Rar$EXa0.454\arduino-1.0.2\libraries\Ping2/Ping2.h:22:22: error: WProgram.h: No such file or directory pop up but i already copy the ping2 library in the my arduino/libraries/ping2. Again thank you very much and i hope yo will respond ^^,

tolstoyan (author)2012-12-21

hi polymythic remember me? hehehe we are currently building your prototype we have all the components ready and we plan to start working on it on 29th of december, just curious though, what is the LED for? only for testing? and if we are going to create the project itself, does that mean the diagram in part 1 will changed? i need clarity please reply ASAP tnx a lot :)

polymythic (author)tolstoyan2012-12-22

No problem. I am here to help. The LEDs are for debug/testing really. The motors do not come through well in videos, so the LEDS show how the motors are pulsed. Also, they do make nice debug indicators.

tolstoyan (author)polymythic2012-12-26

so it means that we can removed the LED's when doing it on actual? by simply eliminating the connection of LED's in the diagram, it means that the motor will be directly connected in the IC?

tolstoyan (author)2012-12-07

hello i hope you will respond, i seriously want to built this project, but i find it hard to software, which exact code do i have to use because i am very poor at programming. can you tell me which one of the files i downloaded from this page is the code, if it is not there can you please send me or email it to me please please i really want to know the codes thank you and GOD bless

polymythic (author)tolstoyan2012-12-09

Certainly! Here you are! Good luck my friend.

tolstoyan (author)polymythic2012-12-09

what is the folder ping2 for? can i install the program HALO_Sketch_12_10_v8_2010.pde directly to the arduino without doing any changes? i am confused, what is the purpose of the ping2 folder? please respond i have all the materials bought. i will post some pictures and videos after i finish your project tnx a lot :)

polymythic (author)tolstoyan2012-12-09

The ping library calls to the IO that is connected to the digital input (the motion sensor). If nothing is available immediately, it will wait. This is called a "blocking read". That will screw lots of timing up if it cannot read from the motion sensor. Ping2 just gets rid of that blocking read so the system can continue on its merry way.

Copy ping2 library into arduino/libraries/Ping2 and it should be good to go. You'll see the "include ping2.h" in the sketch.

tolstoyan (author)polymythic2012-12-09

thank you very much! your are so helpful i am building exactly what is in your instruction and if i hopefully understand it fully i might be able to make some modification hehehe but since im a beginner, i will make exactly this.
by the way im louie from the Philippines and a computer engineering thanks again and GOD Bless...

polymythic (author)tolstoyan2012-12-10

The diagram is in the instructable. I did not produce a schematic as such. You should be able to understand how to hook everything up by looking at the pin assignment in the code and making sense of the image in step 1:

Zoom in and the pins should be right.

tolstoyan (author)polymythic2012-12-10

im sorry if i am quite demanding hehe i dont want to put my components to waste if i made some mistake, coz items here in the philippines is quite expensive. anyway you really are helpful to your audience. wish you the best :)

polymythic (author)tolstoyan2012-12-10

No problem! The Maker Movement is about helping eachother out! Good luck from a friend in the United States!

tolstoyan (author)tolstoyan2012-12-09

last request can i have a copy of your schematic diagram :) tnx

About This Instructable




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