what hardware do I need?

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hi All,

I'm a complete noob at this so please excuse any silly/dumb questions :wink:

I've had this idea - which may, or may not have been done before:

In the book that I'm reading they talked about a researcher that had built this headband contraption that had buzzers attached that would constantly alert the wearer where north was. After wearing this for a few weeks the wearer reported that his sense of direction had improved and he felt he could never get lost? Kinda cool, I wonder if it was built on an arduino using a GPS module??

So it got me thinking there might be a way to make a math tutor tool that uses sensory stimulation. I thought you could attach buzzers to each finger of both hands which would represent each number from 1 to 10 so when linked to a screen showing times-tables each buzzer will resonate on its matched finger? Then, to bring in another sense, you could have a musical note play for each number.

Finger/Number 1 2 3 4 5 6 7 8 9 10
Musical Note (key of C) A B C D E F G A B C

I thought the digit zero could be represented by buzzing all fingers at the same time and its associated note be a low G.

So, if you have the following come up on the screen:

20 X 4 = 80

The fingers 2, all (a pause) then 4 (another pause) then 8 then all would buzz. At the same time as the fingers buzzing the associated musical notes would play.

So, in theory you're, getting visual, kinaesthetic (touch) and sound stimulation for every calculation - which may help learn :slight_smile:

So, my questions are:

  1. What hardware do I need?
  2. Will I need the Arduino Mega because I want to drive 10 buzzers?
  3. Can I use the wave board I've seen on makeshed and drive buzzers at the same time?

Thanks,

p.

2

I wonder if it was built on an arduino using a GPS module??

If you're standing still, a GPS module can't tell where north is.

You need a magnetometer (electronic compass) to do this.

3

Hi AWOL,

I do believe the 'buzzer' triggered when the wearer of the device moved but no other technical details were given - I must re-read that section and Google the researcher...

Cheers, p.

4

Anyhoo, back to the problem at hand (forgive the pun).

I'm unclear why you'd want to associate times tables (presumably in base 10) with fingers, which I normally associate with base 1.

5

Base 1 as in a tally? like III = 3?

The reason I've chosen base 10 is that's the way I was taught when I was young - counting on my fingers (I still do it as I'm rubbish at mental arithmetic!). I thought a more logical way of doing it would be to start at zero (first finger - looking at your hands palm down this would be your left-hand little finger) then I wouldn't have to dream up something arbitrary for the zero...

6

The headband you mentioned is called a haptic compass. I have seen it done
with 12 motors and a belt. It uses a compass IC or a magnetometer. I just completed
a haptic compass design that was built into a neck-strap.

For the motors we used pager motors. You will need transistor buffers to drive
the motors but any ATmega board can drive the transistors. All of the low-cost
pager motors I have seen are around 75mA. In my design we only activated one
motor at a time to save the battery. If you cycle between the motors fast enough
you will not be able to perceive the cycling.

(* jcl *)

7

Just keep the motors (and their wires) well away from the magnetometer :wink:

8

The headband you mentioned is called a haptic compass. I have seen it done
with 12 motors and a belt. It uses a compass IC or a magnetometer. I just completed
a haptic compass design that was built into a neck-strap.

Ah yeah that was it - I suppose it doesn't matter where the feedback motors are placed as long as it's consistent...

Have you done any testing with yours? Have you found that you've 'learnt' from it?

For the motors we used pager motors. You will need transistor buffers to drive
the motors but any ATmega board can drive the transistors. All of the low-cost
pager motors I have seen are around 75mA. In my design we only activated one
motor at a time to save the battery. If you cycle between the motors fast enough
you will not be able to perceive the cycling.

Excellent thank-you - I have seen some vibrating motors but pager ones sound smaller - do you have any advice as to where I can get these? (I shall Google in a mo...).

I would like to be able to vary the speed of the 'application' based on user input (variable pot) - this way once the user is acclimatised they can increase the speed, or rather shorten the pauses, between each number.

9

Just keep the motors (and their wires) well away from the magnetometer

We did :wink: The compass datasheet recommends that high current traces (>10mA) be
it least a few cm's away. We also twisted the wires going from the PCB to the motors.

Funny you should mention stray fields. The OLED that I placed directly above the
compass (no other space available) had a speaker on it :frowning: I thought it was a ceramic
buzzer until my compass reading never changed. Since this app didn't need a buzzer or a speaker I removed it from the OLED.

(* jcl *)

10

When searching for 'pager motors' I found these - they're tiny and operate at nice low voltages:

http://www.precisionmicrodrives.com/product_info.php?products_id=182

11

Have you done any testing with yours? Have you found that you've
'learnt' from it?

This was part of a contract design that I did for MIT. They did a one week
trial in Venice last month. Too short a duration to "learn" direction.
I believe it takes a few months.

I believe the pager motors they used were ---

http://pagermotors.com/index_files/Products/DiskL/DiskL.htm

These motors would also work ---

http://www.precisionmicrodrives.com/product_info.php?products_id=92

(* jcl *)

12

Thanks JCL!

So, I know the parts coming together - a 'mega' board, transistors and the pager motors.

Any ideas about generating the music notes? I haven't decided yet whether have the application running on a PC and controlling the 'haptic' Arduino or whether I want the whole project to be standalone... I'm not sure whether I'd be able to control 10 motors, produce musical notes and have an LCD display all from one Arduino Mega?

13

You don't really need a mega. A board based on a '168 or '328 would work fine.
You just need to multiplex the motors differently.

I would prototype the application using the PC as the sound source. Send
your note generation commands to the PCB using the USB port. You can then
decide if you want a standalone board.

(* jcl *)

14

Thanks again JCL - you've given me a lot to go on :slight_smile:

Do you think I'll need (or could benefit from using) the motor shield?

15

I am not sure what circuitry is on the motor shield
(I usually use my own boards (www,wiblocks.com) :wink:

You will probably have a dozen or so transistors, resistors and connectors.
If the motor shield provides you a way to easily replace these parts it
could save you some of time. You could always start with a few motors (and
transistors) and see how it goes.

(* jcl *)

16

I've ordered an Arduino starter kit and some pager motors to start playing with :slight_smile:

Thanks for all your help - I'll let you know how I get on :slight_smile:

17

I have found websites that sell vibration motors that are half as powerful, but only cost $2.00 USD. These motors are lower quality (not as powerful, and precision microdrives must have some reason for selling their motors for so much).
http://www.pagermotors.com/Products.php?f_category=Pager

I also have found websites with hat version of this haptic compass with construction info and code for Arduino.
http://www.stanford.edu/~tanders/VibroHat%20Home.html

18

Thanks BillHo - great resources :slight_smile: