I want to measure length of foot using infrared.Need help!

[Ebald]

led to measure length

I am thinking of designing an electronic device that will measure your foot length and display the foot size in LCD or LED.

The first option i think of is using infrared because it seems to be easier to implement. Anyone out there can give me a suggestion on how to measure the foot size?

 

[barath_87]

australian foot size measure

Keep an IR diode and a receiver pair spaced at every inch( your resolution will be an inch).Pulse these IR LED's with say 36Khz signal and use a TSOP1236 receiver.Follow it with a priority encoder...

 

[Ebald]

how to measure length electronically

My lecturer said pressure sensor might be a good idea as well because we dont need many IR receiver and transmitter and might be more accurate. Imagine if we only place it at every inch then the measurement of less than an inch might be neglected. He was suggesting pressure sensor where the whole foot can be measured but again i dont know how to build this sensor exactly. Anyone has any idea?

 

[BABESH]

a.m .infra.neede

How can u measure distance/length using a pressure sensor,

probably it may help to detect whether foot is placed or not.

 

[Ebald]

how to measure foot size

My lecturer was saying in the market there is a foam where the resistance changes when the pressure on the foam changes. I am assuming mayb when u increase the pressure, the foam will increase the resistance. Therefore, he was suggesting a grid method where u place multiple conductor across the foam with even spacing and send current(or some sort of signal) through each conductor. The place where the foot is there, the pressure is high and thus the resistance is high and as a result the current through that grid is going to be lower as well. So, u can tell whether the foot is there and you will know how many grid lines has lower current. Since in the beginning we use even spacing between the grid line and now we know how many grid line has lower current, the work left is just multiply the number of grid line with the spacing and we get the length.

Using this method, he said u save cost as conductors are definitely cheaper than IR transmitter and receiver and doesn't require mechanical part. However all these are theory, i havent really built a pressure sensor before. I am not sure how to send signal through those grid and i also don't know how to build an electronic equipment that will help me to identify the signal that is lower and calculate the length for me? Could it be some sort of adder or multiplier which will do that job?