Can I use LPS25HB to measure the pressure of foot stroke

[Rahul Kumar]

Posted on June 01, 2017 at 13:56

Hi All,

I wanted to use LPS25HB for measuring the pressure of foot stroke while running. Can this sensor be used for the same. Is this activity realizable using this sensor ?. I checked the datasheet and it said it is a kind of digital output barometer. 

Thanks

Rahul

Posted on June 02, 2017 at 11:19

Hello,

It depends on other circumstances, for example physical setup of your measurement device. Please note that LPS25HB is an air pressure sensor, so some kind of air 'cushion' needs to be incorporated. You could try putting the sensor into a box of sealed air (for quick evaluation, try a plastic food box with a sealing).

The calculation below is just a rough estimation:

Pressure is defined as force per area (p = F / A). Force is defined as weight multiplied by earth's gravity constant (cca 9,8

m/s^2

, but let's say 10 for simplier calculations), meaning F = m * g, for a standing person ca. F = 80 kg * 10 m/s^2 = 800 N.

Area of a foot (only one is being stepped on during a run) could be 1 dm^2, which means if you step on a box with atmospheric pressure inside, with one foot, you could increase the pressure by p = F / A = 800 N / 0,01 m^2 = 80 000 Pa.

The range of this sensor is just 25 000 - 125 000 Pa. and the atmospheric pressure is cca 100 000 Pa, so stepping on the box will give you about 180 000 Pa, which exceeds the range.

David

Posted on June 02, 2017 at 13:19

A few more ideas:

One or more load cells could tell you the weight. Have a look at this article: 

https://learn.sparkfun.com/tutorials/getting-started-with-load-cells

 . However, to determine pressure, you would have to know the foot area. This means in order to determine a pressure applied to your foot, you need to measure the foot first.

You could also use an accelerometer to get the idea how rapidly is a person running. Either put them in shoes or inside a running belt.