# How to measure weight while walking

For a school project, I need to develop a way to measure a person's weight while they are walking. If that weight exceeds a preset amount, I need to have an alarm sound. Any ideas?

Is this a platform that they walk across?

And should be the accuracy of the measurement while walking?

This is very interesting. if Polar can measure the average speed and distance with the accelerometer attached to running shoe, what the heck, why should not this be possible?

Cheers, Kari

Ideally, it would be measured by something attached to their shoe.

You’ll need some kind of force sensors in the shoe. Perhaps something like this: http://learn.adafruit.com/force-sensitive-resistor-fsr I’d put one in the heel and one in the toe, under the insole. I’m guessing that when the force is equal on heel and toe the force will be proportional to weight. The signal is likely to be noisy so you should probably average a bunch of samples.

Seems odd that one might expect a person’s weight to change while walking.

My interest in this case is that how much I sweat in two hours of running. Than depends on the air temperature and intensity of the training.

And the other thing is; it would be nice to know if that can be built! ;)

Cheers, Kari

f=ma
If you want to find someone’s mass, you need to know the acceleration and the force. The force can be a FSR, but if the person’s feet are moving the acceleration will be changing. A good runner can probably impart hundreds of pounds of force into the ground, many times what they weigh [citation needed]

Of course, if you can get them to stop running for a second simple force sensors are all you need unless you’re operating on another planet.

This is a whole different story to measuring average speed etc.

As the forces will be dynamic I think it will be very difficult to measure anything. The force applied to a foot will vary with every step but the runner's weight doesn't.

Rob