FlexiForce Pressure/Time Measurement

cdub

I would like to build 1 or·more pressure sensitive mats for performance measurement using the BS2
for a 100lb person.

Here are the scenarios:

1) Person stands on floor next to mat, jumps onto mat then quickly jumps off. Measure how long they were on the mat before jumping off.

2) Person stands still on mat, jumps straight up and down on the mat once. Measure how long they were off the mat.

3) Person stands still on mat, then jumps off mat on queue. Measure reaction time.


I have the flexiforce sensor and the demo is about·at my skill level since it provides a pictorial and the BOE though I have the homework board).

Is this the appropriate sensor to use?
Do I need 3 separate setups?

Tristan T

The flexiforce sensor is for measuring a force (or weight), however you seem to be measuring binary (on and off) values. All you need for this is a switch. Also, consider that a 100lb person applies 100lbs of force to the sensor when he is standing still. When that person jumps he will be applying significantly more force downwards than 100lbs to accelerate himself upwards; this will be above the 100lb max of the flexiforce sensor and you won't get meaningful data.

I would suggest that you go through the What is a Microcontroller book here:
www.parallax.com/dl/docs/books/edu/wamv2_2.pdf
and try and create a similar setup using a pushbutton switch, and once you have built a program/interface that works with a push button, you can then consider scaling it to work with a person jumping on a mat.

Tracy Allen

We used a resistive device similar to the flexiforce to monitor for desert kangaroo rats on feeding trays. It was time/activity and also a question of rough weight. The tray was a triangle with one sensor at each corner,, and the sensor resistances in parallel. Since the force is proportional approximately 1/R, the total (1/R1 + 1/R2 + 1/R3) was approximately proportional to the correct sum of the forces. This was a sensor formulation for light weights.

These sensors do not survive shear stress or abuse at all well. If you do this, then make arrangements with a rubber or gel mat under a platform or something like that to spread out the force and to direct it straight down on the sensor. If you just need a yes or no signal, one sensor would be fine, or as Tristan suggested, something just using a switch.

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Tracy Allen
www.emesystems.com

cdub

Thanks for each of your responses.· I've worked through most· (1/2) of the WAM exercises.· You switch suggestion does make sense. I'm heading in the direction of the type of door mats used at halloween.

Here is a link to an inexpensive mat that approximates the interface. I'm wondering how I can connect it to the BS2 as a switch:· http://www.maplin.co.uk/Module.aspx?ModuleNo=3091&TabID=1&source=1&

Alternatively would the BS2 be able to·interface with·the B201 FlexiForce model as easily as the low-weight version as seen in this link? http://www.tekscan.com/pdfs/Brochure_Flexiforce.pdf



Thanks,

Cdub