vehicle driver hand's force sensor

[zhmur]

Dear Members,
i am building a vehicle security device that detects driver fatigue based on his eyes closure and the force he applies on the steering wheel. combining these two features i hope to achieve a better accuracy of the device .

For the eyes tracking part i use a an Ir camera that will be pointed to the driver face, connected to processing unit which analyses frames and detect eyes and their percentage of closure continuously
For the hands force detection part, i liked the idea of using multiple small sensors mounted in the steering wheel perimeter, connected together and to a processing unit with flexible cables " **broken link removed** "

i searched the web for small size , cheap and accurate force sensor and i found the Bosch high precision pressure sensor BMP085, https://www.sparkfun.com/datasheets/Components/General/BST-BMP085-DS000-05.pdf
but since it s designed to measure pressure variation i am in doubt if it s really what i need for my project, please help me to make the right choice for sensor.

 

[BradtheRad]

It could also work to attach tiny push-switches to the steering wheel.

Whether you use sensors or switches, you'll need to put some sort of semi-cylindrical plates over them, to catch pressure of fingers across a range of a few inches.

I think it is possible to get sleepy and continue to maintain hands on the steering wheel.

I once saw an article telling how researchers attached a level sensor to drivers' heads. If the driver got drowsy and started to lower his head in any direction, the level sensor detected it and buzzed in his ear.

Reports said it worked well. Supposedly there were plans to market them commercially, but that was the only time I ever heard of this method.

 

[zhmur]

first of all thank you for your answer, about the level detector yes i saw it in china just 2 $ attached to the dirver's ear, it could buzz or vibrate if driver gets sleepy, i will think to add it in combination of driver hands pressure and eyes closure.
About the switch, isn't a push switch only has 2 states : 0 and 1 ? i think it can't measure any variation, it's either a "yes" or "no" signal.. i m thinking to measure the pressure < force > applied by the driver because it will be more meaningful.
could you please tell me if you know a reference of a sensor that can fit to this application?

 

[BradtheRad]

You are looking for a pressure sensor which is a few inches square, and which can send an electronic value indicating the amount of pressure where a finger touches at any spot on its surface...

That is a tall order.

The closest thing might be a proximity (capacitance) sensor. Perhaps a sheet of aluminum foil which is connected to an oscillating circuit. Spread a sheet of insulator over the foil (cloth, etc.). The tighter a finger holds the wheel, the closer it gets to the foil, and the more it changes the oscillating frequency. It will require some experimentation.

Another possibility. In a Radio Shack book, Forrest Mims described a pressure sensor made from a piece of flexible black foam that IC pins are embedded in to reduce static charge. Its resistance is supposed to go down when it is held between conductive plates, and squeezed. Some pieces of the stuff are more rigid than others.