Omp amps have a purspose?? Yes!

Spring break is upon me and instead of gracing some tropical beach to knock back a few fruity drinks while listening to Margaritiaville I am striving to finish my senior design project.. Todays hot topic was using the Flex sensors to determine the weight of product in the bowls which tips a scale. the data sheet for these guys is here: Flex Sensors A resistance claim of 10-20k Ohms depending on how drastically one bends it. we are in a hard position where our sensor ranges from 13-14k Ohms. this produces a small window of voltage change between 2.08 volts and 2.17 volts.

Not bad though we are using an OMP AMP! here is a picture of a basic inverting amplifier. We see in this one that the (+) input to the circuit is grounded. This needs to change to a voltage that we can use to make the low voltage aka 2.08 volts to equal a gain of zero and the 2.17 volts to equal a much larger gain. Since the window is small here our relationship between the flexing and final voltage output (between zero to 5 volts) is going to be quite linear. We did some math and plugged the numbers into MATHCAD (Here is the link Mathcad ) and voila we have an answer for the value of the R2 and the voltage offset. Note though in order to understand what is going on here you need to know we used a Thevinin Equivalent circuit to represent the voltage divider created by the flex sensor on top and a 10k resistor on the bottom.

The circuit may need a little bit of tweaking as we are assuming the op amp is ideal but I am confident we can make it work.

Tomorrow I am actually going to go somewhere. I am taking my Lovely girlfriend to the Museum of Science and Industry. I will be thinking of senior design but hopefully I will be intrigued by the Body Worlds exhibit (Link http://www.bodyworlds.com/en.html ). My philosophy is that if you're going somewhere cool or scenic why not learn something or work up a good sweat. you'll be surprised how much fun that is and if the place to a lot of sweating to get to it certainly won't be that crowded.

To-ta-loo everyone