I am building a semi-automated book scanner which will be modeled similar to the one in the video at https://www.youtube.com/watch?v=62qrs7Rve8E. A book is placed in a V-shaped cradle and a v-shaped transparent glass platen moves down and presses against the book's gutter by it's weight thereby flattening it. At this point 2 digital camera's on either side take picture of each of these book pages. Once the photos are taken the glass platen moves back to upper position, the operator flips the page to the next and then the cycle continues until the book is finished scanning.
I am planning to use a stepper motor with a pulley system (as shown in the below picture)
to motorize the v-shaped glass platen up and down movement. I want to know how i can exactly halt the glass platen (driven by the stepper motor) during it's downward traversal at the time of it pressing against the book's gutter. The challenge is that different books gutter height varies depending on the thickness of the book and so and i cannot fix an exact distance from top to bottom and if at all i do so, then if the book is thin or small the glass platen might not reach till the book gutter and if it is too big then it will keep pushing the book gutter forever. I have thought of using pressure sensors, photo interrupters etc but I was also thinking
if there is a way to monitor the motor drive current which would be likely to increase when the motor is stalled, or to detect the end of platen travel by monitoring the rotation of some part of the travel mechanism which would cease rotating, that could in principle be detected electronically using some kind of sensor.
Any thoughts, ideas or suggestions would be highly appreciated.
Bokks
