Posted by : AVINASH CHAKRAVARTHI Tuesday, 17 September 2013

  • blood oximeter (heart beat measuring from finger  )
 This project describes a technique to measure  heart rate through fingertip. The blood volume inside a fingertip slightly changes with heart beat as the blood is being pumped. This change in blood volume inside the finger artery can be detected with a simple optical sensor system and can be further amplified using appropriate signal conditioning circuit to generate a pulse of magnitude +5V. These pulses can be later counted by a micro controller to display the measured heart rate .
Circuit diagram: 

  • audio DJ mixer:
Circuit diagram:

  • distance counter while ur walking:

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking.
A beeper (excludable), signals each count unit, occurring every two steps. A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on.
For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both push buttons must be operated together. Obviously, this is not a precision meter, but its approximation degree was found good for this kind of device. In any case, the most critical thing to do is the correct placement of the mercury switch inside of the box and the setting of its sloping degree.
Circuit diagram:

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