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<videoflash type="youtube">KmyUX5ywaMg|700|450</videoflash> | <videoflash type="youtube">KmyUX5ywaMg|700|450</videoflash> | ||
The basic principle is the translation of the human blood flow into an electronic value. The photocell changes its resistance up to the light going into it. The resistance changes if fresh blood comes through your fingertip because of the decreasing of passing light. Two 546B transistors (operation amplifiers) switching the LED array on and | The basic principle is the translation of the human blood flow into an electronic value. The photocell changes its resistance up to the light going into it. The resistance changes if fresh blood comes through your fingertip because of the decreasing of passing light. Two 546B transistors (operation amplifiers) are comparing and switching the LED array on and off. Up to the size of the fingertip the sensitivity of the photocell (resistance) has to be set with a potentiometer. Due to some experiments and experiences i decided to use a combination of a fixed and a variable resistor (the poti). The variable resistance can be changed from 0-470 ohms which allows a fine threshold setting for the fingertip size. | ||
The sensor clamp is put in a box to avoid daylight coming into the photocell and bringing unwanted resistance values into the circuit. | |||
I also decided to connect a arduino board to read the values in a processing sketch (video below). With programs like Processing or Pd the pulse can change any value and transform it into graphic, sound etc. | I also decided to connect a arduino board to read the values in a processing sketch (video below). With programs like Processing or Pd the pulse can change any value and transform it into graphic, sound etc. | ||
<videoflash type="youtube">cCaQeeis1ug|700|450</videoflash> | <videoflash type="youtube">cCaQeeis1ug|700|450</videoflash> | ||