problem with sensor and 8051. its urgent

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torana

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sir
iam using SPO2 sensor with at89s51 microcontroller. i think i will go for ADC also.

but i dont know the pin details of sensor, i mean where to give VCC and ground. what is the supply voltage and which one is the data line.

for sensor details please follow the link: https://www.sunrom.com/376


thank you sir.
 

You put a AC coupled, current limited square wave across pins 2 and 3, this then switches on the two LEDs one after the other. You then feed pin 5 via a high value resistor from some voltage source, the voltage then at pin 5 will be a square wave offset from 0V. The ratio of the two levels will be the ratio of the de-ox to ox levels. i.e. if its 100% then you will get just a dc out with no change between the two readings.
Frank
 
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    torana

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thank you sir. i dont know how to put a AC coupled, current limited square wave across pin 2 and 3.
waiting for peply

thank you.
 

For a start the current rating of the LEDs is unknown, most will handle 10 mA*. lets use a 5V supply, the LEDs will drop about 2 V, so feed both lines from the 5V supply via a (5-2)/.01 = 300 ohm resistor. Now connect two NPN transistors, collectors to each resistor/LED junction, emitters to earth, leaving the bases free. Now when one transistor is on, it shorts out one LED and makes a current path for the other. Feed the output from a multivibrator or a square wave from your micro into the bases via a 4K7 resistor with each base getting an out of phase signal. i.e. when one output goes positive the other goes to earth.
* Check this with manufacturer
Frank
Frank
 

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