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Design problem with my project

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New Member
Friend i am using a CI-6535 respiration rate sensor with PIC16F877A...CI-6535 produces a 10V analog output but PIC 16F877A supports only upto 5.5V...So i want to convert this 10V to something below 5V so that if there is any change in the 10V output ---> below 5V output should also be changed...to monitor the breathing rate....

I couldnt use a regulator since it produces constant output for any input voltages

Plz help....


Well-Known Member
If you place two 47k resistors (in series) across the 10v signal from the sensor and tap off the centre of these two resistors, the voltage at the centre will be exactly half the voltage of the sensor.
You can now take this tapping to an ADC input of your microcontroller and get 256 increments.


Well-Known Member
Most Helpful Member
thank u very much

i will try and let u know
The 16F877A adc expects the input source resistance to be equal to or less than 10K, by using 47K's the conversion result could be inaccurate.

Use two 10K's [ or 4K7's] in series as a potential divider.

As the adc is 10bit, you can select for 1023 or 255 conversion counts, this is done within the program, not in the divider.
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New Member
Depending on your required accuracy you may want to use precision resistors and buffer the divider with a voltage follower.
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