Posted by Faisal Shah on November 10, 2009 at 7:32pm
I'm considering using the MPX4115 absolute pressure sensor for altitude, and the MPXV5004DP differential sensor for speed. These are both 5V parts, and my microcontroller is 3.3V. What would be the optimal way to connect these sensors to my uC's ADC inputs?Would a voltage divider suffice? What if I were to put an RC filter on the output of the pressure sensors (as suggested in the application note (http://www.freescale.com/files/sensors/doc/app_note/AN1646.pdf) ? Should I buffer the output of the RC filter with an opamp, then use a resistor network to scale the voltage down to 3.3V? Or just put a resistor network immediately after the RC filter and tap the output to the ADC?
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Given that the RC world (servos and Rx) work at 5V, you might want to think about switching to a 5V microcontroller and running the whole board at 5V, like we do.
Hi, MPXV5004DP zero pressure voltage is close to zero, so you can use it as is, assuming that you are not reaching speeds where sensor output voltage exceeds 3.3V. MPX4115 voltage, however, is close to VCC (5V), so I use resistor bridge to bring it down (I use 10k and 20k). I think that simpler is solution is better.
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