Reducing 5v to 3v for BMP085

I am kind of new with this and wanted some help with voltage reduction. When i reduce 5v from the arduino uno to 3.3 volts using resistors to supply a BMP085 sensor, the sensor stops outputting data to a serial connection. I calculated the resistors to use for proper reduction so that the voltage falls within the acceptable parameters. When i plug the sensor directly to 3.3v it works correctly. What am i missing?. I am trying to use 1 voltage supplied from the arduino and reduce it as needed for the sensor. In this case 5v, because i have other sensors requiring 5v.

I’m assuming that you’re using the Uno’s 3V to run the BMP085 with and that you need to make the Arduino 5V I/O suitable for 3V I/O.
One of the members has been doing up PDFs of circuit building blocks.
Refer to “bi-directional voltage level converter”
http://www.pighixxx.com/pgdev/ABC/disp6e.pdf

Thank you for the quick response. pardon my ignorance, but in the top 2 examples what does the in/out represent?

mateojaime07: ...in the top 2 examples what does the in/out represent?

You should be concerned with the circuit on the left, but "in/out" is the connection to the device I/O; it is "Bi-directional", so it is good with pins as inputs, or outputs, or both. The "in/out" terminal on the left goes to the 3V device and that on the right is for the 5V device.

OK?

yes that makes sense thank you very much. I will give it a try and report back if needed. thanks!