in my project i want to send measurement from humidity sensor to readout by SDI-12 bus . i fount in this page : ( http://www.daycounter.com/Circuits/SDI-12/SDI-12-Interface.phtml ) how to connect RX , TX , but with 3V3 , my arduino is 5V VCC !
anybody can help me to change the schematic to work in 5V ??

 

This way is easy: http://www.hobbytronics.co.uk/mosfet-voltage-level-converter

Though I'm not sure the 2N7000 has a low enough gate threshold for this circuit (should be 2V or less)

 

The BSS138 is used in 'commercial' level shifters, [ same 10K values].
They are SMT.
E

 

The BSS138 is used in 'commercial' level shifters, [ same 10K values].
They are SMT.
E

Yes, that's more like it. Or the IRLD014 is available cheaply and is 4 pin DIP.