Member Since: July 10, 2006

Country: United States



Electrical Engineer with a broad range of experience from circuit and chip design through application and web development.


janitor through owner


danjuliodesigns, LLC. Giulio Lighting

Spoken Languages


Programming Languages

PIC assembly, C/C++, Real Studio, scripting languages, device-specific languages


University of Colorado


Circuit design, firmware, application level development


Embedded systems


www.danjuliodesigns.com www.giuliolighting.com

  • I am confused how the level translator for DIN is supposed to work connected to an Arduino TX line that also has a series 1k resistor (such as the Sparkfun Arduino Pro 5V). Q1 is normally off because Vgs = 0 (g = 3V3, s = 3V3 via R5). When the Arduino pulls TX low then the voltage at the drain will be around 2.5V (as a result of the voltage divider created by the two 1k resistors - one on the Arduino and one on the shield). The FET’s body diode should conduct but will only drop DIN a little (2.5v + Vf of the diode). This won’t meet the logic low level requirements of the XBee.

    The circuit would work without the series resistor on the Arduino or when connected to D3 with the Switch set to DLINE because IN will be pulled to almost 0V and DIN will be pulled to within Vf of that voltage probably meeting the logic low level requirements of the XBee. The circuit will also probably work with the Arduino’s 1k series resistor if R6 was 10k instead of 1k because the low level voltage would be 1/11 of 5V or ~45 mV.

    Am I missing something?

  • Accurate and easy-to-use. I posted the design and source of a simple 4-channel monitor/logger using this device, an arduino and EA DOG-M LCD display using the libraries listed here to my website if that’s of any help to anyone.