Operating HB100 backpack with Arduino Due
The articles and tutorials I've read on the subject say that the HB100 module produces a very weak signal which needs to be amplified before your Arduino can read it. They recommend building an op amp. This post on the Arduino forums, for example: http://forum.arduino.cc/index.php?topic=61989.0

BUT looking at your picture and linked article, I find that your device already includes the signal amplification and filtering you need in the backpack board. I found the store page for this module, which has a more noob-friendly explanation. From what I gather:


VCC: provide the module with a 5v supply.
VOUT: analog reading of the amount of return signal being received. My guess is you could use this with analogRead() to get a rough estimate of the size or distance of the object being read. If you want only the speed reading, you don't need this pin.
FOUT: digital output of the speed that the sensor is reading. Thanks to @sachleen's link, you can use either pulseIn() or FreqCounter library to measure the frequency and then convert it to a MPH or KPH speed.
GND - ground, aka common, aka -.


So connect VCC to 5v, GND to ground, and FOUT to an input pin on your Arduino. If you use pulseIn(), frequency f = 1 / t, t being the return value from pulseIn(). If you use the FreqCounter library, it no doubt has documentation on its usage.