Hi everyone,
You really need to be using a buffer between the Netduino and the relay.
There are two hazards connecting it directly:
Both hazards could destroy the output pin and possibly other parts of the Netduino.
- relay coil draws more current than the Netduino can handle,
- back emf causes a voltage spike on the Netduino output pin.
To add to what Paul said, you really should add a pull-down resistor. Yes, you can specify when you create the OutputPort that you want it to be internally pulled down, but what about the 2-3 seconds that it takes for the Netduino to boot up? You don't want to have the state floating. If the pin floats high, it would cause the relay to trigger. While in this case the worse that would happen is the camera would take a picture. If what your triggering happens to be the mains, or a garage door, or some other device it could create a real safety hazard.
To add a pull-down resistor, add a 4k3 (or 10k) ohm resistor between the base of the transistor and ground. This will ensure the pin is *always* in a known state. Its either at ground, or high because you've commanded the pin high.
-dan