In previous post, I explained how the schematic works. To illustrate this in action, I have added a LED in series with 150Ω resistor as load and wrote a wee application that controls the thyristor.
For those of you that may wonder where this becomes practical: the goal of this project is to switch on or off the power of any schematic, attached and controlled by Netduino. One example is the problem when you power Netduino and a motor driving schema starts the motor just because Netduino pins are in a high state. You can list here as many other cases you want. The solution I am showing here, allows you to control the power (like electronic power switch) of any such schematic. Just consider SCR cathode as + end of a power supply. Of course, you can consume only what Netduino’s 5V pin can give you so check the specs.