We will consider a simple scenario similar to the previous chapter, to develop a simple light intensity monitor system with a device that monitors the light intensity (lux) inside a room of a building and a remote device that acquire the values. The system is based on MQTT with a Mosquitto broker running on a PC with Windows Embedded Standard as you will see in the next chapter. The device with the sensor is based on Compact O.S. and it publishes light intensity values on a topic and the remote monitoring station subscribes to this topic to receive updated values. In this example, the subscriber and the broker run on the same machine (PC with Windows Embedded Standard).
Regarding the light sensor, you need the InterfaceKit 8/8/8 and the precision light sensor from Phidgets. The InterfaceKit is a module that you can connect to the Compact based device via USB and it provides 8 ports to connect a wide variety of sensors.
Figure 7.2 : Phidgets InterfaceKit 8/8/8
The precision light sensor measures human perceptible light level in lux; its measurement range is from 1 lux (Moonlight) to 1000 lux (TV studio lighting). You need to connect the sensor to port 0 of InterfaceKit (the port 0 is only a choice, you can change it but you need also to change the source code that refers to port 0).
Figure 7.3 : Phidgets precision light sensor
Now you are ready to write the publisher side source code for a new Internet Of Things application !