# Implementation of an IoT Based Radar Sensor Network for Wastewater Management
## 3 Implementation and Results
### Sewer Pumpstation Universal Drawdown Device (SPUDD)
#### 3.1.1 SPUDD Design  
Summarised below is the field implementation design of the drawdown device. _Field Implementation Design_  
The radar device already comes with a top threaded chamber, shown in Figure 6, that uses an LCD screen to show measurements. We have completely added a new second threaded chamber to the radar and an extended plastic housing has been developed, large enough to contain all relevant prototype microcontroller (MCU) and printed circuit boards (PCBs). This is also shown in Figure 6 below. We designed the housing with IP68 rating in mind (for waterproofing). The deep thread, rubber O-rings and triple screw locking mechanism preserve the devices original IP68 rating. The grey screw cap on the end, shown more clearly in Figure 7 below contains a clear glass window to enable a view of the prototype boards, battery and real-time observation of status LEDs; including a flashing red to indicate the MCU searching for a Bluetooth device to pair, and a steady blue to indicate pairing to a Bluetooth device. This sealed, screw cap also provides easy access to the hardware modules contained inside. This design also allows for the ability to quickly connect a USB cable to the MCU for both charging of the battery and program modifications, as well as the capability to extract the microSD card from the Adalogger FeatherWing. Figure 8 below shows the current prototype bracket, comprised of aluminium plate, one bar is fixed whilst the other is adjustable via a ring screw to allow mounting on top of various sized SPS well safety grates. Figure 6: Portable radar chambers. Figure 7: Chamber two glass window. 2. _Testing Design_  
The portable drawdown device on-site setup and testing is shown in Figure 9 below. As also shown in Figure 8 above, the drawdown device is mounted firmly within the SPS well safety gates. It is important to note that the device must not be mounted directly above a pump as it may look like below, but in the space in-between pumps to avoid false measurements returning from the top of the pump as the well effluent draws down towards the bottom of the well, exposing the submerged pump. The experimental procedure included systematic testing of:  
1. A standard Direct-Online (DOL) pump SPS,
2. A SPS with soft-starters to control the power ramp-up/down, and
3. A SPS with VSDs to control the power ramp-up/down of each pump. At the outlined above SPSs, sixteen (16) tests were conducted on each individual pump to allow statistical confidence in results, utilising both the portable radar device and the common practice manual drawdown test with tape measure. Results were compared against one another, as well as against the quoted performance curves of the respective model of pump and its designed duty point. 3. _Mobile Application_  
In addition to the MCU programming, a simple Android Mobile/Tablet app has been developed to act as the user-interface for the radar drawdown device. The current mobile application chosen to interface with the radar device is pfodApp. The pfod acronym standing for 'Protocol for Operations  
Figure 8: SPUD adjustable mounting bracket. Figure 9: SPUDD on-site setup. Discovery', is quoted as allowing \"Control Arduino and other microprocessor devices from your Android mobile--NO Android Programming required\" [17]. This app acts as a data sink, and decoder of messages sent via Bluetooth from the MCU. The pfod protocol is a light weight protocol for simple device control and measurement. Each pfod message is specified to be less than or equal to 255 bytes in length, and is used to specify both objects, formatting and values for display on the pfodApp screen. The mobile pfodApp can be thought of as a micro-browser, displaying the micro-pages sent from the MCU.