Sensor Solutions | Symmetry Blog

Dec 18, 2019


Recently, an estimated 400,000 gallons of sanitary sewer water overflowed in Denton, TX, due to a pump failure, which caused wastewater to fill the Hickory Creek Lift Station, eventually causing an overflow.

The city cautioned anyone using water from a well within a half mile of the failure to boil their water for one minute before drinking, cooking or washing. Residents were also advised not to use hiking and biking trails in the area. All of which caused much frustration to residents near the sewage spill.

This crisis could have been easily averted if there were IoT sensors implemented to safeguard the pump’s intended operation. For example, a direct-angle hall sensor could have been installed on the pump to monitor the pump motor RPM and torque. MPS has both end-of-shaft and side-shaft variants.


Micronas has hall sensors for a plethora of measuring, monitoring and sensing motion. Their hall sensors can be used for RPM measurement, force/pressure measurement, rotary position, torque measurement, current sensing, leveling and stray-field compensation (among many others).


Temperature and relative humidity sensors from SiLabs could have been placed near the fluid pump in order to monitor for drastic sudden changes is the motor, pipe(s) or room temperature and humidity. Temperature and relative humidity can both be measured from a single DFN6 package. These sensors can come equipped with an ePTFE hydrophobic cover which is IP67 rated, meaning it is dustproof and can withstand water immersion to a depth of at least one meter.


After the pump failure, with sewage spewing into the lift station, InvenSense’s CHIRP ultrasonic ToF sensor modules could have been used to monitor water level rising where it should not have been. This new sensor family has many advantages of traditional infrared ToF sensors currently on the market. CHIRP has 500x lower power consumption, range and accuracy is not affected by ambient light or sunlight, sense any color target (including windows and mirrors), have 100x lower range noise and up to 5x wider field-of-view.


If pipes shifted or disengaged from their couplings, iC-Haus safety light curtain IC’s could have sensed this unexpected movement crossing the path of the pulsed LEDs and their optical receivers, thus tripping an alarm that a large failure has occurred.


An indicator from DB Unlimited could have been used to alert facility workers on site with an audible tone or alarm. These devices pack a very high sound pressure level into a tiny package. Only an input voltage is required to get a tone out of these devices, saving the extra work of design any external drive circuitry into a PCB.


In terms of controlling and reading each of these sensors and their data, the Digi XBee ecosystem would be a perfect fit. Data could be sent to the cloud from an XBee module via Cat-1, LTE-M, NB-IoT, or Wi-Fi. If multiple sensor nodes are required and a mesh network would like to be implemented, the XBee modules could be used in conjunction with a gateway (also available from Digi) to get the sensor data to the cloud. If this approach is preferred, the modules could transmit to one another over Zigbee, Proprietary 802.15.4 or DigiMesh. The diagram below gives a good overview of the various wireless technologies that could be implemented contingent on the number of sensors in the network and bandwidth required.


Configuring and programming the Digi modules is quick and easy in MicroPython and there are many XBee APIs and libraries available to further speed along the development process. To top everything off, Digi offers a device management platform called Digi Remote Manager. Digi Remote Manager is an industry-leading cloud and edge tool for rapid device deployment and easier asset and inventory management. Customers may access data from edge devices that were previously out of reach, automate mass firmware and software updates and receive detailed reports and real-time alerts on network health and device conditions.


If the sensors need to be battery driven, LoRa would be an excellent wireless technology to use due to its low power requirement and long transmit distance. Multitech has many gateways and modules to chose from. They’ve got mDot and xDot modules which are secure, regulatory-certified, Arm Mbed programmable, low-power RF modules, providing long-range, lot bit rate IoT data connectivity. These modules are LoRaWAN compliant, providing bi-directional data communication up to 10 miles line-of-sight and don’t require a monthly subscription like with cellular.


Symmetry offers a wide range of sensor solutions that could have prevented the pump failure in Denton, as well as the technical expertise to help Denton find the right component for their situation. If you are looking for a solution within your application, or technical assistance look no further than Symmetry Electronics. Contact us today!



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Why partner with Symmetry Electronics? Symmetry's technical staff is specially trained by our suppliers to provide a comprehensive level of technical support. Our in-house Applications Engineers provide free design services to help customers early in the design cycle, providing solutions to save them time, money and frustration. Contact Symmetry for more information.

Written By: Tyler Wojciechowicz


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