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Development of a Sensor Spear

Paper Type: Free Essay Subject: Engineering
Wordcount: 5277 words Published: 18th May 2020

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Development of sensor spear to go into silos of grains or nuts.



To develop a sensor spear to go into grain silos, which continuously log the data from the humidity, temperature, pressure sensors using ESP32 and view the data using LoRa (Long-range sensor).



  • To assemble the sensors and make necessary connections with ESP32 on a PCB.
  • Log the data for every 2 minutes through the sensors.
  • Making the sensors talk to LoRa, in order to view the data online through the internet.

Problem statement


In agriculture, due to a lack of technology usage, industries face some losses. The main problem for the farmers is to store the grains and make sure there is no grain loss due to certain factors like insects, mold, chemical residues. On-farm grain storage systems should be well maintained in terms of humidity, temperature and pressure factors. There are some ways such as pits, grain bags to store grains on-farm but silos most preferred. Silos are considered to be one of the most effective ways to store grains in Australia. Controlled atmospheric conditions, maintaining required humidity and pressure factors are the key challenges in this process of storing grains on-farm.



In the field of agriculture, farming is nothing but growing crops and farmers face a lot of difficulties before cultivating as well as after getting the crop, in many ways such as natural disasters and grain storage issues due to lack of technology. Once upon a time, underground grain storage is one of the main methods practiced. Technology plays a major role in the storage of grains as it is difficult to maintain the temperature, humidity, moisture and pressure factors inside the grain storage systems called silos.

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To optimize an on-farm grain storage facility we need to meet some requirements and careful planning is a must. These storage systems can provide both short-term and long-term storage facilities depending on the requirements. For on-farm grain storage, it is important to control and monitor the key factors such as pests, temperature, humidity, etc…, which may lead to loss of grains. The best time to plan all the requirements for grain storage is the harvest time so that we can identify issues and figure out opportunities for the future. Unfortunately, many of these grains are lost due to lack of quality management and pests, insects.

Silos are considered to be the most common method of all grain storing facilities available nationally. These silos have a variety of configurations such as flat-bottom, cone base, sealed, non-sealed and non-aerated. They require huge capital investment as they are permanently fixed once constructed.

                                       fig 1: Silos for grain storage.                              source (link1)

Once the silos are in-loaded with the grains, we need a system to monitor and control the temperature, humidity, pressure, moisture, and the threat from pests. This is the point where technology comes into act. We need a system that can monitor all the parameters and reduce or eliminate the grain loss. Or else due to moisture reasons and pests, we lose many grains. So, there are many ways in which one can make an automated system to control the issues. These systems should be highly reliable, effective, consume low power, cost-effective. There are many ways to develop a real-time monitoring and control system that uses necessary hardware and software.

Hardware devices and software methods together help to create a system that can make sure the quality of grains which are produced and stored for human consumption have good quality and are safe from all the affecting factors.

Technologies that can be preferred to monitor the parameters are:

  • SCADA system
  • ZigBee wireless sensor network (WSN)
  • LabVIEW
  • Cyber-Physical Systems which uses WSN

All these above-mentioned systems can be used to monitor the data which is an output form the various sensors which are equipped in the grain silos. These systems can be used to monitor the data continuously so that they can quickly react to any of the changes.

SCADA system: It is an advanced system that can monitor and control the applications which are technically running on a PC. This system deals with both hardware and software applications. The data which is the output of any hardware device is transmitted to the PC by the server. The software in the PC makes use of the data and give us accurate results. SCADA uses data acquisition card (DAQ) to connect to all the hardware elements. Monitoring and controlling the data is the key role of a SCADA system. Nowadays SCADA has advanced in many fields such as engineering, medical, nuclear field, and industries.

Wireless Sensor Networks: It is a sensor network that is developed by installing various sensors. It consists of a station and number of nodes (sensors). These networks are basically used to measure temperature, pressure, sound and then pass the data to the main server or the central processing node. WSN is used to monitor and control the process and is spread across many fields such as military applications, health monitoring, etc…

LabVIEW:It is a programming workbench that is used to create programs in graphical notations. It offers hardware integration so that we can optimize the hardware. LabVIEW real-time module is used to create and distribute system applications for testing, monitoring, and control. This is the advantage of a real-time system because it ensures reliability and timing. There are many LabVIEW libraries which are used for data acquisition.

Temperature and Humidity sensors to be used:

  • SHT20 I2C: It is a temperature and humidity sensor which is equipped with a dual waterproof protection probe. This contains an amplifier, an A/D converter, a digital processing unit (DPU) and an OTP memory. It shows long term stability and is reliable. It can precisely measure relative humidity and temperature of the environment. There is also a Pull-up resistor of 10K and a filter capacitor of 0.1uf, which enables the sensor to directly use with Arduino.
  • SHT25 I2C: This provides high accuracy in terms of intelligence, linearized sensor signals. Even this is reliable and long-term stable. This can be plugged into the Arduino interface directly.


Long Range Sensor (LoRa): This is a long-range sensor and LoRa technology is a wireless radio frequency technology which is a long-range, low power platform which became a technology for the Internet of Things (IoT). It enables smart IoT applications that solve many problems. It can easily plug into available infrastructure which enables low-cost battery-operated IoT applications. It is called the DNA of IoT.


Pressure sensors:

  • MPL115A2: It is a pressure/temperature sensor which is said to be a low-cost sensor used to measure barometric pressure. Low barometric pressure means low-pressure trough, warm air rises cool down as it goes higher into the atmosphere. If the barometric pressure seems to be increasing rapidly it is said to have high barometric pressure. Barometric pressure is measured in inches of mercury or in Hg. This sensor is to be soldered on a PCB board with 10K pull-up resistors on the I2C pins.


Still, at many of the storage farms, people are using the manual aeration systems in which the operator has to go and note down the temperature and humidity details from time to time. Everything is going on manual at many of the places even though the technology is advancing day by day. The benefit of automatic systems is there would be no errors due to human intervention and the job becomes more efficient and saves time. This automatic system should be energy-efficient and more accurate.

In this paper, I am working on developing a sensor spear that can go into the grain silos and log the data every 2 minutes using various sensors and finally view the data either locally through a Bluetooth phone or via the internet using LoRa (Long Range Sensor).


Literature review


In this paper, their sole purpose is to develop a monitoring and controlling system for grain storage. They used the cost-effective ZigBee wireless sensor network which uses less power, programmable, networking, supervisory and extendable. As a part of this network, there are three devices namely coordinator (FFD), end device (RFD) and a router (FFD). Where the end device is a reduced-function device and rests two are fully-functioned devices. This network consists of ZigBee nodes which are used to collect the local temp, wind pressure and moisture, to route data between the nodes or to receive information. This information is then transferred to the control system, which is running on PC, uses the RS232 interface (serial communication). This data is then viewed and monitored accordingly. Apart from its being less power consumptive and cost-effective, ZigBee is the best in the short-range wireless communication field. This is the reason they used a number of nodes to extend the network in order to collect the information. They can moreover use some long-range sensors which reduce the complexity in the hardware part and also organize a wireless network for routing dynamics. To conclude, in the process of installation and maintenance, ZigBee systems show better efficiencies, cost and time (Zhou et al., 2009).

The authors of this paper focus on the silo management system which is monitored by a SCADA system. And they also discussed the aeration process inside the grain storage system. They designed an aerated system that makes use of 4 elements such as, airflow rate, air distribution, fan selection, ventilation system. These are the 4 factors that they considered to bey the key factors while making a silo management system. As we know that grain losses are due to temperature, humidity and pressure variation inside the silo, they developed a system in which, when the temperature is high, the fan is switched on and the air circulation takes place and the vent is opened simultaneously so that the heat from the grain flows out through the cold air. Whereas, when the temperature is low, the vent closes again while the fan is switched off. The data is controlled and monitored using the DAQ card (Data Acquisition Card) which changes the signal from analog to digital, which passes on to the PC and the process goes on. They may face issues due to dust, rain when the vent is open, but this system makes the work more effective and easier when compared to the manual method of monitoring silos (Zakaria et al., 2009).

This paper came up with a solution to get rid of an insect called as Coleoptera, Bostrichidae by controlling the temperature in a grain silo prototype. They basically used a bin contained insects of R. Dominica in wheat grain. The prototype consists of 3 fans that blow cool air inside the bin and placed 2 temperature sensors at two different positions, depths in the bin. The cold air is drained through 3 different inlets, crosses corresponding heating resistances. The hot air now acts on the wheat grains stored in the bin, changing their temperature. The controllers interpret this information to regulate the energy sent to discard impurities and hot air. Where T1 and T2 measure instantaneous temperature readings from the grains. Each controller implements a proportional integrative derivative (PID). It is a two-input two-output control system with few reference points of temperatures 35, 47.5, 60 degrees and reference timings of 24, 72 and 120 hours. It is observed that there is a 100% mortality rate of insects at temperatures 47.5 and 60 degrees in all exposure times whereas, it’s not similar in the rest of the cases for low temperatures. But the fact that increasing the temperature can damage the grain even though it gets rid of the insect is not given any importance (De Souza et al., 2013). Another way can be by implementing the technology which absorbs oxygen and avoids wastage of grains due to pests.

This study is to develop a smart system that helps for efficient monitoring of grain storage. To avoid the loss of grains due to pests, external factors the authors of this paper adopted smart solutions to optimize such storage conditions where we can efficiently monitor the quality of grains so that, they last for a longer periods. They used the potentials of Cyber-Physical Systems (CPS) which is an integration of computing, communication systems to sensors and actuators.

A wireless sensor network (WSN) is deployed in the grain storage bin to sense various parameters such as pressure, temperature, and humidity. This data is sent to the cloud and the control measures are applied. They also used the concept of inter nodal path (INP) to avoid the overhead due to more sensors. INP uses node-to-node communication between nodes in the network. INP and cluster heads are inversely proportional to each other which either way increases the cost, as power consumption is based on cluster heads. So, they adopted a way to find max-min hop counts. Now, the central processing nodes receive all the data and it passes to the management unit which takes care of the quality of the grain. This work by them is something interesting as it got some physics in it and is different from a lot of studies based on

monitoring of grain storage (Parvin et al., 2018).

There are countries with a humid and tropical climate which lack in the drying technology of grains. So, in order to overcome these types of issues, it’s better to come up with a system that can control temperature, humidity and pressure conditions in the grain silos. A study by John M. Fielke and Chandra B. Singh came up with the ways to get rid of grain loss due to insects and factors such as temperature, humidity, and pressure. It is said that continuous monitoring of the parameters is needed. It is also said that storing grains at high temperatures and moistures have a lesser life due to an increase in self-heating, metabolic activities, rate of respiration, etc…

This study mentions something interesting about the in-silo drying and aeration system. Some threshold values of moisture contents are taken, and the dynamic in-silo grains moisture is continuously monitored. And the number of insects can be reduced or avoided by providing required dosages of phosphine or providing unfavorable conditions for insect growth. The temperature, humidity sensor cables are used, and the oven-dry method is used for monitoring the moisture of grain. These are some developments in grain silos monitoring and control which is cost-effective, efficient (Singh et al., 2017).

These are the various ways and related works to monitor and control the grain silos so that the loss of grains is reduced or eliminated.













Research design:




My research design includes the problem identification, what to work on, research questions to be answered, collect the information needed from papers, articles, etc… gather the information at one place, get the key points which help me in my research plan, develop the plan by reviewing the data collected, graphically draw the prototype of what the actual plan is, finding out suitable ways to proceed with the work such as the software needed, components required as per the process, and then further format the data, perform, obtain the results, further analysis of the results then concluding and mention any future developments which can be done.





Planning throughout the research is important before starting it. Creating it helps us proceed with the work and one will know what to achieve in the end.

1. Problem identification: Firstly, after selecting the topic for my thesis, I identified the particular problem to work on. I started working on the development of a sensor spear to a grain silo and monitor the data continuously for every 2 minutes, at the same view the data in real-time by internet using a long-range sensor.

2. Identified parameters to work on: I decided to work on monitoring the temperature, humidity and pressure factors of the grain silos as these are the key factors that lead to the loss of grains because of dynamic changes. Now the step is to draw the prototype model of the grain silos with the sensors.

3. Prototype:



This is the prototype or a diagrammatical representation of grain silo in which RH/temp sensor is sent inside through the orifice and planned to place a pressure sensor whose one nob in inside the grain silo while the other one is outside, this is so because to compare and maintain the inside and outside pressure. And a fan is for aeration purpose to maintain temperature, humidity inside the silo.

4. How to log data: To log and monitor the data from the sensors I planned to interface them with ESP32 Arduino. This plays a key role in monitoring the data continuously for every 2 minutes. And to view the data online I planned to use a long-range sensor called LoRa and this technology is called LoRa technology.

5. Sensors: To make sure that this system is cost-effective and reliable I decided to use SHT20, SHT25 I2C for temperature/humidity sensing, and MPL115A2 for pressure sensing.

6. Made a note of sensor specifications:



Voltage (Vin)

2.4 to 5.5 VDC

Sensing range

500-1150 hPa (up to 10km alt)

Altitude resolution

1.5 hPa/50 m

Addressing mode

I2C 7-bit address 0x60

Logical i/p

3 to 5V


Operating voltage

3.3 to 5V

RH response time



+-3% RH/+-0.3 degree C


0 to 100% RH/-40 to 0125 degrees C

Communication interface


7. ESP32: I am working on a Heltec automated ESP32 module, to which we can setup Arduino IDE. This is a module that integrates Wi-Fi, and OLED display on top of it.

Features: 240 MHz processor speed, 4 MB flash memory.

Pin specifications of ESP32:

fig 2: pin diagram of ESP32.

After studying about what ESP32 offers I planned to add deep-sleep mode to it. I planned to set up ESP32 with Arduino IDE, LoRa into a deep-sleep mode and measure the power consumption of the system. Also, I came to know that there are different ways to wake it up, such as touch wake up, timer wakes up and external wake up.

8. Why I preferred deep sleep mode?


Because there is no point in running my ESP32 on active mode with batteries on since the power from the batteries drains up quickly. Whereas, in the deep-sleep mode, it reduces the power consumption and batteries last longer. It wakes up the processor when something which is interesting happens. In deep-sleep mode, only RTC (Real-time Clock) peripherals and ULP (Ultra Low Power) co-processor are turned on.

ULP co-processors: This processor does analog-digital conversions (ADC) and at the same time level the thresholds while in deep-sleep mode.


fig 3: Heltec automated ESP32.


It has 36 pins in which 3 pins are ground (GND), 4 pins for power (5V, 3V3 two each), one reset pin, one pin to transmit and one to receive data. Whereas, the other 26 pins are control pins, touch pins, GPIO port pins, DAC (Digital Analog conversion pins), serial ports for serial communication, and some on-board hardware pins to connect for OLED display.

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9. Content: Meanwhile gathered the content for literature writing from related works. Went through some IEEE papers related to my thesis work, analyzed all the work given in those papers. I made some notes from those papers which I think would help me out in my work. Compared to various papers, new technologies used, the invention made and question to self, what can be done to further improve the system and make it more reliable and efficient. Some of the studies mentioned the use of short-range sensors and spreading the network which then faced overheads so, I gave a thought to me why not use a long-range sensor which is more efficient to work on and can also view the data wirelessly. There are many questions raised while going through all the studies that were once published and tried to answer them.

10. Research plan: Once I went through the papers and prepared the literature review content, I then started writing my research plan which includes aim, objectives and a detail introduction of how the problem is raised and end it up saying what I am going to do in my research.

11. Prepared Gantt Charts for minor thesis 1 mentioning all the work I have done all these days and also prepared a chart for the thesis work to be done in the future. At the end of this thesis 1, I am familiar with all the components I am using in my research, their specifications, features, modes in ESP32, how to interface sensors with Arduino and how to set up Arduino IDE to ESP32. Also, been through the basics of coding for the SHT20 RH/temp sensor.



Minor thesis-1: It all started from choosing the mentor and selection of the topic to work on. Once the topic is decided, I worked on problem identification where many questions raised like what particular path to follow. Then I started browsing the related work from web pages, IEEE papers, journals, through which I gathered a lot of information. I then started to get into detail by choosing what particular hardware and software I should use throughout my thesis. I made a research plan and design which includes steps to follow. Then assembled all the data together and analyzed it. Once I am finalized with using the mentioned hardware components such as temperature, humidity sensors, and pressure sensors, I started getting familiar with the specification of those sensors and particularly in case of ESP32 Arduino, I took more time to study its specification, various modes of operation, set up of Arduino IDE with ESP32 and use of LoRa sensor for long-range sensing, learned about deep-sleep mode. And then, I came to know a bit about the coding of RH/temp SHT20 sensor while interfacing with Arduino. Then, I started literature writing and started making my final report.


Minor thesis-2: The first thing I need to do is get the rest of the components which are needed other than the ones which I have now. Second of all start working on the coding part of ESP32 and SHT20 RH/temp sensor. Have to make a prototype model of the grain silo. Start interfacing sensors with ESP32 module and set up Arduino IDE with ESP32 and interface LoRa. We should look at the deep sleep mode coding in-depth for the required project deliverables. It’s basically more of a software part which is to be connected to the hardware implementation of grain silos. Then analyze the outputs, results, try to improve and make the system more efficient so that the project deliverables are achieved. Then finally make the required reports and presentations for the final submission.









Gantt chart for minor thesis-1:


fig 3: Gant chart for minor thesis-1.

Gantt chart for minor thesis-2:


fig 4: Gantt chart for minor thesis-2.







1. The aim is to develop a sensor spear which is more efficient and reliable.

2. Also, it is expected that the system consumes less power due to the deep-sleep mode in ESP32.

3. The reason for doing this project is to continuously monitor and control the system.

4. By, interfacing various other sensors to ESP32 one can log the data continuously which depends upon the time set while coding.

5. The main purpose is to view the data time-to-time which can be done locally or through the internet.

In this project, I use a long-range sensor LoRa which is wireless communication technology.

6. Long-range sensing, a system in deep-sleep mode, less power consumption and automatic control of temperature, humidity, the pressure inside the grain silos are the expected outcomes from this project.




  1. Huiling Zhou, Fengying Zhang, Jingyun Liu, and Fenghui Zhang, A Real-time Monitoring and Controlling System for Grain Storage with ZigBee Sensor Network, 978-1-4244-3693-4/09 IEEE 2009.
  2. Nuraishah Binti Zakaria, Irraivan Elamvazuthi, Noor Hazrin Hany Binti Mohd Hanif, Silo Management System, Proceedings of 2009 IEEE Student Conference on Research and Development (SCOReD 2009), 16-18 Nov. 2009, UPM Serdang, Malaysia.
  3. Denis W. F. De Souza, Alessandro N. Vargas, Jo˜ao B. R. do Val, Adriana M. Freitas, and Irineu Lorini, Control of temperature to suppress the population of Rhyzopertha Dominica (F.) (Coleoptera, Bostrichidae) in a grain silo prototype, European Control Conference (ECC), July 17-19, 2013, Zürich, Switzerland.
  4. Sazia Parvin, Amjad Gawanmeh, Sitalakshmi Venkatraman, OptimisedSensor-Basedd Smart System for Efficient Monitoring of Grain Storage, 978-1-5386-4328-0/18 IEEE 2018.
  5. Chandra B. Singh and John M. Fielke, Recent Developments in Stored Grain Sensors, Monitoring and Management Technology, IEEE Instrumentation & Measurement Magazine, 1094-6969/17, 2017.
  6. Z. Hao, Y. Zhao, Y. Cao, D. Li, T. Zhen, P. F,  and J. Wu, “Basic statistical characteristics ofthe  spatial and temporal distribution of temperature in the cube grain warehouse”, Grain Storage Technology,vol. 39, no. 4, pp. 15–20, 2010.
  7. Raul Morais, Miguel A. Fernandes, computers and electronics in agriculture 6 2 ( 2 0 0 8 ) 94–106 ,A ZigBee multi-powered wireless acquisition device for remote sensing applications in precision viticulture.




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