WIXLIB

3.4 XBEE Pro RadioFor the communication between Transmitter and Receiver, XBE Pro Radios are used. This isbecause it has the radios have an outdoor/RF Line-of-Sight Range Int’l 5000 ft (1500 m), serialData Rate 1200 bps - 1 Mbps, fast 250 kbps RF data rate to the end node, 2.4 GHz forworldwide deployment, sleep modes supported for extended battery life.3.5 Graphic LCDFor displaying the data at the receiver end, graphical LCD KS0108 (128X64) is used. This isbecause, it allows full graphical control compared to a regular 16x2 LCD. Also, it suits theproject requirement of showing the data graphically at the receiver. It is the most commonlyused graphical LCD and has good online support for header files and user manuals on how touse it. It also has a low power white LED back-light to help the user view the screen clearly.3.6 Solar PanelThe Solar panel used in the project is a 2 Watt, 12V battery maintainer panel. As the batterybeing used in the project is a 12V battery, it serves the purpose. It can easily be connected anddisconnected to the battery. No direct sunlight is needed and the panel works even in cloudyconditions. It is overcharge and discharge protected. Also, it is lightweight and compact indesign. It provides a voltage between 16 and 23 Volts DC in full sun.3.7 BatteryThe battery used in the project is a 12V 7AH battery. It is sealed and maintenance-free. Thebattery has a long service life; under normal operating conditions it works five to six years instandby applications or between 200 and 1000 charge/discharge cycles depending upon depth ofdischarge. It is resistant to shock, vibration, chemicals, and heat. It is compact. It operates over atemperature range of -76 F to 140 F. All these features make it very suitable for the project.Beehive Temperature and Sound MonitorPage 10

4DESIGN4.1 ApproachThe project is divided into two parts: The Transmitter Circuit and The Receiver Circuit.The data flow of the project is linear. First, the temperature and sound intensity information isread from the sensors. The data is then fed to two separate ADC (Analog to Digital Converter)channels in the transmitter MCU which samples the signals at 8KHz and converts them intodigital signals. Then, the digital data is converted back to meaningful information and istransmitted to the Transmitter XBEE Pro Radio through USART. The Transmitter radiotransmits the information to the Receiver XBEE Pro Radio in the form of packets using wirelesscommunication. The Receiver radio receives the packets and then sends this information to theReceiver MCU using USART. The Receiver MCU analyses the data and displays it on thegraphical LCD interfaced to it.The flow is shown in the below block diagram.Figure 1 Block Diagram4.2 HardwareThe hardware is split into two main parts: The Transmitter Circuit and the Receiver Circuit.Both these circuits are explained in detail in this section.4.2.1Beehive TransmitterBeehive transmitter circuit is responsible for reading and transmitting hive conditions. Itsschematic diagram is below.Beehive Temperature and Sound MonitorPage 11

Fig 2: Schematic Diagram for Beehive Transmitter CircuitThe Transmitter circuit mainly consists of Transmitter MCU, Temperature sensor, Acousticsmeasuring circuitry, Transmitter radio.Once built and tested, I built a PCB for the transmitter using EAGLE software. Then I orderedthe printing of PCB online at Advanced Circuits (4pcb.com) by uploading necessary gerberfiles. Refer to “Appendix E” for detailed information on PCB Transmitter board details.4.2.1.1 Transmitter MCU (ATmega 1284P)The transmitter MCU is responsible for reading the information from the sensors, operating onthe information read, transform the same to user understandable information and transmitting itthrough USART to Transmitter XBEE radio. This MCU has a temperature sensor, electretmicrophone, operational amplifier, and a XBEE Radio (Transmitter Radio) interfaced to it. TheMCU uses specific algorithm to transmit the information. This is explained in detail in thesoftware section below.4.2.1.2 Temperature Sensor (LM34DZ)The temperature sensor should be capable of measuring a wide range of temperatures. In theproject, LM34DZ is used to measure the temperature in the beehive. It is calibrated directly in F and measures from -50 to 300 F.Below is the diagram of LM34DZ. It has 3 pins: Ground, Power supply and Vout. The Vout pinis connected to ADC channel 7. The temperature sensor reads the temperature and passes it onto the MCU (A7). MCU translates the value to corresponding Fahrenheit value and transmits thesame.Beehive Temperature and Sound MonitorPage 12

Figure 2 LM34DZBeehive Temperature RequirementAs honey bees are social insects, a honeybee colony can survive when the temperature of theexternal environment is between -4 and 118 ºF. However, they show the best performance atthe temperatures between 70 and 95ºF. When the temperature falls below 57ºF, thehoneybee starts not leaving the hive and forming a ball (winter cluster). When the temperaturefalls below 43 ºF, the hive has the appearance of an exact ball. It is known that each bee canproduce a heat of 0.1 calorie per minute at 50ºF. Also, depending on various activities going oninside a beehive, the temperature varies widely. For example, when the temperature drops to 57 F, the bees begin to form a tight cluster. Within this cluster the brood (consisting of eggs, larvae,and pupae) is kept warm-about 93 F – with heat generated by the bees. However, most of thetimes, the beehive temperature will be in the range of 60 F to 100 F.4.2.1.3 Acoustics Measuring CircuitryIn a beehive, the typical frequency range of the sound will be between 180Hz and 260Hz. So,the acoustic measuring circuitry i.e., the sound sensor built should be able to operate in thisband of frequency. The circuitry is shown in the Schematic diagram above.The audio amplifier circuit accepts a microphone audio input signal. The signal is fed intoLM358 op-amp. A 2nd order low-pass filter with a cutoff frequency at 500Hz and a high passfilter with a cutoff frequency at 50Hz are built using the op-amp. The filtered signal is then fedto the ADC through a 330Ω resistor.Since the ADC cannot read negative voltages, a bias voltage of 2.5V is chosen so that it sitsbetween 0V and Vcc. To achieve this bias, the input from the microphone is DC-biased to 2.5Vwith two 100kΩ resistors and a 68nF capacitor. The resulting biased signal is then amplifiedthrough a non-inverting amplifier circuit with high-pass cutoff frequency at 50Hz. The highpass cutoff frequency was chosen such that the DC bias voltage would not be amplified by thenon-inverting amplifier. This is also the reason for choosing the specific value for the capacitorat the biasing stage, since the high-pass cutoff frequency of the level-shifter should match withthat of the amplifier circuit.The mic-in circuit runs the input from the microphone through the biasing circuit. This signal isthen passed through a non-inverting amplifier with a 2MΩ resistor on the negative feedbackloop. This value was chosen after experimentally determining the maximum voltage swing ofBeehive Temperature and Sound MonitorPage 13

the mic-in signal to be around 20mV peak-to-peak. Thus, to be able to detect sounds ofreasonable strength and distance away from the microphone, the above resistor value is chosento obtain a gain of 133.33V/V, or 42.4 dB. This ensures that the maximum output of themicrophone results in a full voltage swing across the ADC range.Since the audio signal is sampled with the ADC at 8 KHz sampling rate, it must be low-passfiltered before the ADC conversion to remove aliasing. A 2nd-order Sallen-Key low-pass filteris built using the op-amp with a cutoff frequency of 500Hz.4.1.1.1 XBEE Pro Radio & AdaptorAn XBEE Pro radio is installed at the transmitter which is used for transmitting the temperatureand sound information read and transformed by the MCU. XBEE Pro has a UART interface andcan connect directly to a microcontroller. Using UART, the radio can be used to communicatebetween microcontroller to microcontroller or between PC to microcontroller. XBee Pro radio isdesigned for 3.3V system. So, in order to interface the radio with ATmega 1284p MCU, anadaptor kit is used.XBEERxTx5VGndFig 4. XBEE Radio with adaptorMCUTxRx5VGndTable1: XBEE and MCU ConnectionsThe adaptor can be used to interface for 5V microcontroller board. The XBEE radio can beconnected to either a PC or MCU using this adaptor. The radio is mounted on top of the adaptorkit as shown in figure 8. This connection is used to configure the radio which is explained indetail in the software section. Once the radios are configured, then they are connected to theMCU using headers. The connections between the radio and the USART of the MCU are shownin the above table.Once the radios are configured and the hardware is set up as explained above, one can transmitand receive data using the radios. A XBEE Pro radio could be configured in differentconfiguration depending on the network topology. Various network topologies are explained indetail in the Appendix section of this report4.2.2Beehive ReceiverBeehive Temperature and Sound MonitorPage 14

Beehive receiver circuit is responsible for receiving the transmitted values from the transmitter usingXBEE, analyze the received values and display them on an LCD.The schematic diagram of the receiver circuit is shown below.Fig 5. Schematic Diagram of Beehive Receiver CircuitThe A0, C0 etc pins represent the port pins on the MCU.Once built and tested, I built a PCB for the receiver using EAGLE software. Refer to “AppendixE” for detailed information on PCB Receiver board details.4.2.2.1 Receiver MCU (ATMega 1284P)The Receiver MCU is responsible for the reception of the data and data display. This MCU hasan XBEE Radio (Receiver Radio) and a graphic LCD interfaced to it.4.2.2.2 XBEE Pro RadioAn XBEE Pro radio is installed at the Receiver which receives the temperature and soundinformation transmitted by the transmitter through XigBee protocol.4.2.2.3 Graphic LCDKS0105 graphic LCD is used for displaying the temperature and sound information. It has ablue background with 128 x 64 'monochrome' white pixels. For the contrast adjustment, a 10Kcontrast pot is used. The pin description and MCU connections are explained in detail in thetable below. The connections are shown in the picture below.Figure 3 Receiver MCU Connected to Graphic LCDPINSYMBOL FUNCTIONBeehive Temperature and Sound MonitorMCU PINPage 15

5GroundPower supply ( 5 V)Contrast adjustmentData/instructionData read/writeH L enable signalData bus lineData bus lineData bus lineData bus lineData bus lineData bus 920DB6DB7CS1CS2RSTVEEAKData bus lineData bus lineChip select for IC1Chip select for IC2ResetNegative voltage outputPower supply for LED ( 4.2 V), RA 0 ΩPower supply for LED (0 V)PC6PC7PA0PA1VCCVCCGNDTable 1 KS0108 Pin Description and MCU Connections4.2.3PCB boardsThe resulting circuits (both transmitter and receiver) are then4.3 SOFTWAREThe software portion is split into two independent project modules i.e. one for the TransmitterMCU and the other for the Receiver MCU.4.3.1Beehive TransmitterThe transmitter MCU is responsible for the data acquisition, converting the analog data signalinto digital signal by ADC sampling and transmitting the processed data to transmitter Radiothrough USART.4.3.1.1 ADC SamplingThe temperature data and modified audio signal from the audio analog circuit was fed into theADC port A.7 and A.3 respectively. The DC bias voltage was fed into A.1. The ADC voltagereference was set to AVCC. By default, the successive approximation circuitry requires an inputclock frequency between 50kHz and 200kHz to get maximum resolution (according to theAtmel Mega1284 specifications). The ADC is set to run at 125 kHz and it takes 13 ADC cyclesBeehive Temperature and Sound MonitorPage 16

to produce a new 10-bit ADC value (ranging from 0-1023), or about 104us. Since 10-bit ADCresult is used, the ADLAR in ADC was set to zero.4

2.2.1 Bee Hive Temperature and Sound Monitoring System (BHTSM) This section lists the requirements to be met by the Beehive temperature and sound monitoring system (BHTSM). [SYS-01] The BHTSM system shall include Transmitter module to relay temperature and sound Note: The requirements for the Beehive Transmitter are listed in Section 2.2