1. Honeybee Temperature Monitor and Control
ECE 110 Honors Project
by
Evan Qi, Anshil Bhansali, and Yining Wang
UID: eqi2, abhansa2, ywang308
12/10/2014
1 | PAGE

2. Table of contents
I. Introduction ………………………………………………………… 3
Problem description ……………………………………………………………… 3
Design Concept …………………………………………………………………… 3
Materials …………………………………………………………………………. 4
II. Analysis of Components ….………………………………………… 5
Characteristics of Sensors ………………………………………………………… 5
Design Considerations …………………………………………………………… 5
III. Design Description ………………………………………………… 6
Block Diagram …………………………………………………………………… 6
Circuit Schematic ……………………………………………………………….… 6
Arduino Programming …………………………………………………………… 8
Physical/Mechanical Construction …………………………………………………
9
IV. Conclusion …………………………………………………………. 10
Lessons Learned ….……………………………………………………………… 10
Self Assessment ……………………………………………………………………
10
2 | PAGE

3. I. Introduction
● Problem Description
During the winter, honey bees huddle together and flutter their wings to generate heat. Some
bees also die because of the cold. To prevent that, we built a device that senses and records the
surrounding temperature in the hive, and sends a signal to turn on an infrared bulb, using
negative feedback to maintain the air temperatures at a certain level.
● Design Concept
In the design, a powered TMP36 temperature sensor is put inside the honeybee hive. This sensor
measures the temperature of the air within the hive and varies its output voltage depending on the
the surrounding temperature. This output voltage is then read by the Arduino and converted into
Celsius degrees. If the temperature is below a certain threshold, 30 degrees Celsius, the Arduino
sends an analog signal to a transistor, which then acts as a switch to allow current through a heat
bulb. When the sensor measures a temperature below 20 degrees Celsius, the bulb receives full
power. As the temperature decreases from 30 degrees to 20 degrees Celsius, the power to the
bulb increases linearly. In this design, an LED is used instead of a heat bulb, as a
proof­of­concept.
TMP36 Measurement (Celsius) Heat Bulb Power (% Maximum)
>=30 degrees 0 (Off)
30 degrees to 20 degrees 0 to 100
<20 degrees 100
Table 1: Truth Table for Temperature and Bulb Power
3 | PAGE

4.
● Materials
Item Quantity
330 Ohm Resistor 3
LED 1
TMP36 Sensor 1
P2N2222A Transistor 1
Table 2: Items Needed for this Project
4 | PAGE

5. II. Analysis of Components
● Characteristics of Sensors
The temperature sensor measures from ­40 degrees Celsius to 125 degrees Celsius. Since the
only temperatures we are concerned about are between 20 and 30 degrees, we only measured the
output voltages at these temperatures. To measure the output voltages, we hooked the sensor up
to the Arduino and read the outputs at these two temperatures. Then we used an equation to
convert these numbers into voltages.
Temperature (Celsius) Analog Input to Arduino Voltage (Volt)
20 degrees 143.36 .7
30 degrees 163.84 .8
Table 3: Outputs and Voltages of Sensor at Key Temperatures
● Design Considerations
Originally, we had planned to put multiple sensors in the beehive to create a temperature
gradient. However, we had neither the time nor the resources to do so. In the end, since we only
had one sensor, we decided to put it in the middle of the hive, towards the bottom. This decision
was based on the fact that hot air rises, thus making the bottom of the hive cooler than the top.
Since the ideal temperature for the beehive is between 30 degrees and 35 degrees Celsius, and
the temperature threshold for our programming is at 30 degrees, the best location to place the
sensor is in the cooler part of the hive.
Another point to consider is the fact that honeybees will coat the temperature sensor with hive
material. This may affect the temperature readings slightly, but not to the point where the device
will no longer function. Since the material is on the inside of the hive, the outside temperature
will have negligible effect on the sensor, and the sensor will still read internal temperature.
5 | PAGE

6. III. Design Descriptions
● Block Diagram
Figure 1: Block Diagram of Design
● Circuit Schematics
Figure 2: Circuit Schematics of Design
6 | PAGE

7. ○ Temperature Sensor Sub­circuit
The temperature sensor sub­circuit consists of a temperature sensor (TMP36), which
measures the temperature at its surrounding environment and provides a voltage output to
the Arduino, and a 330 ohm resistor which protects the TMP36 from high voltage. We
connect these two components to the 5 volts voltage and connect the output of TMP36 to
the A0 on the Arduino. The output voltage will act linearly proportional to the
temperature, meaning a higher temperature will result in a higher voltage output.
○ Bulb Sub­circuit
The bulb sub­circuit consists of a single transistor. The transistor reads the PWM of the
signal from the Arduino through its base and then transmits that same PWM to the
collector and emitter. The duty cycle of the PWM determines how often the bulb is on,
and thus how bright it is. In this design, we used an LED powered by a 5 volt voltage
source; however, the actual device should utilize a 250W/120V heat bulb plugged into a
120V wall socket. Since the current used to power the bulb would be higher than to
power the LED, a transistor with a higher multiplier value would likely be used.
7 | PAGE

8. ● Arduino Programming
const int temperaturePin = 0;
const int outputPin = 9;
float voltage, degreesC, degreesF;
int count;
void setup()
{
Serial.begin(9600);
}
void loop()
{
voltage = getVoltage(temperaturePin);
degreesC = (voltage ­ 0.5) * 100.0;
degreesF = degreesC * (9.0/5.0) + 32.0;
Serial.print("nVoltage: ");
Serial.print(voltage);
Serial.print(" C: ");
Serial.print(degreesC);
Serial.print(" F: ");
Serial.print(degreesF);
output(degreesC);
count+=1;
if(count=50/*every 5 seconds*/)
{
/*write to SD card*/
count=0;
}
delay(100)/*reads every .1 seconds*/;
}
float getVoltage(int pin)
{
return (analogRead(pin) * 0.004882814);
}
void output(float degree)
{
if(degree<30&&degree>=20)
{
analogWrite(outputPin,12/*(164­analogRead(temperaturePin)));
}
else if(degree<20)
{
analogWrite(outputPin,255);
}
}
The purpose of the Arduino code is to read the output of the TMP36 sensor. Then, it takes the
output value and puts it in an equation to determine the duty cycle of the PWM it outputs. The
Arduino output increases linearly as the TMP36 sensor’s output increases, so that the PWM
reaches 100% duty cycle at 20 degrees Celsius.
8 | PAGE

9. ● Physical/Mechanical Construction
Since this project was simply a proof­of­concept, the device was not actually built. The idea is to
attach the temperature sensor to the bottom of the beehive, where the air is cooler. A small hole
may be drilled into the bottom of the hive to feed wires through to an Arduino beneath the hive.
The Arduino processes the information inputted from the sensor and records it to an SD card.
Then, depending on the temperature of the hive, the Arduino feeds an analog signal to the
transistor, and in turn, the heat bulb. The bulb should be placed towards the bottom of the hive,
so that the heat dissipates upwards, heating the entire hive. Although the sensor, the Arduino,
and the heat bulb could be compacted into a single item, the item will likely be too large to fit
into the beehive without disturbing the bees, and thus should be kept in its individual parts.
9 | PAGE

10. IV. Conclusion
● Lessons Learned
Originally, we had planned to use a different temperature sensor, the TMP006, to measure the
temperature. However, once we learned how the sensor worked, we decided that it was not ideal
for our device. The TMP006 reads the infrared emissions of the object it is pointed at and
determines the temperature from that. Since our device was designed for a hive full of live,
working bees, we figured that the bees may interfere with the signal, and instead of measuring
the ambient air temperature, the TMP006 sensor may measure the body temperature of the bees.
In the end, we decided that a better sensor to use would be the TMP36, which reads the
surrounding temperature, instead of the TMP006, which reads infrared emission.
● Self­Assessment
The honeybee temperature monitor and control system performed as we expected in the truth
table. When we decrease the temperature around the temperature sensor, the LED in the bulb
sub­circuit flashes more frequently than before, which means that our bulb will add more heat to
the beehive when the temperature is cooling down. The device functions as planned, and given
the time restraints, the team did a good job in creating a fully­functioning device.
10 | PAGE