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Step 6Electronics
Circuit Overview
Project Big Bird required two circuits, each with specialized functions:
Onboard PIC circuit:
send/receive data from host PIC via wireless
controls the lift fan and propulsion fans via PWM output signals
reads sensors (convert analog to digital)
Host PIC circuit:
send/receive data from host computer via USB
send/receive data with host PIC via wireless
Photos of both are shown below.
Circuit Diagrams also appear below
Power
Onboard:
Takes in +6V from Novak Electronic Speed Control (ESC) Power Output
Runs entirely on +3.3V, produced by a voltage regulator
Host:
Runs on +5V from host computer
XBee module uses +3.3V, produced by a voltage regulator
Microcontrollers (PICs)
We choose to utilize microcontrollers from the Microchip Technology’s PIC18F family due to availability and our previous experience. The data sheet for this class of microcontrollers can be found here.
Electronically, these PICs require between 2.5-5.5 V, well within the range of both circuits.
Wireless Module
To achieve wireless data transfer between the host computer and the onboard lift and propulsion fans, we chose to use a XBee Pro OEM RF Module, as shown below
The XBee provides a low cost, low power solution to the wireless communication. It offers a 300 ft range over a standard 802.11 frequency. The device is ready to operate right out of the box with minimal support circuitry. A pin diagram is shown below
Pins 1 and 10 must be connected to +3.3V and GND, respectively. Pin 2, the XBee’s data output node, connects to pin 18 of each PIC. Similarly, pin 3, the XBee data input, hooks in to PIC pin 17. These four connections are all that is necessary to send and receive byte data wirelessly between PICs.
For more information on the XBee OED RF module, check out the manufacturer data sheet.
Lift Fan Electronics
Big Bird’s lift fan is a Novak GTB/SS 10.5 Pro Brushless System, which includes the motor, the speed control, and other necessary components.
This system requires 4.8-7.2 V to run, which motor performance increasing as the input voltage approaches 7.2 V.
The lift fan system’s electronic speed control (ESC) provides a +6V power output alongside the white signal cable which provides PWM control of the lift fan. This +6V was down-regulated to +3.3V and used to power the onboard circuit.
We chose to power Big Bird’s lift fan system with a 7.2V 2-cell Team Orion Carbon Edition Lithium Polymer battery.
The choice of Lithium Polymer for the battery type allows considerably longer run-time and lighter weight than other options, such as NiMH (Nickel Metal Hydride). The power density of these batteries, as well as their availability are why we went with these batteries.
For more information on the Novak GTB Motor control system, check out this link.
The Team Orion battery specifications can be found here.
Propeller Electronics
To provide forward and reverse thrust to Big Bird, we chose to use 2 Electri-Fly Rimfire 22M-1000 brushless motor systems.
These motors offer variable pitch-control of the propeller blades, allowing us to quickly shift between forward, reverse, turning, and at-rest behaviors all at a constant motor speed. Variable pitch control avoids excessive wear and tear on the motor’s mechanical components and also prevents the propulsion battery and motor electronics from experiencing too much variability in voltage and current loads, which are clearly ideal for prolonged life.
The Rimfire motor specifications indicate that the device will operate between 7.2 and 12 V, though our experience showed that the effective range was more like 9-12 V.
The specifications for the Rimfire motor can be found here.
To power the Rimfire motor optimally (as close to 12 V as possible to achieve the greatest potential thrust), we chose to utilize a 11.1 V 3-cell Li-Po battery made by Hi-Model, shown below
More information on this battery can be found here.
Ultrasonic Input
To provide a proof of concept sensor for the Big Bird platform, we chose to add an ultrasonic distance sensor to the final prototype. Based on low cost, availability, and plug-and-play ease of use, we elected to use the Maxbotix EZ1 ultrasonic sensor, shown below
The EZ1 requires 2.5 – 5.5 V, and for our implementation was powered using the 3.3V power of the onboard circuit. This sensor’s specifications indicate that it offers ~6.4 mV/in analog output at this voltage, a factor which we found to agree well with observed values.
The pin diagram of this sensor is shown below
We connect Pin 1 to GND and Pin 2 to the +3.3V of the onboard circuit.
The sensor’s Pin 5 (AN) provides analog voltage output scaled to the distance reading. We connect this pin to AN0 on the onboard PIC, where it is converted into a digital reading and sent wirelessly to the host computer for display.
The datasheet for this ultrasonic sensor is found here.
While the sensor currently has no integral part in the performance of Big Bird, we believe it offers a nice proof of concept for Big Bird’s sensor potential. With 5 analog inputs (AN0 – AN4) available on the onboard PIC, plenty of future options for navigation control exist with the proper code modifications.
Project Big Bird required two circuits, each with specialized functions:
Onboard PIC circuit:
send/receive data from host PIC via wireless
controls the lift fan and propulsion fans via PWM output signals
reads sensors (convert analog to digital)
Host PIC circuit:
send/receive data from host computer via USB
send/receive data with host PIC via wireless
Photos of both are shown below.
Circuit Diagrams also appear below
Power
Onboard:
Takes in +6V from Novak Electronic Speed Control (ESC) Power Output
Runs entirely on +3.3V, produced by a voltage regulator
Host:
Runs on +5V from host computer
XBee module uses +3.3V, produced by a voltage regulator
Microcontrollers (PICs)
We choose to utilize microcontrollers from the Microchip Technology’s PIC18F family due to availability and our previous experience. The data sheet for this class of microcontrollers can be found here.
Electronically, these PICs require between 2.5-5.5 V, well within the range of both circuits.
Wireless Module
To achieve wireless data transfer between the host computer and the onboard lift and propulsion fans, we chose to use a XBee Pro OEM RF Module, as shown below
The XBee provides a low cost, low power solution to the wireless communication. It offers a 300 ft range over a standard 802.11 frequency. The device is ready to operate right out of the box with minimal support circuitry. A pin diagram is shown below
Pins 1 and 10 must be connected to +3.3V and GND, respectively. Pin 2, the XBee’s data output node, connects to pin 18 of each PIC. Similarly, pin 3, the XBee data input, hooks in to PIC pin 17. These four connections are all that is necessary to send and receive byte data wirelessly between PICs.
For more information on the XBee OED RF module, check out the manufacturer data sheet.
Lift Fan Electronics
Big Bird’s lift fan is a Novak GTB/SS 10.5 Pro Brushless System, which includes the motor, the speed control, and other necessary components.
This system requires 4.8-7.2 V to run, which motor performance increasing as the input voltage approaches 7.2 V.
The lift fan system’s electronic speed control (ESC) provides a +6V power output alongside the white signal cable which provides PWM control of the lift fan. This +6V was down-regulated to +3.3V and used to power the onboard circuit.
We chose to power Big Bird’s lift fan system with a 7.2V 2-cell Team Orion Carbon Edition Lithium Polymer battery.
The choice of Lithium Polymer for the battery type allows considerably longer run-time and lighter weight than other options, such as NiMH (Nickel Metal Hydride). The power density of these batteries, as well as their availability are why we went with these batteries.
For more information on the Novak GTB Motor control system, check out this link.
The Team Orion battery specifications can be found here.
Propeller Electronics
To provide forward and reverse thrust to Big Bird, we chose to use 2 Electri-Fly Rimfire 22M-1000 brushless motor systems.
These motors offer variable pitch-control of the propeller blades, allowing us to quickly shift between forward, reverse, turning, and at-rest behaviors all at a constant motor speed. Variable pitch control avoids excessive wear and tear on the motor’s mechanical components and also prevents the propulsion battery and motor electronics from experiencing too much variability in voltage and current loads, which are clearly ideal for prolonged life.
The Rimfire motor specifications indicate that the device will operate between 7.2 and 12 V, though our experience showed that the effective range was more like 9-12 V.
The specifications for the Rimfire motor can be found here.
To power the Rimfire motor optimally (as close to 12 V as possible to achieve the greatest potential thrust), we chose to utilize a 11.1 V 3-cell Li-Po battery made by Hi-Model, shown below
More information on this battery can be found here.
Ultrasonic Input
To provide a proof of concept sensor for the Big Bird platform, we chose to add an ultrasonic distance sensor to the final prototype. Based on low cost, availability, and plug-and-play ease of use, we elected to use the Maxbotix EZ1 ultrasonic sensor, shown below
The EZ1 requires 2.5 – 5.5 V, and for our implementation was powered using the 3.3V power of the onboard circuit. This sensor’s specifications indicate that it offers ~6.4 mV/in analog output at this voltage, a factor which we found to agree well with observed values.
The pin diagram of this sensor is shown below
We connect Pin 1 to GND and Pin 2 to the +3.3V of the onboard circuit.
The sensor’s Pin 5 (AN) provides analog voltage output scaled to the distance reading. We connect this pin to AN0 on the onboard PIC, where it is converted into a digital reading and sent wirelessly to the host computer for display.
The datasheet for this ultrasonic sensor is found here.
While the sensor currently has no integral part in the performance of Big Bird, we believe it offers a nice proof of concept for Big Bird’s sensor potential. With 5 analog inputs (AN0 – AN4) available on the onboard PIC, plenty of future options for navigation control exist with the proper code modifications.
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Is the speed controller(ESC) for this project similar to those available on RC sites or did you design it on your own? Also, could you please shed some more light on how the ESC was used for control without using the receiver or transmitter? It would be really helpful if you could tell me what happens when we press the throttle stick, as in is there a PWM wave created depending on the throttle position, if so then what is the PWM frequency??
Thanks