Wireless User Interface for Variable Frequency Drives

Team 168Alex Shuster (EE)Michael Kloter (EE)Christopher Perugini (EE)Kevin Wei (EngPhys - EE)

Sponsor: Lenze Advisor: Professor John Chandy

Outline• Lenze•Objectives and Deliverables•Research and Proposed Solution•Hardware•Network Topology•Programming•Timeline•Budget•Future Work

LenzeProvide Motor Control Solutions

• Automotive Construction• Robotics• Manufacturing and Packaging

Variable Frequency Drives• Speed and control system for AC motor

Objective - DeliverablesCurrent Problem

• Manually Set Parameters• Limited Accessibility• Long Individual VFD Programming and

Reprogramming

Objective • Develop a wireless interface on the VFDs• Maximize the transmission distance• Monitor and transmit to multiple VFDs at

once• Able to operate in an industrial environment

Researched and Proposed Solution

Researched various wireless communication options such as Wi-Fi, Bluetooth, and ZigBee

Wireless Communication Choice: ZigBee• 10-100m / node• Low complexity, cost, power consumption• Low to medium data rate• Operational in an industrial environment

Technical Solution

Physical Layer ProtocolRS-485 Modbus

Ethernet Phy 802.3

CAN CANOpen

HardwareDevelop test application to validate wireless

implementation

Firmware and

Debug ONLY

Current HardwareComponents•Sparkfun

ATMEGA128RFA1•Sparkfun RS-485

Breakout

Hardware Configuration

ZigBee Lightweight Mesh• Basic data services (send and

receive data)• Acknowledgements• Routing• Basic security• Power management of the radio

transceiver• Network management (discovery,

joining, commissioning, etc)• Advanced network operation

scenarios (sleeping routers, parent-child relationship, data delivery to the sleeping nodes, etc)

• Retries to send data in case of failures

• Defining message payload format• Advanced security• Power management of the MCU• Interfacing hardware peripherals

(ADC, PWM, EEPROM, etc)

Transceiver SchemesOption One: FIFO Byte by byte The USART will receive 8 bits, then pass that to a buffer. This buffer vector will be inserted

into the ZigBee frame payload and the entire frame will be passed to the ZigBee radio frame buffer to await transmission

Option Two: FIFO MessageThe USART will receive 8 bits, then pass that to a buffer. The MCU will wait for a full modbus message to be received 8 bits at a time and save in a message buffer This message buffer will be inserted into the ZigBee frame payload and the entire frame will be passed to the ZigBee radio frame buffer to await transmission

Programming OptionsPredefined Buffer Size•Transmits when buffer filled

Variable Buffer Size•Transmits when timer triggered

Real Time Transmission•Transmit data as received

Predefined Buffer SizePrevious Method: 8 Byte Buffer Size•Would receive data bytes from the computer

and fill a buffer array of size 8, and then transmit all of the data.

Downside•The Techlink software sends varying message

sizes including up to 13 bytes.•The time required to transmit the full buffer can

conflict with new incoming data being stored.

Variable Buffer SizeMore Complicated Method•Makes use of the Modbus protocol•A timer is triggered if 3.5 characters go by

without data, this indicates that a complete message has been sent.

•Once the timer is triggered, the buffer will be sent to the VFD.

Downside•More complicated, and transmission times

can interfere with receiving new data.

Transmission as Data is Received

Easier method•As each data byte comes in from the

computer, it is transmitted to the VFD.

Downside•Greater overhead delays when the data is

transmitted over ZigBee due to packetization.

Programming ChoiceMethod Chosen:As Received•This allows for Lenze to adapt the code to

other applications .

•Will not restrict the use for future products.

BudgetLenze Grant: $1000

Product Quantity Unit Price PriceDesign EstimatesIn System Programmer 1 $35.36 $35.36Single Chip MCU and ZigBee

3 $9.75 $29.25

RS-485 to UART Transceiver

3 $2.70 $8.10

ZigBee Development Kit

1 $119.00 $119.00

Misc. Supplies $100.00Total: $290.71

Timeline

Future WorkZigBee PCB Antenna

• Researched PCB Antenna Designs• Easy to tune• Reduces Costs

MCU Integration• Via VFD’s RS-485 Option Module• Eliminate External Hardware• Wireless Upgrade Package

Questions