ECE 477 Digital Systems Senior Design Project Fall 2005
Homework 13: User Manual
Due: Monday, May 1, at 5:00 PM
Team Code Name: ______H.E.A.D. Gear______Group No. ___12___
User Manual Outline:
§ Brief (marketing-style) product description
§ Product illustration annotated with callouts for each control/display
§ Product setup instructions
§ Product use instructions
§ Product troubleshooting instructions
Evaluation:
Component/Criterion / Score / Multiplier / PointsProduct description
/ 0 1 2 3 4 5 6 7 8 9 10 / X 2Product illustration with callouts / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Product setup instructions / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Product use instructions / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Product troubleshooting instructions / 0 1 2 3 4 5 6 7 8 9 10 / X 2
TOTAL
Product Description
The H.E.A.D. Gear MPPT (Maximum Power Point Tracker) is designed with ease of use, versatility, and robustness in mind and is targeted towards solar cars. The MPPT is a heavy-duty electronic product. It is manufactured with state-of-the-art PCB processes and features vibration resistant connectors and components. To ensure ease of use, all that is needed for operation is a solar array, a load battery and a 12V power supply. Once these three things are present, the MPPT will start on its own, measure the parameters of the solar array to which it is connected, find the operating point that yields the maximum possible power output of the solar array, and begin operating at that point. Without user intervention, the MPPT will continue to track this “Maximum Power Point” (MPP) and will dynamically adapt to changing solar conditions such as clouds, solar irradiance angle (angle at which the sun’s light strikes the solar array) and temperature change to maintain the MPP of the solar array.
With the ability to be connected to an advanced, high-speed CAN network, the MPPT can provide high-criticality operating information and parameters in a near real-time manner. The MPPT implements a CAN protocol designed for Purdue Solar Racing which allows up to 16 MPPTs to be used simultaneously. All major operating parameters of the MPPT including input and output voltage and current as well as temperature and operating status can be obtained through the CAN network. In addition, the operating state of the MPPT can be changed through the CAN network, allowing complete remote control and monitoring of the MPPT.
With its versatile debug mode, the MPPT can act not only as a power converter for a solar array, but as a solar array measurement, analysis, and diagnostic platform. The debug mode allows for operating parameters to be monitored without the use of the CAN network by communicating through a standard serial port. In addition to this, the current vs. voltage curve of the solar array connected to the MPPT’s input can be continually mapped in the debug mode, which is a powerful diagnostic and characterization tool for solar arrays. All that is needed for debug mode operation is an RS-232 level translator board and a standard PC with a serial port capable of 57.6kbps operation (not included).
Product Illustration
Figure 1: MPPT Illustration
Figure 2: Fan Connector Detail Figure 3: Temperature Sensor Detail
Figure 4: Programming and Debug Connector Detail
Figure 5: Main Power Connector Detail
Figure 6: CAN Connector Detail
Figure 7: RS-232 Level Translator Board Detail (not included)
Product Setup
The MPPT can be operated without utilizing any of the higher-level data reporting functions, temperature sensing functions, or fan control functions. The MPPT will find the maximum power point of the solar array and continually convert power into the load batteries, however, the Error LED (see Figure 1) will be illuminated at all times. To utilize only the power conversion functionality of the MPPT, follow the steps outlined in the “Main connections necessary for operation,” to utilize the additional functionality present in the MPPT, follow the subsequent sections pertaining to the specific features.
Main connections necessary for operation:
1. Connect the negative terminal of the main car battery to the negative terminal of the MPPT (Figure 5), then connect the positive terminal of the main car battery to the positive terminal of the MPPT.
2. Connect the negative terminal of the solar array to the negative terminal of the MPPT (Figure 5), then connect the positive terminal of the solar array to the positive terminal of the MPPT.
3. Connect a 6-pin MTE cable (Figure 6) with at least +12V and GND present to one of the two CAN connector receptacles of the MPPT. The MPPT will then measure the solar array and will then enter normal operation, as indicated by the Heartbeat LED (Figure 1) blinking.
Utilizing CAN:
Note: At least one other CAN capable device that implements the Purdue Solar Racing CAN Protocol (at 125kbps bus speed) must be available for utilization of the CAN functionality. In addition, the CAN network must be terminated at both ends with 120Ω resistors for the network to function properly. It is assumed that the steps outlined above have already been completed.
1. Set the CAN ID Dipswitch (Figure 1) to the CAN ID required (in binary). For example, if a CAN ID of 7 were required, the switch positions, from left to right, would be: DOWN-UP-UP-UP (or OFF-ON-ON-ON or 0111).
2. Connect a 6-pin MTE cable (Figure 6) with at least the CAN_H, CAN_L, and loopback wires present to one of the available CAN connector receptacles of the MPPT.
3. Connect the other end of this cable to the existing CAN network.
4. Power-cycle the MPPT to re-start it by removing the 6-Pin MTE connector with +12V and GND present and re-inserting it again.
5. The MPPT will now measure the solar array and then enter normal operation, as indicated by the Heartbeat LED (Figure 1) blinking.
Entering Debug Mode:
Note: It is assumed that the MPPT already has power present on one of the CAN connector receptacles and that normal operating mode has already been entered.
1. Connect the RS-232 level translator board (Figure 7) to the Debug Connector (Figure 1).
2. Connect the output of the RS-232 level translator board to the serial port of a PC.
3. Open HyperTerminal and connect to the appropriate serial port with communications settings of 57600bps, 8 data bits, no parity bit, and 1 stop bit.
4. Press any key and the debug mode will be entered. Note: If the MPPT is measuring the solar array, it may take a couple of seconds to enter debug mode.
Utilizing Temperature Control:
1. Connect the TC1047A sensor board (Figure 3) to the temperature connector receptacle (Figure 1).
2. Connect any 12V DC fan utilizing the pin-out shown in Figure 2 to the fan connector receptacle (Figure 1).
3. If the MPPT is powered, power-cycle the MPPT to ensure proper operation.
Product Operation
To operate the MPPT in normal mode, only the connections specified in “Main connections necessary for operation” need to be made and the product will enter normal operations mode on its own.
CAN Protocol
The MPPT utilizes a CAN protocol developed for the Purdue Solar Racing Team. This protocol defines how data is accessed from the MPPT and how the MPPT is controlled via the CAN network. A data request for the MPPT consists of a CAN message using the CAN ID of the required MPPT as the CAN identifier, sending 0xFF as the first byte of message data to indicate that a value is being requested and then using the second byte of message data to indicate what particular piece of data is being requested from the MPPT (see Appendix A for a listing of possible values). The MPPT, upon recognizing a valid request, responds by sending a CAN message with an identifier of 0x011, the first byte of message data indicating the particular piece of data that is being sent back and the subsequent bytes of message data containing the actual value requested, in Little Endian byte order. Table 1 shows a sample message transaction.
To disconnect the solar array from the MPPT using its on-board relay, a CAN message can be sent to the MPPT of interest using its CAN ID as the CAN identifier, sending 0xFE as the first byte of message data, which indicates to the MPPT that a change of state is requested, and finally sending either 0x01 or 0x00 as the second byte of message data to either connect or disconnect the solar array, respectively. The MPPT does not respond to these messages, but does set a flag in the FLAGS register (which can be read via CAN) indicating the array connection status.
CAN Message ExamplesCAN Message ID (11-bit) / 1st Data Byte / 2nd Data Byte / 3rd Data Byte / Description
0x005 / 0xFF / 0x2A / N/A / Requests input current
from MPPT5
0x011 / 0x2A / 0xAC / 0x01 / MPPT 5 responds back with an input current of 4.28A
0x003 / 0xFE / 0x01 / N/A / Requests that MPPT3 connects its solar array
Table 1: Sample CAN Messages
Debug Mode
To enter the debug mode, make the connections specified in “Entering Debug Mode” and the product will enter debug mode. This mode is detailed below. An example of the HyperTerminal setup for debug mode is shown in Figure 8.
Figure 8: HyperTerminal Setup
Once the debug mode is entered, the menu in Figure 9 is displayed. The options “Send CAN Message” and “Monitor CAN Network” are will be implemented in the next release of this product and as such, do not do anything.
Figure 9: Main Debug Menu
From this menu, various parameters of the MPPT can be monitored and changed. If it is required to continuously sweep the I-V (current-voltage) curve of the solar array that is connected to the MPPT, choose Option 3. The output is TAB-delimited and the new line is output with a Carriage Return and Line Feed to make it easy to display in the terminal window as well as allow programs like Microsoft Excel and Lab View to parse the data easily. The order of the data is: Duty (divide by 500 to get %Duty), Input Voltage, Input Current, Output Voltage, and Output Current. All values except for Duty are multiplied by 100 to give two-decimal-point resolution to the printed integer. An example of the output is shown in Figure 10. To exit the IV Curve Trace mode, press the ESC key.
Figure 10: IV Curve Trace Output
If it is necessary to set the duty cycle of the MPPT to a permanent value or disable the PWM output (only while in debug mode), choose option 4. Once that option is chosen, the menu of Figure 11 will be displayed. To set the duty cycle, choose option 1 and enter an integer value between 0 and 500 (or enter the %Duty cycle by multiplying the required % Duty by 5 and rounding) and then press the ENTER key. To disable the PWM output, choose option 2. To go back to the main debug menu, press the ESC key.
Figure 11: Set Duty Menu
If it is wished to read the values of the various voltages, currents and the temperature of the MPPT, choose option 5 in the main menu. The MPPT will then begin outputting all of the values being measured onto the terminal as shown in Figure 12. The output is not meant to be used for data logging as there is text present in addition to the integer values, however spaces are used to separate the values from each other and from their descriptors and a Carriage Return and Line Feed end each line if parsing of the data by a program is required. Press the ESC key to return to the main menu from this mode.
Figure 12: Read A/D Values Output
To change the state of the ports on the microcontroller present in the MPPT, select option 6 in the main menu. Once this option is selected, the menu shown in Figure 13 will be displayed. Once an option from this menu is selected, the last line shown in Figure 13 will be displayed and the device that corresponds to the option selected will be turned on or off with a “1” or “0” key pressed, respectively. To return to the main menu from changing a port press the ESC key twice, otherwise, press the ESC key once to return to the main menu from the “Change a port” menu.
Figure 13: Change a port Menu
Product Troubleshooting
As the MPPT performs power conversion, there are components that, if damaged or used improperly, can cause a fire or explosion, so the warnings listed in the red boxes in previous sections and common sense must be exercised when using this product. The list of troubleshooting tips below is not meant to be exhaustive or a step-by-step guide to fixing the MPPT in the case of failure, but is meant to help point the user in the direction of the possible causes of the problem and some potential avenues for the repair of the product. It is assumed that the user is familiar with common electronic diagnostic tools such as DMMs.
Heartbeat LED Not Blinking
Possible Causes: Damaged LED, MPPT code failure, +12V not present on one of the CAN connectors.
Things to check: Ensure that +12V is present to the MPPT, this can be accomplished by measuring pin 4 on either of the CAN connectors (J1 and J2 on the board). If +12V is present, try power cycling the MPPT and seeing if the LED starts blinking after a few seconds.
Error LED Illuminated
Possible Causes: Input over-voltage condition, output over-voltage condition, input over-current condition, or MPPT over-temperature condition.
Things to check: Check the Flags register via the CAN bus. When this register is checked, all error flags are cleared and the Error LED will turn off if no error conditions still exist, otherwise the LED will remain illuminated and the Flags register will be set to reflect the error condition that still exists.