Testing Power Board

From HotDec

Jump to: navigation, search

Contents

[edit]

BATMAN 4 Testing Procedures

  1. Once you have assembled the entire batman board, check the change markings on the master layout and verify that the components you used for the board, match what is specified on the master layout. The master layout is specifically for changes to component values that were made after the boards were produced. Thus any conflicts between the master layout and with the silk screening should be resolved by using the values specified on the master layout.
  2. Using the precision power supply, set the voltage limit on the +25 volt output to 12volts and the current limit to 0.100 A. Connect the output of the 12v supply to the Thruster Battery input (yellow). Turn the power supply output on. If the board is completely working no current should be used by the power board (because the power board should start out in the OFF state)
  3. Turn the output of the power supply off, and move the connector from the Thruster Battery input to the SBC Battery input (blue). Turn the power supply output back on. As with the thruster batteries the power board should not use any current.
  4. Change the precision power supply current limit to 400mA. Short the START pins together to turn the board on. The “SBC On” LED should light up. Verify that the DC/DC converter is producing 5v.
  5. Turn the power board “OFF” by shorting the STOP pins together. The “SBC On” led should turn off. Make sure the DC/DC converter is no longer producing 5v.
  6. Turn the output off on the precision supply and disconnect it from SBC battery input. Change the supply voltage to 13.8v and current limit to 400mA. Then connect the supply to the AC power input (green).
  7. Turn the supplies output power on. The yellow and green LEDs on the edge of the board should all turn on. Also the two red LEDs near the back of the board (D40 – Thruster Connected & D32 SBC Connected) should also turn on. The board should use about 100mA of current.
  8. If the LEDS are very dim or seem to flash, there is most likely a problem with the board. Take a look at Zero Volt Mode Error.
  9. Check the output voltages for the thruster and SBC they should be between 12.56 and 12.6 volts.
  10. Once again turn the power board on by shorting the START pins together. Check that the DC/DC converter still produces 5v. The center debugging LEDs may or may not turn on (because the LEDs driver starts out in a random state). The power board should use between 100-230mA depending on how many LEDs turn on.
  11. Once again turn the power board off by shorting the STOP pin together. The “SBC On” led should turn off and the DC/DC converter should stop producing 5v.
  12. Put a jumper connecting the “T_DIS” pins this will disable thruster battery charging. The “Thruster Connected” and the “T_ENABLE” LEDs should turn off. Make sure the voltage on the thruster battery connector drops to 0 volts (the voltage on the pins will likely drop off slowly after charging is disabled).
  13. Put a jumper connecting the “S_DIS” pins, this will disable SBC battery charging. The “SBC Connected” and “S_ENABLE” LEDs should shut off. Make sure the voltage on the thruster battery connector drops to 0 volts (the voltage on the pins will likely drop off slowly after charging is disabled).
[edit]

Low Voltage Kill

The power board has the ability to turn off if for any reason either the thruster battery or the SBC battery voltage drops below 10v. This protects the batteries from being over-discharged accidentally.

  1. For this step the SBC and thruster charging disable must work correctly. If it doesn’t the power board will attempt to “charge” the precision power supply (which isn’t a good thing).
  2. For this step you will also need the precision power supply and another power supply capable of producing 13.8 volts (I used the 20amp black power supply). Adjust the 20amp power supply’s output to be approximately 13.8 volts and connect the output of the power supply to the AC power (green) input of the power board.
  3. Make sure the neither the SBC nor thruster charging is disabled, and that there is 12.6 volts on the thruster and SBC battery connectors. Turn the power board on by shorting the “START” pins. Put jumpers on both the “SBC LVK En” and “Thruster LVK En” pins. The power should not turn off when this is done.
  4. With the power board still on, add jumpers on the “SBC LVK En” and “Thruster LVK En” pins, put a jumper across the “T_DIS” pins. After a few moments the power board should turn off (because the thruster battery voltage will drop below 10v).
  5. Remove the T_DIS jumper and turn the board on once again. Repeat step 4 instead putting a jumper across the S_DIS pins. The power board should once again shut off.
  6. Now that the low voltage kill operation has been tested, the actually voltage cutoff points of about 10v should be verified. Remove both the “SBC LVK En” and “Thruster LVK En” jumpers”. Add jumpers across the “T_DIS” and “S_DIS” pins.
  7. Set the precision power supply’s current limit to 100mA and voltage limit to 12v.
  8. Turn the power board on. Connect the precision power supply to the thruster battery port. Put a jumper across the “Thruster LVK En” pins. Slowly reduce the precision power supply voltage from 12v until the power board shuts off. The power board should shut off at a voltage of about 10v.
  9. Repeat step 8 testing SBC low voltage kill instead.


[edit]

MCU/SBC Control

The MCU should be able to:

  • read the voltages of the batteries
  • turn on and off charging of the SBC batteries
  • select between using AC power and battery power for the SBC
  • turn off the power board
  • measure the current the batteries are charging at
  • control the leds of the power board

NOTE: these functions are availible to the MCU, but not all version of the MCU firmware will export this ability to the SBC.


[edit]

Charging Current Settings

The power board has the ability to measure the amount of AC input current it is using as well as the amount of current battery is being charged with. The AC input current is not equal to the charging current because some power is used for the components on the board itself as well as the DC/DC converter that powers the SBC. The power board has the ability to limit both AC input current and the battery charging current. The power board has 2 separate charging circuits, one for the SBC batteries and one for the thruster batteries. Each circuit is setup to measure exactly the same AC input current, but measures its own battery charging current. For each charging circuit the “ACSET” POT sets the limit of the current used by the power board, and the “SRSET” POT set the limit of the battery charging current. The lithium polymer batteries should be only charged with a 1C current (where C is the capacity of the battery pack in Amp-Hours). The thruster battery harness contains 4x 2100mAh batteries ( = 8.4 Amp-Hours) so its max charging rate current should be 8.4amps. The SBC battery pack is 1500mAH so its max charging current should be 1.5 amps. To give a margin of safety the power board its set to charge the thruster battery packs at 8 amps and the SBC battery pack at 1 amp. The amount of current that can be safely drawn from the power supply is ??. The fact that multiple hovercraft could be charging at the same time should be taken into account when the AC current charging limit is determined, though for the most part the AC current limit will higher than the current the power board will ever use for powering the SBC and charging the batteries. Testing the current settings is somewhat difficult to do but can be done in two steps. In the first step each circuit is tested to verify that the current limiting circuits actually do work (using a small current setting). In the second step the power board is tested charging at its full rate and the current limit pots can be tweaked to get the charging current to be correct.

[edit]

Step 1 – Testing current limiting.

For this step a mildly under voltage (less 12.6 volts) battery pack is needed. It doesn’t matter if the it is a SBC battery pack or thruster battery pack because we will keep the charging current to be less than 500mA.

  1. Connect the AC input (green) of the power board to a power supply that is producing 13.8 volts through a multi-meter so that the current being used by the power board can be measured. You can’t really use the precision power supply because its can’t produce enough current.
  2. Set both the SBC and thruster SRSET voltages to 0.1v and both the ACSET voltages to 1.0v. Setting the ACSET voltage much higher than the SRSET voltage effectively makes only the SRSET setting the limiting factor for the power board current usage.
  3. Connect the slightly discharged battery (10v to 11.6v) to a multi-meter then to the thruster battery output (yellow) of the power board so that the multi-meter can measure the current going to the battery. Check to make sure the current going into the batteries is low (about 400mA)
  4. Change the SRSET voltage, the battery charge current should also change. Below is a table of SRSET settings and the currents that corresponded to them. AFAIK these low settings and currents may very a lot from board to board.

Thruster SRSET voltage (volts) Battery Current (mA) for Board #4 Battery Current (mA) for Board #3 Battery Current (mA) for Board #5 0.10 390 330 340 0.13 490 410 430 0.16 620 500 530 0.20 820 630 660

  1. Unplug the battery, and change the ACSET setting to 0.1 volt and the SRSET setting to 1.0v. Move around the ACSET voltage and the watch the input current to the board. Below is a table of different ACSET settings and the input current that was measured with them.

Thruster ACSET voltage (volts) Input Current (mA) for board #4 Input Current (mA) for board #3 Input Current (mA) for board #5 0.10 300 270 345 0.13 570 480 557 0.16 840 670 756 0.20 1250 900 990

  1. Repeat step 2 to 5 Attaching the battery to SBC connector (blue) and changing the SBC SRSET and ACSET setting instead.

SBC SRSET voltage (volts) Battery Current (mA) for Board #4 Battery Current (mA) for Board #3 Battery Current (mA) for Board #5 0.10 250 180 360 0.13 350 290 480 0.16 470 400 590 0.20 640 550 740

SBC ACSET voltage (volts) Input Current (mA) for board #4 Input Current (mA) for board #3 Input Current (mA) for board #5 0.10 170 300 202 0.13 560 540 455 0.16 930 770 708 0.20 1440 1020 984


[edit]

Step 2 – Full on charging

The goal of this step is to do a final test of the power board on a complete hovercraft to make sure it handles the required charging current correctly. 1. Hook-up power board to


[edit]

Common Problems

[edit]

Zero Volt Mode Problems

When the power board first gets AC power and there is no SBC battery (or no Thruster battery plugged in). The power board with initially sense there zero battery voltage and go into Zero Volt Mode and it will disable charging (which in theory would be perfectly reasonable since there is no battery connected anyway). What the battery charging board does do is provide a small amount of current to the battery. With no battery present this small amount of current should be enough to bring the battery voltage high enough so that the battery comes out of zero charging mode and starts charging the battery normally (using the Buck Filter). But, problems could exist that prevent the small amount of zero-voltage-mode current from reaching a high enough voltage to leave zero-volt-mode.

[edit]

Normal charging is broken

When the battery charging voltage reaches a high enough level (80% alarm voltage) the charging chip will switch out of zero-vole-mode and start normal charging. When this happens the small zero-volt charging current (through resister ??) is disabled. If normal charging does no kick in then the charging voltage will slowly drop back to the level where zero voltage charging is once again enabled. This will make the “SBC Connected” LED to repeatedly grow dimmer and then brighter. If you use an oscilloscope and look at the battery charging voltage you will see it creates a quasi-triangular. See broken charging for reasons why normal charging would not work correctly

[edit]

IC that uses too much power

On the power board, the battery charging output is used by more than just the batteries (this is especially true of the SBC side). The battery charging output is used by some IC and LEDS on the power board itself. If (for some odd reason) these components happen to use more current than is provided by zero-voltage-mode the battery output voltage will never reach the needed level to enable normal charging. But this will not be a problem once normal charging is enabled, so if the power board is brought out of zero charging mode momentarily (for instance, by connecting the board to a battery for a split second) it should stay that way.

[edit]

Broken ACDRV (only applies to SBC charging)

The DC/DC converter that powers the SBC can get power from one of two sources: (1) the SBC battery; (2) the AC power input. There are two mosfets that act as a switch that selects which source power to SBC comes from. The two mosfets are controlled by the BATDRV and ACDRV pins on the bq24702. The bq24702 has internal circuitry that will select the source that is available, or if both AC power and the SBC Battery are present the bq24702 will use the ACSEL input to determine what source to use. For the SBC battery to charge the AC input must power the DC/DC converter. If the SBC was using power to the battery while it was charging there would be a problem because the SBC could be using more current from the battery than it would be charging with. The bq24702 will not enable battery charging if its ACSEL input is used to select battery power. But, if for some reason the ACDRV mosfet or the ACDRV pin doesn't work the SBC cannot get its power from the AC input. The SBC can still get power from the SBC battery through the body diode of the BATDRV mosfet. This will cause the following problems:

  • When the SBC is plugged in the SBC Battery charging current setting (SRSET) will be need to be much high that normal (since the SBC is using the current that is being used to charge the SBC).
  • The SBC battery charging current will jump around (even through it should be constant). This is because the SBC will use a varying amount of current
Retrieved from "http://elegy.mie.uiuc.edu/mediawiki/index.php/Testing_Power_Board"
Personal tools