APA-I DESIGN

OVERVIEW / DESIGN / CONSTRUCTION / PERFORMANCE

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PRIMARY DISPLAY

The primary display PCB is a voltmeter utilizing the ICL7107 3 1/2 Digit, LCD/LED Display, A/D Converter. This circuit reads the voltage from the capacitor bank and displays it using 3 7-segment blue LED displays. A max16054 is used to toggle the display brightness with a small push-button on the bottom of the board. In addition a series of 4 separately driven dual LEDs show the following circuit states: Power, CPU (Microcontroller) Status, Charge Status, Fire (Ready) Status, and Error Status.

 

SECONDARY DISPLAY / LED AND LASER CONTROLLER

The secondary display PCB is a bar graph voltmeter utilizing LM3914 bar graph display driver as well as two push-button controllers for easy LED/LASER switching. The LED and LASER are controlled via a single push-button close to the handle.

INFRARED OPTICAL INTERRUPT SENSOR

The sensor PCB senses the presence of the projectile by reflecting infrared light. Once the sensor is triggered a signal is sent to the micro-controller and the micro-controller activates the accelerator after a small time delay.

LOW VOLTAGE POWER MANAGEMENT AND MICRO-CONTROLLER

The low voltage power management board provides the entire system with regulated 16V and 5V rails. These are regulated by means of SEPIC and buck converter circuits respectively. The micro-controller will also be placed on this board with an in-circuit programming connector. The majority of the wiring will be directly soldered to this board and be connected to other PCBs via board level connectors.

CAPACITOR DISCHARGE

The capacitor discharge board will be the most stressed part of the system. Currently only one passive test board exists although a total of two boards will be mounted on each side of the accelerators when testing is complete.  Each board will have 4 primary switching IGBTs along with 1 passive snubber. The circuit diagram shown below shows the injector and stage one capacitor discharger. This setup is subject to change as required and as performance is tested.

Capacitor Discharge PCB

BATTERY MANAGEMENT  (CANCELLED)

The original battery management board provided the lipoly batteries with over-voltage, under-voltage, reverse-voltage, over-current, and cell-balancing. However when testing the board with the ultra-high initial current draw of the LT3751 test PCB the protection IC would isolate the battery. After a very large number of fixes and troubleshooting the problem could not be resolved. Therefore the original battery management board was scraped and the protection circuitry was integrated into the high voltage power management board. The cell balancing will be completed by a commercial lipoly battery charger. The original circuit and PCB are shown below for reference.

HIGH VOLTAGE POWER MANAGEMENT AND BATTERY PROTECTION

The high voltage power management board acts as a regulated capacitor charger, a battery management board, and a circuit/battery protection board. The LT3751 limits the voltage range the circuit will use and additional protection circuits provide re-settable over current and emergency shut-down functions. The circuit diagram shown below shows both the high and low voltage components and does not include the new battery protection components. When the PCB is validated I plan to update the circuit diagram. The PCB on the right will be the final high voltage power management board (includes the protection features) included in the system however. So far initial tests show it works as expected, however power output and fault testing still need to be conducted.

 

OVERVIEW / DESIGN / CONSTRUCTION / PERFORMANCE

 

© 2007-2015 Robert Wilsford.

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