Designing An Electronic Trigger Mechanism For A Paintball Marker To Allow User Selectable Firing Rates ECE 4884/4007 Fall 2007 Nathan Densmore Matthew Roese Andrew Adams Chris Britton (Team Leader)

Georgia Institute of Technology ECE 4007 Fall 2007 Overview Design and implement an electronic trigger Upgrading is more practical compared to other high end electronic markers Target customers will be scenario paintball enthusiasts Principal expense is development cost

Georgia Institute of Technology ECE 4007 Fall 2007 Design Objectives Electronic trigger upgrade for the 98 Custom paintball marker Two firing modes: semi-automatic and fully automatic LCD screen will display the mode and selected rate of fire LED indicator for low ammunition and selected firing mode User friendly up/down buttons to select the rate of fire

Georgia Institute of Technology ECE 4007 Fall 2007 Design Approach Key component is PIC Microcontroller (16F690) Powered by 9V battery Trigger pressed will activate the micro switch allowing 9V signal to energize the solenoid PIC will output to an LED indicating firing mode PIC will output to LCD module indicating firing mode and rate

Georgia Institute of Technology ECE 4007 Fall 2007 Top Level Design of Circuit Components

Georgia Institute of Technology ECE 4007 Fall 2007 PIC Controller 20 pins – 1 VDD, 1 VSS, up to 18 I/O pins Operates on V Up to 20MHz oscillator/clock Up to 200ns instruction cycle 8-bit and 16-bit timer/counters FLASH/EEPROM – up to 100,000 writes

Georgia Institute of Technology ECE 4007 Fall 2007

PIC Programming Environment MPLAB Integrated Development Environment (IDE) included as tool to program PIC MPLAB is programmed in assembly language PIC Kit 2 software responsible for debugging code and loading chip

Georgia Institute of Technology ECE 4007 Fall 2007 Pseudo-code Example Set BPS default; Set Ball Count; When ROF switch  Semi or Full LED if Semi ROF  GREEN Solid if Semi ROF  RED Solid LCD if Semi ROF  Display “Semi” if Full ROF  Diplay “Full” and BPS PUSHBTN if Full ROF  when UP PUSHBTN  BPS + = 1 when DOWN PUSHBTN  BPS - = 1 when UP & DOWN  BPS = 0, Go to LED, LCD

Georgia Institute of Technology ECE 4007 Fall 2007 Power Supply Schematic

Georgia Institute of Technology ECE 4007 Fall 2007 Debounced Trigger Circuit “Beginning” of circuit, and activated when trigger is pulled Switch will send a high input to the PIC controller

Georgia Institute of Technology ECE 4007 Fall 2007 Push Buttons (Up/Down) UP and DOWN pushbuttons are inputs to the PIC; used only when in Full Auto Mode UP pushbutton will increase firing rate; DOWN will decrease firing rate Both UP and DOWN selected simultaneously will RESET ball count

Georgia Institute of Technology ECE 4007 Fall 2007 LED Mode Indicator Semi Mode: Green LED Full Mode: Red LED Low Ammo Status: LED alternates red and green

Georgia Institute of Technology ECE 4007 Fall 2007 LCD Module Display numbers and words More versatile than 7- segment LED Line length 8 characters 14 pins in order to interface PIC controller 8 data lines, 3 control lines, & 2 power lines Time delay between LCD and PIC interface

Georgia Institute of Technology ECE 4007 Fall 2007 Solenoid Powered by +9V PIC outputs +5V and closes transistor circuit Current freely flows and fires the solenoid PIC outputs 0V and opens transistor circuit Current stops flowing and solenoid returns to initial state Diode prevents residual current from damaging transistor

Georgia Institute of Technology ECE 4007 Fall 2007 Mechanical Operation Operator pulls trigger Trigger throws trigger switch Solenoid fires and forces rod upward Rod rotates sear rocker pin and releases bolt Bolt spring sends bolt forward inducing firing operation Blowback resets bolt, locking sear into initial position Solenoid magnet resets solenoid to initial position

Georgia Institute of Technology ECE 4007 Fall 2007 Component Enclosure Plastic enclosure will mount on marker’s magazine Enclosure will house all of the electronic trigger assembly

Georgia Institute of Technology ECE 4007 Fall 2007 Technical Advantages and Disadvantages LCD module is more flexible than 7-segment LED display Relatively inexpensive production cost Circuit components are easily replaceable98 Circuit design larger than existing products LCD module is bulky

Georgia Institute of Technology ECE 4007 Fall 2007 Marketing Advantages Ability to change firing modes quickly Able to change rate of fire efficiently Easy operator interface allows for quick selection of system configurations LCD data display No special tool or manual to switch modes or firing rates

Georgia Institute of Technology ECE 4007 Fall 2007 Cost Analysis Design Cost PurchasedItem DescriptionQuanityUnit PriceAmount Digi-Key CorporationResistor 4.7K Ω Digi-Key CorporationResistor 1K Ω10.15 Digi-Key CorporationResistor 150 Ω Digi-Key CorporationNPN Transistor10.11 Digi-Key Corporation2-In Nand Gate Digi-Key CorporationRectifier GPP 50V10.26 Digi-Key CorporationLever Switch11.10 Digi-Key CorporationPushbutton Switch Digi-Key CorporationRocker Switch11.80 Digi-Key CorporationRegulator10.72 Digi-Key CorporationCapacitor.1µF10.11 Digi-Key CorporationCapacitor.33µF10.15 Digi-Key Corporation9V Battery Lead10.33 Digi-Key CorporationLED Light10.75 Digi-Key Corporation8x1 LCD Module Digi-Key CorporationPIC16F57 28-DIP11.55 Digi-Key CorporationPIC16F628A 18-DIP13.35 Digi-Key CorporationPICKIT 2 Starter Kit Adv. Paintball ElectronicsSolenoid Tippmann PartsBag of Parts for Trigger Shipping Cost Total Design Cost

Georgia Institute of Technology ECE 4007 Fall 2007 Future Work Program the PIC microcontroller to fire paintball marker (2 weeks) Design an etched circuit board for more efficient production (1 week) Program PIC microcontroller to work with LCD module (4 days) Assemble product and test on marker (3 days)