1. Nail Coil Gun ECE 445 Project: 20 Group: Andria Young, Seth Hartman TA: Ryan May

2. Introduction Purpose –To improve existing nail guns Features and Benefits –Light weight –Portable –No cords, cables, hoses

3. System Overview

4. Power 12V overall input for boost 5V for LM555, MOSFET driver, and op amp –Provided by 5V regulator 2V for reference voltage in op amp –Used variable voltage regulator tuned for 2V

5. Gun Coils Critically damped at 20uH Diameter as close to nail as possible Glue coil to prevent unraveling Length of coil to match nail length

6. Circuit Overview Overall Circuit –Oscillating Circuit –Boost Circuit –Discharge Circuit Oscillating Circuit Boost Circuit Discharge Circuit

7. The Oscillating Circuit Design LM555 astable timer Outputs 5V, 2kHz square wave as input to MOSFET DRIVER 95% Duty Cycle MIC4424 MOSFET driver to drive MOSFET in the Boost Circuit

8. The Oscillating Circuit LM555 square wave MOSFET driver signal

9. Boost Circuit Design Boost converter using 12V input to achieve ±10% 350V output Large inductance to increase charging speed 400V, 680uF capacitor to produce approx. 40J of energy during discharge 500kΩ bleed resistor Comparator to prevent capacitor from charging above 350V

10. Boost Circuit The inductor –Initial design called for.02mH inductor –Charge was too slow –Tried inductors from.02mH – 50mH –Charged fastest at 35mH

11. Boost Circuit The capacitor – 400V, 680uF – Discharge of ~15 minutes if capacitor isn’t in use – Voltage divider using 500kΩ bleed resistor as input to op amp – Used variable resistor to tune exactly when charging should stop

12. Discharge Circuit Design Sensor sees nail op amp output goes to 3.6V Output of op amp triggers the gate of the SCR Energy from capacitor discharges into the gun’s coil Sensor

13. Discharge Circuit Sensor –Signal from the sensor goes from hi to lo –Use LM2904 op amp to invert signal SCR –Output of the op amp triggers the SCR gate –SCR allows energy to be transferred –About 310A should pass through SCR to gun’s coil in less than 4ms

14. Discharge Curve

15. Discharge Circuit Solder small resistance where gun coil would go Charge the capacitor to ~50V Block the sensor Capacitor immediately discharged

16. Discharge Circuit What went wrong

17. Cost MOSFET - $2.33 x 5 Capacitor - $6.54 x 3 SCR - $1.54 x 5 Diode - $0.17 x 5 Voltage Meter - $5.00 x 2 Total - $49.82

18. Improvements Ring of capacitors for multiple fires Lithium Ion Batteries -Lightweight, high energy density

19. Questions? Thank you!