Nail Coil Gun

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
Gun Coil
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
Oscillating Circuit

• Overall Circuit
• Oscillating Circuit
• Boost Circuit
• Discharge Circuit

Discharge Circuit
Boost 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
• 500kO 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 isnt in
  use
• Voltage divider using 500kO 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 guns
  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 guns 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!