1. Cordless Electric Nailer
Team 27: Nithin Reddy and Mohammad Farooq Shaik
Ece 445 Senior Design Project
Team 27

2. Introduction
A battery powered nailer will provide the user with a sense of portability that current models do not.
Our goal is to develop an efficient DC motor controller for the mechanical component of the nailer.

3. Objectives Design a low powered DC motor Controller. Inexpensive.
Develop enough energy to drive a nail.
Create a battery monitoring system.

4. System Specifications
Input:
10-18 Vdc
Output:
15 Vdc ±2%
Power Ratings:
250W Continuous
500W Peak for 1 minute

5. System Outline Power Supply Battery Charge Display PWM UC 3825
Buck Converter
Mechanical Component
H-Bridge Driver
LS 7260
H-Bridge
DC Motor
Control Module
Voltage Regulator Module

6. Battery Charge Display
Consists of 3 LEDs
Green – Battery is full.
Yellow – Battery is 60-70% full.
Red – Battery is getting low
Variable resistors can adjust the thresholds of the 3 LEDs

7. Battery Charge Display Testing
Circuit was tested by applying a variety of voltages.
The respective LED lights up for the voltage applied.
If the LED did not light up, it was tested to see if the LED was faulty.

8. Battery Charge Display
Vo >14.5 volts
14.5 V> Vo > 12.5 V
12.5 V> Vo
Vo = Battery voltage

9. Control Module Pulse Width Modulation (UC3825)
Compares the output voltage from the voltage divider circuit to the internal reference and adjusts the duty cycle accordingly.
H bridge driver (LS7260)
Direct drive control of MOSFETs.
Controls direction of DC motor.
Ability to stop the motor at any instant.

10. Buck Converter Step down DC-DC converter.
Maintains constant output of 15 volts.
Simulated Boost Converter Output

11. Buck Converter Testing
Tested the buck converter circuit with varying voltages.
Ensured that the output voltage was 15 volts regardless.

12. H Bridge 4 MOSFETS( 2 P type and 2 N type).
2 MOSFETS are on at one time.
Controls the direction of the motor.

13. H Bridge
When S1 and S4 are on, the motor moves in an anticlockwise direction
When S2 and S3 are on, the motor moves in a clockwise direction

14. Mechanical Component
Currently being created by mechanical engineering senior design team
Motor will rotate and will cause spring to compress and expand.
Expanded Spring
Collapsed Spring

15. Successes Battery powered. Low Power Requirement. Inexpensive.
Ability to control motor direction.

16. Difficulties Speed control of the DC motor with the PWM chip.
Winding of the Inductor.
Searching for high current resistant MOSFETS.
Understanding Chip Functionality.

17. Recommendations
Finalize circuit design before submitting a PCB request.
Obtain compatible high power motors to test at desired power levels.
Use Power Lab: Less crowded, Familiar Equipment and access to motors.
PCB layout to improve efficiency and avoid parasitics (stray capacitance and inductance).

18. Questions?