Engineering 44 Combot Peach Project

Combot: Peach JAR

Goal:
The objective of the project was to build a combat robot for an Ant Weight Combot Competition.

Criteria of Success:
1. The combot is able to navigate wirelessly.
2. A transistor-microcontroller circuit controls the flamethrower.
3. It is able to function after the deadly combot competition.

Main Materials:
-LaunchPad MSP430
-Toy Chassis
-Bluetooth Module
-2xVex Motorcontrollers 29
-2xMotors
-2xWheels
-Batteries

Weapon Materials:
-Fly swatter circuit
-Transistor
-Servo
-Gas Tank

Armor Materials:
-Polycarbonate
-Carbon Fiber Sheets
-Piano Wires

How it Works:
A bluetooth module is used to control the launchpad.
The Launchpad sends out different PWM signals to control the speed controller and servo.
The servo releases butane from a container while a transistor would turn on the sparker.

Conceptual prototype designs

First build for competition

The Mechanics:
-Sloped Front at 40°
-Wheel Protection
-Flamethrower weapon
-Center of Mass shifted towards the back to prevent flips

Schematics:
One Problem encountered was that the launchpad only worked at 3-5V while the other devices operated at 6-8V. A voltage divider was used for our initial circuit, but AA batteries were used in the second design.

Every ground is connected to a common ground else it will not work

Bluetooth Module Connected to Launchpad running on Batteries

Fly Swatter circuit connected to transistor and Launchpad

Peach moving via putty

Peach shooting fire via putty

Code to control the launchpad
The code is fairly simple as it replaces the Serial Monitor with a Bluetooth Monitor.
The Servo class controls both the servo and Vex Motor Controllers.
Motors run a range servo write values from 65 - 130.
- Going Backwards = 65 - 87 (fast to slow)
- Neutral = 88-100
- Going Forward = 101 - 130 (slow to fast)

Bill of Materials without Flamethrower:
- Launchpad MSP430 = Free
- Polycarbonate = $10
- Carbon Fiber Sheets = $27
- Bluetooth Module = $20
- Servo = Free
- Toy Body Chassis = Free
Total Cost : $57

Conclusion:
Without a weight limit, it is better to use AA batteries than to voltage divide one LiPo battery to 7 different components while watching for current, and the transistor makes a better switch than a relay.

Impedance and AC Analysis I

The purpose of this lab is to analyze and study a real inductor.

Procedure:
We start with a real inductor connected in series with an external resistance.
2 Multimeters are taking measurements.

We measured R_L = 8.3 Ω
R_ext = 67.2 Ω
We measure our V_rms = 5V at 1000 Hz.

The built circuit

V_in,rms = 4.93 V
I_in,rms = 65.0 mA 
The voltage reading differs from the FG because internal resistane drop 0.7 V
V_in/I_in = Z_L = 75.8 Ω
Z_L = sqrt((R_ext + R_L)^2 + (ωL)^2)
ω = 6280 rad/s
L = 1.16 mH

Adding a capacitor to cancel inductance impedance
1/ωC = ωL
C = 1/(ω^2*L) = 2.19 *10^-5 F

Remodified circuit

V_pp, CH1 = 1.5V
V_pp, CH2 = 20mV
deltaT = 0.4 ms
Phase difference = (deltaT) *6240* 360 ° = 184.32 °

Analysis:

Frequency (kHz)	V_in (V)	I_in (A)	|Z_in| (Ω)
5	4.6	0.073	63.0137
10	4.2	0.0719	58.41446
20	3.51	0.0691	50.79595
30	3.51	0.0653	53.75191
50	4.5	0.0558	80.64516

Questions:
1. It is not the largest at 20 kHz as we used 1 kHz for calculations. Largest current should be at 1 kHz as imaginary part cancels out.

2. V_L = Z_L/Z*V_in
V_L = 2.8574 +  1.2737i
Phasor = 24.0243 °

3. The circuit looks more inductive as imaginary part is always positive.

4. The circuit looks more inductive as imaginary part is always positive.

Conclusion:
The experiment was successful; however, the answers to the questions may not be as expected as it assumes the capacitor was calculated at 20 kHz instead of 1 kHz.