Purpose:
The purpose of this project was to give a gental introduction to mechatronics. Mechatronics is the combination of mechanical and electrical engineering. For an introduction to mechatronics there couldn't be a better thing to make than a car. Because we didn't know much about mechatronics the car design was simplified by using a fan to power the car rather than a gear box.
Procedure:
We were first told the parts that we would be supplied with. It was up to us to decide what to use for the chasis, wheels, axis and how we were going to adhere both the parts and the circuit. The thing that effect my car the most was my chasis decision. My original Idea was to cut a piece of acrylic but after comparing it to my other chasis idea (a small project box) I decided that the piece of acrylic was too heavy. The thing that I did not consider however was the center of gravity of my car. Even though I made my car lighter by choosing a small project box I focused almost all of the car's weight on one point therefore the car required more power to move such a condensed weight. Because of this the other cars that weighed more than mine went faster than mine because they had better weight distribution.
Circuit Description:
The two main components of my circuit were the LDR and the TIP122. The Light Dependant Resistor either creates more resistance if there is low light for less resistance if there is a lot of light. The TIP122 is two transistors in a darlington pair. The typical role of a transistor is to amplify the current running through it. In this case we need a lot of current to power the fan so we used the TIP122. The TIP122 is special because it has two transistors in a Darlington pair. This means that instead of the current getting amplified once it is now getting amplified twice. Therefore the total current gain is the two individual gains multiplied together. For more information click here.
Realizations and Goals:
After racing my car it was obvious what I had done wrong. I had put all of my car's weight on one area. Because of my car's mass distribution it was unable to accelerate as intended and never maintained speed. Acceleration is affected by the mass distribution. The more condensed the mass the more force required to move the object. If I had have used the acrylic for the chasis of my car I think that it would have been faster. The one correct choice I made however was in regards to my wheels. Without thinking much of it I chose the smallest wheels. At the time I chose them because they suited my car the best but they actually had a positive affect on my car. Because the wheels were so small they had a smaller moment of inertia. Moment of inertia describes how difficult it is to change the angular motion of the axis. It is not just based on how much mass the object has overall, but how far each bit of mass is from the axis. The further out the object's mass is, the more rotational inertia the object has, and the more rotational force (torque, the force multiplied by its distance from the axis of rotation) is required to change its rotation rate. Because I used those small wheels it allowed the fan to move my car. If I had have used bigger wheels I am doubtful my car would have moved at all. For the next project I will be more aware of my weight distribution but use the same wheels I used for this project.
Parts List:
Parts given:
Quantity
|
Part
|
Description
|
1
|
DC Motor
|
4.5V, 32000 rpm
|
1
|
Propeller
|
4-blade plastic
|
4
|
AA Battery
|
|
1
|
Battery Holder
|
|
1
|
LDR
|
|
1
|
Resistor
|
1M Ω, 1/4W
|
1
|
TIP122
|
NPN Darlington Pair
|
Chosen parts:
Quantity
|
Part
|
Link
|
1
|
Project Box
|
|
4
|
Metal axel
|
|
4
|
Wheels
|
