Testing part

The assembly of the launcher was completed following the initial design, but this proved to be unsucessful as the frame was unable to hold the magnets due to their strength. This lead to the launcher frame being redesigned.
The new launcher frame was constructed, but there was another problem with the rails. The copper tubing that was used as the rails was not strong enough to hold the steel ball bearing in place. The steel ball was attracted to the magnets and would be pulled through the copper rails, bending them out of the way. The copper rails were therefore replaced with steel rails.
This new design held the ball bearing and the magnets in place without any problems.
The circuit was then able to be connected to the rails to test the launcher. There were initially problems with the ball bearing being caught in the magnetic field and being troublesome to move mechanically, let alone under firing.
After some testing, it was decided to swap the steel ball bearing for an aluminium slug. This gave better conduction with the rails as there was a larger contact surface, as well as being lighter than the steel ball bearing. More importantly though, not being attracted to the magnets meant that the aluminium slug could move freely along the rails.
Still however, the slug was unable to launch. It was decided after much testing that the reason was that our capacitor(s) weren't delivering enough power. To further test the launcher we used a borrowed capacitor array of 0.2 Farads, at 4v. This was a vastly greater amount of power than we had tested with. Still however, there was no movement. It was decided that the inertia of the slug was too great and that the slug would have to be already moving to actually fire. With further development, the launcher would have an integrated injector, allowing the slug to being introduced to the magnetic field and to the rails with enough momentum to allow the bullet to be launched.

Project Component

figure.1 Components

figure.2 Magnets and rails

As can be seen in the picture,the magnets are setting in parallel while the two rails are settled in between. Once the edge of the rails are powered by the current, the current through the bullet would trigger the object to move as a result of Lorentz force. Theoretically, the bullet could attain a velocity of 1 m/s. 

figure.3 Sensor circuits

 The sensor part include two individual circuits, the circuit at the top of the picture is a basic LED circuit and the circuit at the bottom is an amplifier circuit.

figure.4 Charge up circuit

figure.5 magnets 

The second meeting

figure.1 simulation of charge up circuit

figure.2 output of the current

As were shown in the pictures above, a DC power source of 16 volts is assembled in the LHS and a capacitor of 100uF is in parallel with a resistor of 1ohm. In this case, the resistor is on behalf of the magnets which we had mentioned. Once the capacitor is charging to 16 volts, it is essential of obtaining the current once the switch on the RHS is on. With respect to figure.2, it is presented the current is starting to decline after 3ms and it is due to the transient phenomena regarding the capacitor & resistor circuit.

figure.3 simulation of the photo diode

figure.4 output voltage of amplifier

As can be seen in the figure.3, two standard photo diodes are connected to a bipolar transistor individually. Specifically, the common-emitter transistor is treated as an amplifier in order to detect the voltage fluctuation concerning the output side. Two capacitors which located at the base part as well as the output side were aiming to filter the DC voltage source. As a result, the input AC signal should be amplified and detected at the output side of the transistor.

First Group Discussion ( the parameters)

As has been mentioned before,the basic principle of this project is energy transformation.




The C in the LHS is the capacitance in the circuit and the V is the voltage across the capacitor. In regard to the RHS, the m stands for the mass of the bullet while v is the velocity. Initially, we assume the velocity of the bullet as 1m/s. Furthermore, the safe voltage is defined as 16 volts and the mass of the bullet is assumed to be 12 grams approximately.Therefore,the value of the capacitance can be obtained according to the equation.


Nonetheless, the capacitor with 100uF capacitance is finally applied because of the safety consideration. With respect to the charge up component, an AC power supply is connected to the capacitor in series. Assume the resistance in regard to the load is 1 ohm, and the current across the rail is 16A.

Basic principles of miniature launcher

The basic principle of miniature launcher is energy transformation which intend to transform electrical energy to kinetic energy.

As has presented in the picture above, our supervisor explained the principles and specific parameters during the first meeting. Firstly, a capacitor or several capacitors are employed for supplying current and DC resources are using to charge up the capacitors.The following part is the magnet together with the rails which used to send bullet.Once the current pass through the rails, the bullet will start to move as a result of Lorentz force.After that, two photo diodes as well as LED are installed for measuring the actual velocity of the bullet.Specifically, a amplifier circuit is linked to the photo diode and once the bullet detect the lights from LED, it is expected to obtain a distortion of pulse in the output side of the amplifier.In that case, the distance divided by the time between the two expected distortion of pulse is, theoretically, the actual velocity of the bullet.In general, the entire circuit should be assembled in a box and three switches are necessary to be applied.