Tag Archives: electromagnetics

DC-DC switching voltage regulator: Buck converter

Power MOSFETWhen I took a power electronics course at MIT (6.334) almost two years ago I instantly fell in love with the simplicity and ubiquity of switching power supplies. They are so simple and interesting that I decided to devote a few posts here describing how they work. Voltage regulators are interesting and useful to learn about because they are used everywhere. Electronic components (for example, those within your home electronics equipment) often require different voltages, so voltage regulators included in the equipment to generate those voltages. The first question to answer in this post is “What is a voltage regulator”: Continue reading DC-DC switching voltage regulator: Buck converter

Coil Gun Results and Explanations

Several months ago when describing how the build the coil gun, I mentioned that I would explain some of the “extras” that we implemented in our coil gun project. I will explain the mounting brackets and the opto-interrupters here, as well as why a coil gun works.

How it works
When a current flows through a coil of wire a directed magnet field is induced inside that coil proportional to the current. After the capacitor is fully charged we discharge the capacitor into the coil. This provides a large current in the coil thereby inducing a strong magnetic field. The projectiles that we use are made of steel which contains a lot of iron, a ferromagnetic material. The magnetic field in the coil aligns the magnetic moments in the iron which makes the iron attracted to the center of the coil. The brief discharge of the capacitor finishes before the projectile reaches the middle of the coil so the projectile continues instead of stopping in the middle of the coil. Continue reading Coil Gun Results and Explanations

Simple Coil Gun

Barrel of the coil gunThe next project that I’ve been working on (with a lab partner) for my electromagnetics course is an “EM Buffet Lab.” In other words, we get to choose what we want to build, as long as it is EM related, and then do a write-up about why and how it works. What my lab partner and I are building is a coil gun. We have actually already finished it, but we are still preparing our presentation and report for Wednesday.

Note: Be sure to also read the follow-up post to see the projectile velocity and some other goodies.

What is a coil gun?
A coil gun uses a solenoid (coils of wire wrapped closely together) to create a magnetic field. This magnetic field attracts a ferromagnetic material during a strong, brief current discharge (usually produced by a capacitor.) The projectile wants to go to and stay in the middle of the solenoid due to the induced magnetic field, but by the time the projectile gets to the middle of the coils, the capacitor is fully discharged and no magnetic field exists anymore. Therefore, the projectile does not stop, but continues traveling through the solenoid instead of stopping in the middle of it. Continue reading Simple Coil Gun

Junkyard Generator – update

My group and I have finished our junkyard generator. Here is an overview of what we did (click on the images below to go to bigger versions of them):

The frame was initially made out of steel. Sherman did a good job with this (I will try to get a picture of it to put here.) We quickly discovered that the magnets in the generator had too much of an attraction to the frame and made spinning the axle very difficult. Chad then made the frame out of wood. Continue reading Junkyard Generator – update

Junkyard Generator

I am taking an electromagnetics course this semester, and our first project is getting into groups and making a human-powered generator that can light a bulb. It is actually a pretty fun project. We have to use “junk” that we find, and can spend no more than $10/person in the group. There are 5 people in our group, so I don’t think the money specification limits us very much. So far it looks like we will spend a total of $5 (for the entire group, not per person.)

Here are some interesting and useful tidbits we have learned so far: Continue reading Junkyard Generator