Electrical Switches; BJTs, MOSFETs, and Relays

MOSFET usually come in a TO220 package.

Relays are often sold as plastic potted boxes with leads extending from one side.

BJTs often come in a TO92 package but can sometimes be packaged as TO220

On circuit breakers, light switches, and kitchen appliances, opening or closing an electrical contact is a mechanical action bringing together pieces using an applied force to bring together two conducting pieces of material. In electronics these days, opening or closing an electrical contact is often accomplished with transistors or relays. 

For transistors, the bipolar junction transistor (BJT) or metal oxide field transistor (MOSFET) are popular options. In years past, uni-junction transistors were used for switching applications but have now become less popular. Transistors pop up mostly in small electronics while relays are most often used for larger electrical loads with current draws beyond a few mA.

When designing a device that incorporates electrical switches, it is important to understand the application in order to pick the best device to engage your circuit. In the teeny tiny operations of a microchip, billions of microscopic BJT transistors are etched on a silicon wafer. Whereas, a much larger BJT (on the scale of inches across) might be used to engage the power sent to an induction cooker. Both these applications rely on the BJT concept although the BJT designed for the purpose is wildly different. Similar stories can be told for MOSFETs and relays that are sized for the application.

Jigsaws, Woodchucks, and O-rings

Although East Campus did not have a Resident Exploration (REX) week this year, I managed to find myself with some work that involves cutting wood. No roller coasters or rides of that sort. This woodwork involved some jig saw and miter saw work. I have been thinking about getting back into my own projects a bit more.

Look closely and see a lil woodchuck

Learned how to refit a o-ring on some glassware since this one wore out.

 

Out in the Fells this Weekend

 

Instead of driving out to New Hampshire, the Cedar St friends decided to hike closer to home and visited the Middlesex Fells reservation. We drove out to a roadside parking spot near Melrose, MA, and disembarked for the rock circuit trail. I used the Jeep to pull up on a berm to keep some distance from the other cars. It was funny to get out of the Jeep since we were up at a 30 degree angle. It was an enjoyable trek and we climbed a variety of rocky outcroppings. I was able to snap a few photos of the Boston skyline while up there. I noticed the Encore hotel and casino facing us in the distance. It was a good reminder to get out more often. The air was fresh and crisp even though we wore our face masks when crossing the paths of other hikers. Fall is definitely here now.

Sitting in my Chair

 

What a wonderful weekend here at 37 Cedar St. The whole gang of five was briefly here before one left to meet their partner. Yesterday I saw Ally when I dropped off a bike for her to use. We were able to socially distance our transaction. She is living on campus since her research obligations require it during these odd times with COVID. I am privileged to get COVID tests through MIT for my connection to the NRL. Tomorrow I will getting tested again before visiting the facility later in the week. Work at PSI is going well and I am learning a lot of new things from my coworkers. I found out that one of my colleagues is familiar with the great bakery Bova's in the North End since they live over there. I miss visiting places like Bova's. 

The bike I fixed up for Ally

the skyline from Tufts University

Sitting in my chair 1

Sitting in my chair 2

Sitting in my chair 3

Sitting in my chair 4

Learning Morse Code with Google's Learn site

 

It can be hard to get into a new hobby especially when there is a lot to learn and the learning slope is steep. I am learning more about amateur radio systems and the licensing process. One facet of the licensing process is a test. In previous years, the test included an evaluation of Morse code. This requirement is no longer necessary however the practice can be helpful in understanding some simple, analog transmissions found on the air (OTA). 

I looked online and found a nice, clean way to learn Morse code.

Check out https://morse.withgoogle.com/learn/

Book Review: For Whom The Bell Tolls

 

I recently picked up another Hemingway novel which I carried with me during the move to Boston. I appreciate his work because he follows a simple yet essential principle in writing good fiction; write from one's own experiences. In this novel, Robert Jordan is an agent in Spain sent to blow up a bridge at the start of a major offensive in the Spanish Civil War. Through a wild variety of experiences, meetings, and events we see how Robert's perception of the people and history of the land has changed.  

Hemingway himself spent a good amount in Spain during the war and began writing about it shortly after returning. As a reporter, he saw the worst of the ways in war. This tales appear to be projected into the characters of this novel and provide a sort-of second hand image of Hemingway's own experiences. 

One particularly interesting facet of the writing style in this novel is the way Spanish and English are used interchangeably at times during dialogue between Robert and his fellow guerilla fighters. Hemingway knows that certain phrases and emotions unique to the Spanish way of speaking are hard to convey exactly as they are in English. 

10/10, would recommend highly

Homemade Grape Juice

 

The grape juice was tart. The concoction lacked any significant sweetness in it. This was partially due to the fact that the drink had no added sugar. Beyond that, the solution was cloudy even though I filtered it through a paper sieve. I ran over to campus from my apartment in Boston. The wind sucked. All the way across the bridge my hat was down. Some other people did not care about the wind. They basked in it. Some people were on boats in the Charles. I suppose it's hard to get sick in a boat. Campus was mostly devoid although a few souls walked about on Amherst alley. I saw a bunch of PODS by McCormick Hall. These PODS likely hold the personal belongings of those who moved out last March, some of those people are returning. The grapes were growing in the garden by Next House that I help water and tend. I think some of the other gardeners don't care that much anymore as their plants are left to go fallow. I gave a homeless man some of the tomatoes I picked. I could not tell if they cared at all. I think they probably did not like tomatoes that much. Perhaps? Another man asked me for a light, I did not give them a tomato since I don't think that would have helped. I think I could make a mean grape juice with these wild grapes.