Tuesday 9 December 2014

German Chocolate Cake

  • 4 oz. (1/2 cup) unsalted butter, softened; more for the pans
  • 4 oz. semisweet or bittersweet chocolate (up to 70% cacao), coarsely chopped (about 1 cup)
  • 1/2 cup boiling water
  • 9 oz. (2 cups) unbleached all-purpose flour
  • 1 tsp. baking soda
  • 1/2 tsp. table salt
  • 4 large eggs, at room temperature
  • 2 cups granulated sugar
  • 1 tsp. pure vanilla extract
  • 1 cup buttermilk, at room temperature
7 oz. (about 2 cups) sweetened, shredded dried coconut
  • 4 large egg yolks
  • 1 12-oz. can evaporated milk
  • 1-1/2 cups granulated sugar
  • 2 tsp. pure vanilla extract
  • 3/4 tsp. table salt
  • 6 oz. (3/4 cup) unsalted butter, cut into chunks
  • 1-1/2 cups pecan halves, toast
    Make the cakes
    Position racks in the upper and lower thirds of the oven and heat the oven to 350°F. Grease the sides of three 9x2-inch round cake pans with butter and line the bottoms with parchment circles.
    Put the chocolate in a small bowl and pour the boiling water over it. Let stand for several seconds and then whisk until the chocolate is dissolved. Set aside until cool to the touch before mixing the batter.
    Sift the flour, baking soda, and salt onto a sheet of waxed paper. Whisk the eggs in a small measuring cup.
    Beat the butter for a few seconds in a stand mixer fitted with the paddle attachment on medium-low speed. Add the sugar in a steady stream and then beat on medium speed, scraping the bowl as necessary, until the mixture is lightened in color and fluffy, 4 to 5 minutes. Still on medium speed, add the eggs a little at a time, taking a full 1-1/2 minutes to add them all. Add the melted chocolate and vanilla and beat just until blended. With the mixer turned off, add a quarter of the flour mixture. Mix on medium-low speed just until incorporated. Add a third of the buttermilk and mix until blended. Repeat, each time adding another quarter of the flour, then a third of the buttermilk, until the last of the flour is added. Scrape the bowl as necessary and mix each addition only until it is incorporated.
    Divide the batter among the pans and spread it evenly. Bake, rotating the pans and swapping their positions, until the cakes just start to pull away from the sides of the pans and spring back when very gently pressed with a finger, 20 to 25 minutes. Let the cakes cool in their pans on a rack for 10 minutes.
    Run a knife or small spatula around the edges to separate the cakes from the pans. Turn the cakes out onto the rack and peel off the parchment. Cool completely.
    Make the filling
    Spread the coconut on a rimmed baking sheet. Bake at 350°F, stirring every 2 minutes, until golden-brown, about 10 minutes. Scrape the toasted coconut onto a sheet of waxed paper and let cool completely.
    Whisk the egg yolks with the evaporated milk, sugar, vanilla, and salt in a heavy-duty, nonreactive 4-quart saucepan. Add the butter. Set over medium heat and stir constantly with a heatproof spatula, scraping the bottom and corners of the pot. When the mixture starts to boil, adjust the heat so that it boils actively but not furiously, and cook, stirring constantly, until golden and thickened, 3 to 4 minutes. Off the heat, stir in the coconut and pecans. Let cool completely.
    Assemble the Cake
    Put one cake layer on a cake plate. Spread a third of the filling over the top of the cake, leaving a 1/4-inch border. Top with a second cake layer. Spread with half of the remaining filling. Put the third cake layer on top and cover it with the remaining filling. Leave the sides of the cake exposed. Serve at room temperature.
    Make Ahead Tips
    The cake will keep in the refrigerator for up to 2 days. Let it come back to cool room temperature before serving.ed and coarsely chopped

Electronic Thermostat

Mechanical thermostat has been around for a long time and has been used in industrial control, home appliances control and many other devices to measure and control the temperature of a certain processes. The sensor used usually is a bimetallic sensor that is make from two different metals that expand at different rates as theThese metal strips are bonded together and when the temperature rises, the strips will bend upward hence making connection to the contact of the circuit so that current can flow through the circuit.
As the temperature cools down, it will go back to its original position and disconnect the current from the circuit. By adjusting the strip and the contact, the temperature can be controlled. Most oven and air conditioners use this type of sensor. The mechanical thermostat is more widely used due to its lower cost compared to electronic type.
The use of electronic thermostat is becoming more popular now as the cost of semiconductor continues to drop with the advancement of better fabrication and packaging processes. Many applications have switched to electronic control as the control of the temperature is more accurate, easier to control the desired temperature using digital technology, more reliable and interfacing with other devices.
This application note from Microchip uses a low cost 6 pin microcontroller in the design of electronic thermostat. The features of PIC10F204 are as shown below. One advantage is that it has the PDIP package which makes it easier for electronic hobbyists to do their own soldering.
256 Words Program Memory and 16 bytes Static RAM
Wide Operating Voltage from 2.0V to 5.5V DC
3 I/O

1 comparator
25 mA source/sink current I/O
Power supply is directly tapped from the AC lines voltage using a resistive based power supply. This makes the entirecircuit live and one has to be careful when implementing this project. Ensure that no parts of the circuit is accessible toany user. Use a plastic enclosure to house the printed circuit board properly.
The principles of triac is briefly discussed here. The use of zero crossing detection is useful as many applications use this method in their operations. Among them are light dimmer and motor control applications.
Learn how to optimise the program code to make it efficient. Many programmers use long routines to accomplish a certain task when a few lines of codes would be sufficient. This experience needs to be learned as one hands on a project and repeatedly look into the code to make it shorter and efficient.
Having learned the code, one can then modify and add temperature sensor to make it a close loop control. Display circuity and user interface can be added to the system by migration to a higher pin count microcontroller.