Mutual Inductance in Multisim

For over a year, I have used National Instruments' circuit analysis and design software: Multisim. I have v12, educational version.

Our current homework is about mutual inductance. In class, we received a quick demonstration on how to do couple inductors in v13:

  1. place your inductors, but remember the dot's location is on the left of the inductor when you first place it, so rotate it to position the dot elsewhere
  2. under "Transformer," choose COUPLING_INDUCTOR and place it off by itself, as it is not connected to your circuit
  3. open that element's properties (Ctrl+M)
  4. under "Value," fill in the fields "Coupled inductors list" (by name, like "L1,L2") and "Coupling coefficient"
  5. finish your circuit

However, once I got home, I couldn't find COUPLING_INDUCTOR, rather COUPLED_INDUCTOR, which is not the same. The Help for v12 says COUPLING_INDUCTOR exists, but it apparently does not, perhaps an intentional omission in the academic version. Eventually I got a v12 file with a COUPLING_INDUCTOR element from someone else, so I've been using that file as the template for my assignments. It was very aggravating to learn that cutting and pasting the element into a new file resulted in a netlist error.

One thing I've done is mark the mutual inductance dots by using colored asterisks placed as text. Multisim seems not to offer a way to display the dots, so that is my solution.

This is what COUPLING_INDUCTOR looks like:


I did write National Instruments about the netlist errors I kept getting when trying to link inductors before receive the COUPLING_INDUCTOR from someone. Their technical support should get back with me Monday.

Up/Down Timer Circuit Video

Here's a short movie of the timer circuit that I designed in Altera® Quartus 9.1 Web Edition. I downloaded it to the Altera USB Blaster FPGA (with a Cyclone II chip) to demonstrate it for my class. The video was shot with my iPod, so it is not very smooth.

It took me some time to edit and format the video: I had never before used iMovie or uploaded anything to YouTube. The current guidelines YouTube provides for exporting content from iMovie are clear.

It took too long for the initial iMovie-export QuickTime version to load, so I chucked it.

Timer Circuit

The other day I completed the final project circuit for Digital Fundamentals, EECT112. This is my first real electronics course, so it has been difficult; most of the other students have had other courses before.

When presented with a choice for the final project, I chose to make a time with seven-segment LED display. Originally I thought to have just a three-bit input that would count down, which would require that I learn better how to perform subtraction with circuits. In the end, I used counter ICs, since I began to run out of time for the initially quite complex task I had set for myself.

My timer has an SR flip-flop to reset the counter; the two counter ICs (for two four-bit BCD input) output a high to signal that the maximum up- or down-count has been reached. I used that to reset the flip-flop so the counter would not loop. There are LEDs that signal whether the timer counts up or down and whether it is currently counting.

When one holds down the push button, throwing the switches causes the seven-segment LEDs to show changes. Releasing the button starts the timer.


The hardest part of the project was the clock. I tried to use the FPGA's 50MHz clock and divide it down by 50 million, that introduced too much propagation delay. An external clock--an oscilloscope, actually--was my savior.

This was a neat project, but I wish I could have done it in VHDL, since using the schematic capture of Quartus can be problematic.

Altera Code Samples

For my Digital Fundamentals course, we use an Altera FPGA with a Cyclone II chip on it. My final project is to build a timer, which I want to set with 4-bit binary input from switches; the decrementing seconds should got to 7-segment LEDs. I've been searching about and found that Altera provides plenty of source VHDL code to start with.

Thank, Altera!

Today in EECT112

Today was our second exam, which was split into two parts: test and lab. It was heavy on Boolean logic, with reduction, Karnaugh maps, and symbolic designs. Plenty of questions about the rules of Boolean logic and using NOR and NAND to make other gates.

We also received paperwork about our projects, which constitute 13% of our grade. I need to think about what I want and can do with my circuitry knowledge. I like the ASCII to 7-bit display, but a timer would be neat, too.

Programming an FPGA

Last Tuesday in my "Digital Fundamentals" lab, we wrote up a Boolean logic equation involving an AOI. In Quartus, we drew the equation as a schematic and wrote the VHDL. After compiling, creating the waveform, and running the simulation, we attached an FPGA through a USB cable to program it.

The design was to send a high signal for odd numbers to 9. We thus wired switches to be thrown as binary values. If odd, up to 9, an LED came on. Not terribly complex, but from small things come greater things.

Volta & MacSpice

This evening I cracked the textbook, Digital Electronics: A Practical Approach with VHDL, for my coming EECT 112 Digital Fundamentals course. The course will require working with some Windows software, but I did a little seeking for Mac options. I found MacSpice and Volta, which is for analog circuit analysis. All I've done is download them, since it's late and I have work tomorrow morning.

If I can essentially do what I did with PSPICE, that would be neat.