DE Unit 7: The Birthday Problem

Follow the Circuit Design Process to create a date-displaying circuit


 Download the Birthday Problem Assignment

As we start our second semester here in Digital Electronics, we’ll be tackling “The Birthday Problem”.  When it comes to digital electronics challenges, this problem is one of the best.  It will require that you review some of the essential parts of last semester’s work as you create a circuit to display your date of birth. As you design and build your own Bug Bot, we’ll go through three major steps:

  1. Review the main ideas from first semester including displays, binary counting, truth tables, K-mapping, and AOI/NAND/NOR circuit design
  2. Design, simulate, and build your circuit using the same procedures we practiced last semester
  3. Learn how Programmable Logic Devices (PLDs) work and upload your birthday problem circuit to your PLD to get it running!

When you’re done, you’ll have worked with all the key elements of digital electronics to complete a complex circuit


(10 pts)  About 2 days

The circuit design process is used to take a complex situation or problem, reduce it to a binary numerical situation and truth table, and then develop a working circuit to solve the problem.  To get rolling on this problem, we’ll need to review the key ideas from first semester!


(50 pts)  About 5 days

In the second part of the unit, you get to design a circuit that will display the parts of your date of birth in order as switches count in binary from 000 to 111.  You’ll start by planning out the circuit by hand in your notebook, then building in Multisim and breadboarding as always!


(10 pts)  About 2 days

Finally, we get to learn how Programmable Logic Devices (PLDs) can be used to simplify the circuit design process.  We’ll find that PLDs like our own CMODS6 chips can be used to upload entire Multisim circuits and make breadboarding a breeze!

 Download the part 1 rubric!

 Download the part 2 rubric!

 Download the part 3 rubric!

PART 1: Review

Displays, Binary, Truth Tables, K-Mapping, AOI, NAND/NOR

Circuit Design Process

Our job of creating a complex circuit to display a birth date as we count in binary requires that we remember some important information from last semester.  In this first part of the unit, you should take a couple days to review the big ideas from six main topics: 7-segment displays, binary counting, truth tables, k-mapping, AOI design, and NAND/NOR design.  You can review your notes, talk with your classmates, and review some of the videos/presentations linked from last semester.  Take good notes to remember how the circuit design process uses these tools!


 Review the Circuit Design Process once again.  Copy the Circuit Design Process into your engineering notebook and think about what we did last semester at each step!

 Take a full page of notes to review 7-segment displays, binary counting, and truth tables.  Try to include some simple examples as you look over your notes and resources from first semester.

 Take a second page of notes (2 in total) on K-mapping, AOI circuits, and NAND/NOR circuits.  Try to include some simple examples or pictures to remember what those different tools do for us.

7-Segment Display Review

Binary Counting Review

Truth Table Review

K-Mapping Review

AOI Design Review


What’s Due In Birthday Problem Part 1: Review

  • Circuit Design Process Notes
  • Review Notes Part 1
  • Review Notes Part 2
  • Benshoof’s Check-Off

Here’s what’s due in Part 1: Review

  1.  Draw the Circuit Design Process into your engineering notebook
  2.  Take 1 page of notes on the first three review topics
  3.  Take 1 page of notes on the last three review topics
  4.  Have Benshoof check-off your review notes

PART 2: Plan, Simulate & Build

Create, simulate, and breadboard your birthday circuit

The second part of our unit is where the majority of your time should be spent.  As you get started, your job is to think about your birth date in the from “MM-DD-YY”.  If we count all 6 letters and both dashes, that gives us a total of 8 characters for our circuit to display.  What your job is, is to follow the circuit design process and the example problem setup to create a circuit that can use switches to count in binary from 000 (0) to 111 (7), and with each of those eight digits, display each of the digits in your birth date.  Once you’ve planned your circuit, we’ll Multisim and Breadboard to get it all working!

Birthday Problem Challenge Overview

Example Birthday Problem Truth Table Setup

Example Completed Breadboard

What’s Due In The Birthday Problem Part 2: Plan, Simulate & Build

  • Plan Expressions
  • Plan/Draw Circuits
  • Simulate Birthday Circuit
  • Breadboard Birthday Circuit
  • Benshoof’s Check-Off

Here’s what’s due in Part 2: Plan, Simulate & Build

  1.  Follow the Circuit Design Process to make a truth table, K-Map, and simplified expressions for your birthday circuit
  2.  Draw out your AOI/NAND/NOR circuits for each segment in the 7-segment display
  3.  Build your complete circuit in Multisim and confirm that it works as intended
  4.  Breadboard your complete circuit carefully and confirm that it works as intended
  5.  Have Benshoof check-off your written circuit, successful simulation, and breadboard!


Programmable Logic Devices and Multisim

Multisim PLD Reference

In the last part of this unit, we’ll take some time to look at Programmable Logic Devices (PLDs).  The PLDs we use are called “CMOD Chips” and are actually Digilent CMOD S6 Chips.  They work kind of like Arduinos in that they have a lot of pins that we can identify as inputs or outputs as we see fit. The cool thing about them is that we’ll be able to take circuits designed in Multisim and upload them directly to the board.  Then, instead of breadboarding a lot of IC chips, we can just wire the switches and LEDs to the CMOD chip and let it do all the work!  We’ll practice by getting our birthday circuit working on the CMOD chip.

BONUS:  Check out the Super Secret Bonus video below for essential Multisim pro-tips!

PLD Overview

Example of using PLD mode in Multisim

* Super Secret Bonus Logic Converter Tutorial *

What’s Due In The Birthday Problem Part 3: PLDs

  • PLD Notes
  • PLD Tutorial
  • PLD Birthday Circuit
  • Benshoof’s Check-Off

Here’s what’s due in Part 3: PLDs

  1.  A page of notes on PLDs, their use, and the corresponding tools in Multisim
  2.  Complete the PLD Tutorial and make a super-simple PLD circuit
  3.  Transfer your Birthday Problem circuit to the PLD and get it breadboarded successfully!
  4.  Have Benshoof check-off your finished PLD birthday circuit

Double Check: Unit Expectations

Check what you need to have completed by the unit deadline

The purpose of this unit is to review the elements of the Circuit Design Process from first semester and combine them to design, plan, and create a complex circuit.  Here you’ll complete “The Birthday Problem” where your finished circuit is able to use binary counting to display the digits in your birthday.  You’ll get more practice with Multisim and breadboarding before learning about PLDs and how they can make the digital electronics process much quicker.

Engineering Notebook:

 (Part 1) Notes on Circuit Design Process

 (Part 1) Review notes on displays, binary, truth tables, k-mapping, AOI, and NAND/NOR logic

 (Part 2) Notes from designing your birthday problem circuit including your truth tables and k-maps

 (Part 2) Drawn AOI/NAND/NOR circuits for completing your birthday circuit

 (Part 3) Notes on PLDs, their use, and the associated tools in Multisim

Building & Making:

 (Part 2) Multisim your birthday circuit and confirm it works as expected

 (Part 2) Breadboard your birthday circuit and confirm it works as expected

 (Part 3) Complete the simple PLD Tutorial

 (Part 3) Transfer your birthday circuit to the PLD module and breadboard

Benshoof Checkpoints

 (Part 1) Benshoof should have seen your review notes

 (Part 2) Benshoof should have seen your Multisim birthday circuit

 (Part 2) Benshoof should have seen your Breadboarded birthday circuit

 (Part 3) Benshoof should have seen your finished PLD Circuit