With Thanksgiving almost here, you might still be deciding what “go-to” dish to serve. When it comes to deciding to serve a Thanksgiving turkey, the decision between stuffing and dressing is always a difficult one.
- Having all the juices from a brined turkey roasted into the stuffing while it cooks is a flavor that cannot be beat. Here, stuffing functions as a vessel to infuse flavors into the turkey in addition to accompanying it.
- However, the taste is optimized by dressing, cooking each section of the bird individually according to its own unique temperature and time. Also, dressing prevents overcooking the bird while waiting for the stuffing to reach a safe 165 degrees.
Dr. John X. Wang’s book titled “What Every Engineer Should Know About Decision Making Under Uncertainty” discussed how engineers would flip coins to facilitate decision-making under uncertainty.
Shall we flip a coin to decide? Yes, and we will do it electronically to assure the reliability of flipping a fair (unbiased) coin. In this Risk Engineering project, to facilitate our decision making under uncertainty, we will build an electronic circuit to flip a coin.
How to flip a coin electronically?
As shown by the schematic, the electronic circuit has three sections:
- One square-wave oscillator
- One JK flip flop, and
- Two LEDs:
- Red – Stuff It
- Green – Dress IT.
The circuit uses CMOS digital ICs and MOSFET transistors (Note: the schematic does not show the power and ground connections for the ICs). When powered from a 9V battery both LEDs will light. When you press the switch, one LED shuts off and the other stays lit; but which one? There’s a 50-50 chance for either color – a perfect fair coin.
The square-wave oscillator uses a NAND gate. Digital signals are either high (+V) or low (0V). The output of a NAND gate will switch between high and low depending on its inputs defined by the truth-table for a 2-input NAND gate. The switching frequency is determined by the RC time constant tau (T). T = R1 × C1. Pushing the normally open Switch shorts the input to ground and stops the oscillation.
For the JK flip-flop, when J and K are both held high, the outputs will toggle each time a pulse is applied to CLK. Toggle means to go to the opposite state. If it was high, it goes low. If it was low, it goes high.
MOSFET transistors function as drivers for the two LEDs: Red (Stuff It) and Green (Dress It).
For electronic assembly, you may reference Dr. John X. Wang’s book titled “Green Electronics Manufacturing: Creating Environmental Sensible Products.”
Now we are equipped with an electronic circuit to help our decision-making about Thanksgiving Meal.
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