Can a simple circuit translate a number you press on a keypad into binary coded decimal (BCD) output? You build a circuit using CMOS logic gates that reads input from up to 16 switches. Each key press produces the matching BCD value on four output lines.
A memory module can be added so the output stays visible after you release the key. LEDs show each BCD digit, though they are optional. The circuit runs on 5 to 15 volts DC.
You assemble everything on stripboard using basic tools. A drill bit can cut the copper tracks by hand if you do not have a dedicated track cutter.
Hypothesis
The hypothesis is that a circuit can be constructed to convert a hexadecimal number to a binary coded decimal number.
Logic gates are tiny switches inside circuits that make yes-or-no choices based on their inputs. In this project, CMOS logic gates read signals from up to 16 switches on a keypad. When you press a key, each gate checks its inputs and produces a yes-or-no output — and together they convert the key press into matching binary coded decimal values on four output lines.
An electric circuit is the path that lets power flow from a source through wires to run things. In a hexadecimal-to-BCD converter, that path runs on 5 to 15 volts DC. When you press a key on the keypad, the circuit reads the input through CMOS logic gates and produces the matching BCD value on four output lines.
Method & Materials
You will construct a circuit with switches, LEDs, and a memory module. You will also need to cut tracks and make links.
You will need a keypad, CMOS 'AND' gates, resistors, LEDs, and a memory module.
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The experiment was successful in constructing a circuit that can convert a hexadecimal number to a binary coded decimal number. The most interesting observation was that the circuit can be extended to 16 keys to give the full hexadecimal to binary coded decimal conversion.
Why do this project?
This science project is unique because it shows how to construct a circuit that can convert a hexadecimal number to a binary coded decimal number.
Also Consider
Experiment variations to consider include using different types of switches and memory modules, and using different voltages.
Full project details
Additional information and source material for this project are available below.
