The intent of this project is to re-create and improve upon the work of the orignal creator, the YouTube channel @electrarc240. The result was a recreation of the efforts as outlined in the video series found here:
ElectrArc240 - Circuit Design Tutorial
Decimal time, also known as metric time, operates on a base-10 (decimal) time system rather than the traditional base-60 (sexagesimal) system we use for measuring time (i.e., 60 seconds per minute and 60 minutes per hour). In decimal time, the day is divided into 10 hours, each hour is divided into 100 minutes, and each minute is divided into 100 seconds. This results in a simpler, evenly divided system that aligns more closely with the decimal (base-10) system we use for most other measurements.
The decimal time system was proposed and briefly used in France during the late 18th century (around 1793–1795), as part of a wider push to implement the metric system across all areas of measurement. It was largely abandoned after a few years because the traditional system was more deeply ingrained and easier to use for most people.
Key Features of Decimal Time:
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A decimal day is still the same length as a traditional day (24 hours), but the units within the day are divided differently
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Decinmal Day = Divided into 10 decimal hours.
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Decimal Hour = Divided into 100 decimal minutes. It is equivlaent to 2.4 traditional hours.
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Decimal Minute = Divided into 100 decimal seconds. It is equivalent to 1.44 traditional minutes (or 86.4 traditional seconds).
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Decimal Second = A decimal second is slightly shorter than a traditional second (0.864 traditional seconds).
Decimal Time is mostly theoretical or used in specific experimental or educational contexts. It can sometimes be found in scientific or computing environments where a more uniform system of measurement is desired.
The Decimal Clock is an IC based clock that continuously counts the days, hours, minutes, and seconds from the time it is reset. It wil count from day zero to day seven at which time it will reset itself back to zero and begin it's count again. In it's current form, the user will have to manualy set the time by hitting the reset button on Sunday evening local time, at the turn of midnight.
A 4 MHz oscilator forms the basis of the clock circuit. The signal generated by the oscilator is first passed through a 4020 binary counter/divider IC (U1) where it is divided by 10800 at outputs Q5, Q6, Q10, Q12, and Q14. The outputs are passed through a SN74LS11 3-input AND gate IC (U3) which is used to reset the 4020 IC when a specific value (10800) has been reached. This reduces the 4 MHz clock signal down to 370.37 Hz. This reduced clock signal is then fed into a second 4024 binary counter/divider IC (U2) where it is divided by 32 at output Q5. This reduces the frequency of the clock signal down to aproximately 11.57 Hz. This frequency correlates to an 86.4ms duration which is the length of time of a decimal second.
The clock signal output of the 4024 is fed into the first of seven, cascaded 4026 decade coutner/divider IC's (U5, U7, U9, U11, U13, U15, and U17). These IC's are used to drive coresponding seven segment LED displays. The first IC (U5) of the cascade drives the Least Significant Digit (LSD) of the clock. The 4026 IC counts the pulses coming in to pin 1 and displays the totalized value to the LED display. Once the count reaches "10" (0-9) the 4026 sends a pulse out the "carry out" pin 5 then resets and begins the count again. The carry out pulse is then used as a clock input for the next 4026 in the cascade (U7) where a similar action is performed. This continues on through the cascade to the seventh digit (U17), the Most Significant Digit (MSD). The value of the MSD is the day of the week.
The clock contains two reset circuits. An automatic reset for Most Significant Digit (MSD) and a manual reset pushbutton for ALL digits.
The MSD (day counter) automatic reset circuit will send a pulse to the MSD 4026 IC (U17) reset pin once the seventh day of the week is reached. The reset circuit utilizes a three input AND gate (U3C) to monitor two conditions to set the reset pulse. The first is U17 CARRY OUT not true and the second is a bit derrived from an NPN transistor (Q2) that monitors the "F" segment output of U17 for NOT TRUE. The third input of the AND gate is tied to +5v. The output of the AND gate is used to reset the MSD.
The manual reset is a push button used to set the time of the clock. This works by sending a pulse to all 4026 reset pins (U5, U7, U9, U11, U13, U15, and U17). The manual reset circuit will pulse the MSD (U17) through a 1N4148 diode (D1). The diode prevents the MSD automatic reset pulse from back feeding into the manual pulse circuit and resetting the remaining digits.
The CD4020 is a 14 stage, ripple-carry binary counter. The counter stages are master-slave flip-flops. The state of the coutner advances on the negative transition of each input pulse. A high level on the RESET line resets the counter to an all zero state. Counter outputs Q2 and Q3 are omitted on this IC.
The following video provides an overview of the functions and capabilities of the 4020 and 4024 IC:
https://youtu.be/QmvfDinq0QI?si=iYM-AZGnyLCsgtye
The CD4024 is a 7 stage, ripple-carry binary counter. The counter stages are master-slave flip-flops. The state of the coutner advances on the negative transition of each input pulse. A high level on the RESET line resets the counter to an all zero state.
The CD4026 is a 5-stage Johnson decade counter and an ouotput decoder which converts the Johnson code to a 7-segment decoded output for driving a one stage is a numerical display. The CD4026 is designed for use with a 7-segment, common cathode LED display.
The following video provides an overview of the functions and capabilities of the 4026 IC:
https://youtu.be/HuVM-GvXMK8?si=anxqkpNL1QQRIXNr
The CD4069 is a 6 circuit inverter IC.
The following video provides an overview of the functions and capabilities of the 4069 IC:
https://youtu.be/krzgrWj5j9g?si=euBiHwWfCx5YfokL
The SN74LS11 consists of three independent, 3-input AND gates.
The following video provides an overview of the functions and capabilities of the 74LS08 which is similar to the SN74LS11 IC but contains 4 gates instead of three:
https://youtu.be/SqQWDvRWeUA?si=IybF3-gupXK9ZKyV
The Decimal Clock © 2024 by Red Chair Labs is licensed under Creative Commons Attribution-ShareAlike 4.0 International.