Modular Clock Kit

Build a functional digital clock

fletcherpaul79

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Description

This is one of several kits I have that teach the hobbyist 'basic' digital electronics.
I am still working the bugs out of this.

Details

The Decimal Counting Unit or DCU can be modified for 24 hour format

The logic module contains the wave shaper and divide by 60 circuit for line frequency timing, seconds count, set control, divide by 6 for tens minutes and 13th hour reset and simple power supply.

I use point to point wiring to retain the spirit of 'home brew' building.

I worked out the remaining bugs this month.

I will be posting some additional photos soon.

Components

4 × SN7441 1-of-10 decoder
4 × SN7490 decade counter
2 × SN74393 Dual binary counter
2 × SN7420 Dual 4-input NAND gate
1 × SN7408 AND gate

View all 17 components

Build Instructions

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1

Step 1

The size of the DCU protoboard is determined by the type of display you want to use.
If you want to use the 0.6" LED display you will need additional room for the current limiting resistors.
2

Step 2

The DCU is programmable via the header plug assembly.
By using the external reset test point and moving the header plug from DCU to Clock, the DCU becomes a modulo 6 counter.
3

Step 3

Parts placement is not critical.
However the parts should be placed so there is minimal wire lengths between the I.C.s and header plug.