An electronic clock

Figure 1: Diagram of LED electronic clock.

If you have at your disposal in a bottom drawer of the few integrated circuits making up the assembly, you can do the pendulum, which simulates the movement of the pendulum of a clock.
By arranging the ten LED arched over a plate of metal or wood, you get the desired effect.
One LED is lit at a time continuously, from left to right and from right to left, and so on.
The first three inverters IC1-A, IC1 and IC1-B-C content in 7404 are the clock needed to drive the two NAND gates IC2-IC2-A and D present inside the 7400.
The capacitor C1 of 1000 microfarads and the resistance value R1 of 150 ohms determine the rate of "movement" of LEDs.
To reduce the speed, just solder in parallel to C1, a second capacitor from 220 microfarads, for the increase, it must of course reduce this value by passing it for example to 470 microfarads.
To explain how this assembly, it should be noted that the integrated circuit IC3, a 74193, is a down counter, used to control the decimal decoder IC4, a 7442.
When the clock signal between the foot 4 of IC3, this tour validated for counting, the LEDs light up in sequence from DL1 to DL10. By cons, if the signal between the leg 5, the circuit validated for counting, the LEDs light up in sequence in DL1 DL10.
Assuming that the pendulum is activated by turning on the LED DL1 to DL10, when the last LED lights on the leg 5 of the flip-flop by IC2 IC2-A and-B, we have a pulse at logic 0 , which switches the logic levels at their outputs.
In this way, the clock frequency applied to the legs 10 and 12 of NAND gates IC2 and IC2-C-D, instead of going out the door IC2-C, out the door IC2-D.
So when this frequency between the tab 5, IC3, we get a countdown, and it is the LED DL1 DL10 at that light.
At the moment when the LED lights DL1, on leg 1 of the flip-flop consisting of two NAND gates IC2 IC2-A and-B, reaches a logic level 0, which is again switched on their output levels respectively.
In this way, the clock frequency applied to the legs 12 and 10 of NAND gates IC2 and IC2-C-D, instead of going out the door IC2-D out the door IC2-C.
So when this frequency between the tab 4 of IC3, we get a count, and it is the DL1 to DL10 LED that light up.
We bet that you will be informed of these explanations on the functioning of this clock. Simply add, that this assembly must be powered by a stabilized voltage of 5 volts (TTL requires).

Component List
R1 = 150 Ω
R2 = 220 Ω
C1 = 1000 uF electrolytic
C2 = 100 nF polyester
C3 = 47 uF electrolytic
DL1-DL10 LED = Light Emitting Diodes
Integrated IC1 = 7404
Integrated IC2 = 7400
Integrated IC3 = 74193
IC4 = Built 7442
S1 = Switch