Clock & Timer Circuit DiagramsLCD-LED Display

Speed Chess Clock Schematic Circuit Diagram

Speed Chess Clock Functionality

In speed chess, players are allotted a mere 5-10 seconds to make their moves. Failing to do so results in losing the game, depending on the agreed conventions. The clock described here serves as an indicator of each player’s turn and highlights defaults. Additionally, it can be utilized for various other speed-based games.

Categories of Speed Chess

Speed chess encompasses different time controls, including rapid, blitz, and bullet formats. This variant of chess restricts the time players have to ponder their moves compared to the standard tournament time controls. The subdivisions within speed chess include rapid chess, blitz chess, and bullet chess, each offering progressively shorter time frames for decision-making.

Speed chess clock Schematic diagram

Game Timer Circuit Operation

Pressing S2 by player A illuminates D3, signaling it’s player B’s turn in the game. Player B returns the game to player A by pressing S1, causing D2 to light up. If a player fails to pass the turn back to their opponent within a set time determined by P1, the circuit activates a buzzer. The core of this circuit is a 556 timer, a dual version of the popular 555 timer. One half of IC1 (IC1b) serves as a bistable or flip-flop, keeping track of which switch was last pressed, as indicated by the corresponding LED.

The other half (IC1a) functions as a monostable. It remains in its triggered state (with the buzzer inactive) as long as it’s retriggered at regular intervals by the switches S1 and S2.

Retriggering the Timer

The trigger input is pulled low by S1 through T1 and by S2 through D1. Whenever IC1a is retriggered, the capacitor C5 is discharged through pin 1 (DIS) of IC1a, and the timing cycle controlled by P1 restarts. If either switch isn’t pressed within the allotted time, the voltage across C5 rises to the point where IC1a is reset. This sets its output low, activating the buzzer.

Current Consumption

Under normal operation, the circuit draws approximately 20 mA, which includes the illumination of one of the LEDs. When the buzzer is triggered, the current consumption increases to about 40 mA.


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