LCD-LED Display

Indicator for Dynamic Limiter Schematic Circuit Diagram

Purpose-Built Indicator for Dynamic Limiter Adjustment

This indicator serves a specific purpose: adjusting the dynamic limiter explained in another section of this edition and assessing whether any modification is required for the maximum level of the reference voltage (P1). To accomplish this, a 4-to-16 decoder IC, designated as type 4514, is employed to monitor the status of the four-bit up/down counter within the limiter circuit. This IC operates seamlessly with the ±8 V supply voltages utilized in the limiter. The limiter board incorporates a 6-way connector (K5) that provides access to the four counter outputs and the supply voltages. Connector K1 of the indicator circuit can be directly linked to K5 on the limiter board.

Indicator for Dynamic Limiter Schematic Circuit Diagram

Unique Indication with 4514 Output

One output of the 4514 becomes active (high) for each distinct 4-bit combination at its inputs, while the remaining outputs stay at logic Low. To safeguard the LEDs, individual current-limiting resistors are placed in series with each LED. A common cathode resistor couldn’t be employed due to the LEDs’ limited maximum reverse blocking voltage of 5 V, whereas the supply voltage used here is considerably higher at 16 V.

Fluid Representation Through 16 LEDs

Arranged in a row, the 16 LEDs offer a dynamic visual representation of the control process. A visual enhancement can be achieved by employing different colors for specific LEDs, such as red for D1 (indicating maximum gain) and green for D16 (representing minimum gain), while yellow is used for the remaining LEDs. When monitoring signals from various sources like TV sets, DVDs, or media players, these 16 LEDs allow for easy observation of the limiter’s behavior. It enables the adjustment of potentiometer P1 in the limiter circuit. The goal is to set it in a way that only D16 lights up at the peak signal level. If D16 remains lit regardless of P1’s position, indicating excessive illumination, P1’s value should be increased. Alternatively, P1 can be adjusted to allow the strongest signal source to slightly exceed the limiter’s control range.


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