Enhancing Clock Radio Sound Control
Inexpensive clock radios often lack separate controls for sleep mode and wake-up volumes. However, a small and easily installable circuit can enable you to fall asleep to soft music while ensuring you wake up on time. This is accomplished without the need for fitting an additional potentiometer. Instead, the circuit slightly boosts the volume level in relation to the preset level. To achieve this, the ground connection of the volume potentiometer is disconnected and a trimpot is introduced. Adjusting this trimpot is a matter of personal preference and is influenced by the original volume potentiometer’s setting. As a general guideline, approximately one-quarter of the original potentiometer’s setting is recommended. To ensure the volume can be completely reduced to zero, a transistor is connected in parallel with P1, short-circuiting the trimpot. Both additional components should be directly soldered to the original post to enhance noise suppression.
Transistor Control Using R-S Flip-Flop
An R-S flip-flop, constructed from AND gates and delay networks, serves to regulate the transistor. This flip-flop, composed of IC1a and IC1b, is initially set with a High output from IC1a, triggered by a Low pulse stemming from the RC network R2/C2. Subsequently, the signal from IC1a, following a time delay induced by R3 and C3, reaches both inputs of IC1c. Only when both of these inputs attain a High level does IC1c cut off the transistor. The wake-up music starts at a reduced volume level due to this time delay, gradually transitioning to the predetermined level as the delay period elapses. To manually decrease the volume level, one can press the reset switch S1. Doing so lowers the input of gate IC1b, thereby causing the R-S flip-flop to shift to the opposite state. The bistable stage remains in this state until the power supply is deactivated.