Long-term shutdown of the radio will easily lead to a shortened battery life, and the life of the radio will also have an impact. This article will show you how to make a radio timer switch that is easy to carry and easy to carry.
When using the radio, I often forget to turn off the phone for a long time, which not only shortens the battery life, but also has a certain impact on the life of the radio. If a timer switch is added, these problems will be solved. Now I introduce you to the touch-sensitive timer, which is not only small (can be loaded into the radio), but also very convenient to use.
Because the circuit requirements are not high, the touch-sensitive electronic switch uses only one TTL NAND gate. The TTL and NAND gate consumes very little power, so long-term connection in the circuit will not affect the battery life.
When the radio is required to work, as long as the finger touches the finger pad attached to the casing, the capacitor C1 is discharged through R2, so that the NAND input terminal is at a low potential, the output terminal is at a high potential, and the BG1 is turned on and saturated. The battery supplies power to the radio via the BG1. Since the voltage drop of the triode is only 0.1 volt when BG1 is saturated, the radio almost gets the full battery voltage.
When the finger leaves the finger touch panel, the power supply current is charged to C1 through the high resistance resistor R1. Since the time constant of the resistor R1 and the capacitor C1 is large, the voltage of the Cl rises very slowly, once the C1 voltage rises to the NAND gate. At the flat (approx. 2.4 volts), the NAND gate output is flipped low, BG1 is turned off, and the radio is turned off.
The timing control of the radio boot time is determined by R1 and C2. However, in actual operation, it can be controlled according to the length of the finger touch time, because the finger touch time is long, the residual voltage after C1 discharge is low, and vice versa. The C1 residual voltage is controlled by the length of the touch to meet the timing control requirements of the timer. The timer is tested according to the test. If the touch is 1 second, the power is turned on for about 5 minutes, the touch is 5 seconds, and the boot time is up to 35 minutes. This circuit It has few components and can be loaded inside the radio. The finger touch panel is cut with a φlOmm thin copper sheet and glued to the side of the radio with strong glue, and then introduced with a wire.
In the process of using, if you need more time than the machine, you can increase the capacity of C1, but it is better not to exceed 470uF. When this value is exceeded, the capacitance will be large, and the pocket radio will not be easy to put. In. In addition, as the capacity of the capacitor increases, its leakage current increases accordingly, making the accuracy of the timer poor.
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