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 NXP Semiconductors

  • Battery-Low Beeper

  • Created: Oct 27, 2014

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This device is a simple alarm system that reliably beeps when the battery voltage falls to 10 volts. It is a portable device that can be carried anywhere to monitor a battery powered equipments with ease. The device uses 74HCT4060BQ IC, a 14-stage ripple carry binary counter with ten buffered outputs and an overriding asynchronous master reset (MR). The oscillator configuration allows design of either RC or crystal oscillator circuits.

When the voltage is above 10 volts, the zener diode conducts and turns ON the first transistor. The voltage between the collector and emitter of this transistor is less than 0.3v and the voltage on the base of the second transistor is 0.3v. Thus, the second transistor is not turned ON and it is effectively removed from the circuit. This means the reset pin of the CD 4060 is connected to the positive rail via a 1M resistor. This puts a HIGH on the reset pin and turns the chip off and prevents the oscillator producing clock pulses. The chip contains inverters between pins 9, 10 and 11 and when components are connected to these pins, an oscillator is produced. When the battery voltage falls below 10 volts, the first transistor is turned OFF and the second transistor is turned ON. This takes the reset line to the 0v rail and the chip allows the clock pulses from the oscillator to pass to a set of flip flops arranged to divide the signal. Pin 7 (Q4) divides the signal by 16 to produce a beep sound from the electro-mechanical buzzer. The buzzer normally produces a constant tone but output pin 7 goes HIGH/LOW at about one cycle per second and this turns the buzzer ON and OFF to produce a clearer alert signal. The circuit takes 30uA when "sitting around" and less than 1mA when producing a beep.

The battery low beeper is well applicable to devices that needs battery monitoring especially the batteries used by RC plane enthusiasts to avoid plane crash. This can also be used in battery operated devices such as speakers, emergency lights, electric motorcycle and other related equipments. In addition, the circuit can be altered so that it will beep at certain voltage levels.



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