Low battery indicator. Encyclopedia of radio electronics and electrical engineering
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Low current consumption in standby mode (2 mA), small dimensions of the device (board dimensions - 36x48 mm) and adjustable threshold allow the signaling device (from the NF400 set by MASTER KIT) to be used in almost any equipment, including those with battery power. The device will also find application as a signaling device for the discharge of a car battery.
Rice. 1. Appearance of the device
Rice. 2. Schematic diagram of the device
When the specified threshold of the controlled voltage is lowered, the device emits an audible signal. The signaling threshold (voltage 8.13 V) can be adjusted with a trimming resistor VR1. To power the signaling device, a DC source with a voltage of 8.15 V and a load current of at least 100 mA is suitable.
On transistors TR1 and TR2, an electronic key is made, the threshold of which can be adjusted by a trimming resistor VR1.
When the supply voltage drops below the value set by the trimmer resistor VR1, the threshold and electronic key is activated and supplies power to the multivibrator circuit (sound generator) made on transistors TR3 and TR4. From the output of the multivibrator, an audio signal is fed to a power amplifier made on a TR5 transistor, and then to a miniature piezoelectric emitter PZ.
Structurally, the device is made on a printed circuit board made of foil fiberglass with dimensions of 36x48 mm.
To configure the device, it is desirable to connect it to a power source with the ability to smoothly adjust the output voltage in the range of 8 ... 15 V.
A voltage equal to 12 ... 15 V is supplied to the signaling device from an adjustable power source. By smoothly reducing the supply voltage, the operation of the signaling device is checked (until an audible signal appears).
Set the supply voltage equal to the desired alarm threshold. Slowly rotating the tuning resistor VR1, they wait until the signaling device is triggered.
To save time and relieve you of the routine work of finding the necessary components and manufacturing printed circuit boards, MASTER KIT offers the NF400 kit. The kit consists of a factory printed circuit board, all necessary components and instructions for assembly and operation.
Author: Yuri Sadikov
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