Bite signaling device from an electronic alarm clock. Scheme, description

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Bite signaling device from an electronic alarm clock. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Home, household, hobby

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Recently, Chinese-made quartz alarm clocks, which are distinguished by a relatively high ring volume and low cost, have become widespread. If the clock is out of order, but the alarm clock is still working, it can be used in various homemade designs. For example, in the proposed bite alarm.

The operational capabilities of such a device will be fully appreciated by avid fishing enthusiasts (especially at night). They will make sure that the reaction of the electronics is equally reliable both for a sharp bite and for a cautious one, both for pulling into the reservoir and for moving towards the shore, and the signal is given both light and sound.

The operation of the signaling device is based on the interaction of magnetically controlled contacts (reed switch) with a permanent magnet. While the magnet is near the reed switch, its contacts are in one state, and when the magnet is removed, they are in another state.

Rice. 1. Schematic diagram (a) of a bite signaling device made on the basis of a Chinese-made electronic alarm clock and a symbol of the conclusions on its board (b) (click to enlarge)

When the contacts of the reed switch SF1 are open (and this is the situation when carrying this device), transistors VT1, VT2 are closed (Fig. 1). This means that the energy consumption will be minimal. And indeed, when using the signaling device in tandem with a standard 1,5-volt galvanic cell, the supply current does not exceed 1 μA.

In standby mode, when the magnet is located almost above the contacts of the reed switch, they are closed, but the state of the signaling device does not change.

However, if the magnet moves forward or backward relative to the axis of the reed switch for at least a short time, the contacts of the reed switch will instantly open. A negative pulse will be sent to the base of the first transistor through the R1C1 chain. VT1 will open, and capacitor C2 will be charged through it. However, this, in turn, will open the second transistor and turn on the alarm sound generator. Capacitor C2 will start to discharge through resistor R3 and the emitter junction of transistor VT2.

The duration of the generator operation depends on the parameters of the C2R2 chain and, at the ratings indicated on the diagram, is approximately XNUMX s. During this time, an audible signal will sound.

AC voltage from pin 3 of the alarm clock is fed through capacitor C3 to LED HL1 - and it flashes. The brightness depends on the value of C3. Unfortunately, it is small, because as the capacitance of this capacitor increases, the volume of the alarm sound will decrease.

The reed switch can be KEM-1, KEM-2 or similar, with closing contacts. Transistors - any of the widely used low-power semiconductor devices (if only the type and polarity of the inclusion are observed). As capacitors, KM-6 and large-capacity K50-35 are the best suited (for C3 in Fig. 2). Resistors - MLT-0,125 or MLT-0,25. Diode - any silicon; LED - from the AL307 series.

Bite signaling device from an electronic alarm clock
Rice. 2. Circuit design of the amplifying stage to increase the brightness of the bite indicator light

The magnet can be borrowed from the SMK security alarm sensor in a plastic case with holes for attaching a fishing line. It is possible to use more affordable: for example, from furniture latches. Two rings are attached to a permanent magnet with EAF epoxy glue at such a distance that, after being put on a fishing line, it cannot rotate around its axis.

The mounted circuit diagram of the device is placed in a plastic box type case (Fig. 3). The LED is fixed on the cover with 88H glue or epoxy. Opposite the alarm emitter, holes are drilled in the side wall of the lid, and a rectangle is drawn on top of the lid above the reed switch - it will allow you to accurately orient the permanent magnet.

While fishing, the rod, signaling device and permanent magnet are placed as shown in Figure 3.

Bite signaling device from an electronic alarm clock
Rice. 3. A fishing rod equipped with an electronic bite alarm: 1 - shore; 2 - bite signaling device; 3 - fishing rod; 4 - a magnet on a fishing line; 5 - body of water

Author: V.Polovinkin

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