Recently, widespread quartz clock-alarm clocks Chinese production of comparatively large volume and cheapness. If the watch is out of order, but the alarm still works, it can used in various homemade designs. For example, in the proposed the bite alarm.
Operational capabilities of such a device to fully appreciate avid fishing enthusiasts (especially night). Sure: response electronics equally reliable as the sharp bite and careful how to potico inside of the reservoir, and the movement toward the coast, and the signal is supplied and light, and sound.
The basis of operation of the indicator - the interaction of magnetically operated contacts (reed switch) with a permanent magnet While the magnet close to the reed switch, the contacts are in the same condition as when you remove the magnet in the other.
Fig. 1. A circuit diagram (a) of the bite indicator, made on the basis of the electronic clock-alarm clock Chinese production and the symbol of the findings on its Board (b)
When the contacts of the reed switch open SF1 (and this is the situation when you carry this device), the transistors VT1, VT2 are closed (Fig. 1). Hence, the energy consumption is will be minimal. Indeed, when using the detector in tandem with staffing of 1.5 volt galvanic element of the supply current does not exceed 1 µa.
In standby mode, when the location of the magnet is almost over contacts of the reed switch, they are closed but the switch state is not changed.
However, it should be a magnet for at least short-term move relative to the axis of the reed switch forward or backward, as the contacts of the reed switch immediately disconnects. At the base of the first transistor through a chain R1С1 will go negative pulse. VT1 opens, and through him the charge of the capacitor C2. However, this, in turn, will unlock the second transistor and turn on the sound generator alarm clock. The capacitor C2 will begin be discharged through the resistor R3 and the emitter junction of transistor VT2.
The duration of operation of the generator depends on the parameters of the chain and С2RЗ indicated on the diagram the values of approximately 2 s. during this time and will beep.
AC voltage output 3 alarm clock is fed through capacitor C3 to led НL1 - and it flashes. The brightness depends on the value C3. Unfortunately, it is small, because if the capacity of the capacitor volume alarm sound will decrease.
The reed switch may be CAM-1, CAM-2 or similar, with contacts, working on circuit. Transistors - any number of widely distributed low-power semiconductor devices (if only the type and polarity of observed). In the quality of the capacitors is the best fit km-6 and bolsheselsky K50-35 (C3 in Fig. 2). Resistors - MLT-0,125 or MLT-0,25. The diode of any of silicon; led from the AL307.
Fig. 2. Schematic of the amplification stage to increase the brightness of the light the bite indicator
The magnet can be borrowed from the sensor burglar alarm system "QMS" plastic housing with holes for attachment of the fishing line. You can use and more accessible: for example, from furniture latches. To the permanent magnet epoxy glue EAF attach two rings at this distance, so that after dressing on the line he could not turn around its axis.
Mounted electrical schematic diagram of the device is placed in the housing type plastic boxes (Fig. 3). The led is fixed on the lid with glue or 88H epoxy. Opposite the emitter of the alarm clock in the side wall of the cover drill hole, and on top of the lid, draw a rectangle over the reed - he will precisely target the permanent magnet.
While fishing a fishing rod, the device and the permanent magnet arranged so as shown in figure 3.
Fig. 3. Rod, equipped with electronic bite alarm: 1 - shore 2 - the bite indicator; 3 - rod; 4 - the magnet on the fishing line; 5 - the pond
Author: V. Polovinkin