The proposed anti-theft device does not contain a hidden switch. In standby mode the device consumes electricity, which can be especially important when small vessels of the battery. The design is original in that inside motorcycle headlight "Java", but it can be applied in other types of motorcycles and cars. When you do this, be sure to note the polarity supply Board power.
A schematic diagram of a first embodiment of the device shown in Fig.1. Low power supply voltage (6) have caused the use of the relay switch enable the signal, as the voltage drop on the key transistor or thyristor significantly reduces the volume of the signal.
When you open contacts of the limit switches SB1 and SB2 and off the ignition polarized relay K1 is in a state where the contacts I-P open. Relay K2 and the audio signal are de-energized.
In the operation of the motorcycle was that anyone who came to the motorcycle with good or evil intent, immediately grabs the wheel and turns it in a comfortable position. This property and the basis of the work of the anti-theft in the device. The switches SB1 and SB2 are installed inside the headlight and is therefore not attract attention. SB2 is set so that when the right-most position of the steering wheel motorcycle its contacts are open.
When turning the steering wheel to the left, the contacts are closed, the capacitor C1 is included relay K1, closed contacts P-I, the relay K2, which their contacts activate the audible alarm. When the ignition is switched through a resistor R2 to the relay K1 is energized, contacts P-I relay K1 opens, and the audio signal ceases. It should be remembered that locks the ignition in such a motorcycle license and selection of a key in the field is virtually impossible. Block the switch SB1, climbed inside the headlight, but the switch SB1 is set for so it was impossible to remove the headlight (triggered when you try to remove the headlight).
But this leaves another opportunity to disarm the alarm by connecting the external battery to the terminals of the ignition coils, which are located under the fuel tank and have free access. To exclude this possibility, installed diode VD1. This diode must have a minimum forward voltage drop at a current up to 5 A. the fact that this diode has some undesirable implications: it is difficult to start the engine with a fully discharged battery the battery and hampered movement at low speed motorcycle engine “Java" night time with the included headlight due to insufficient capacity on-Board of the generator. But this is a precarious situation, and the way to treat it safely (applies only to motorcycles “Java").
Depending on the position of the left wheel, the scheme is in turned off or in standby condition. In off mode (steering left) the capacitor C1 remains charged, and when open (circuit) contacts SB2 relay K1 is not thrown. If you leave the steering wheel to the extreme right position, contacts SB2 will open, and the capacitor C1 is discharged through the resistor R1. The values of C1 and R1 are selected so that the discharge time is 20-30 C.
The owner must place the ignition not turning the wheel. It does not attract attention others some additional actions. If the driver long time moves coasting with the ignition off (by the way, this mode is very harmful for two-stroke engines due to the cessation of lubrication of piston) alarm still doesn't work, because the contacts SB2 cannot be open a long time, and the capacitor C1 does not have time to discharge.
However, the scheme was not very practical: when alarm is triggered device and prolonged absence of the owner “burns" sound (when good battery). To avoid this, the device was first supplemented by the multivibrator, and then and the time relay.
A modified scheme is shown in Fig.2. The scheme provides supply 3-4 sound signals on and off.
As a polarized relay must be used relay switches with two control windings, for example, RPS, RPS, RPS, RPS, RPS, RPS, RPS, RPS, RPS (suitable voltage). It is possible for such a regime to regulate and neutral polarized relay, but not they are all amenable to adjustment, and the adjustment requires a certain experience. When you install this relay on the bike, be sure to pay attention to the anchor is moved horizontally in the opposite case, when a strong shaking relay can spontaneously tossing.
As an interim, you can use any relay with powerful contacts and suitable voltage, but is better suited for this purpose relay type TC.
As a multivibrator can be used turns the relay motorcycle IZH by increasing the capacitance of the capacitors C3 and C4 in half.
The reaction of people to work for the alarm. First of surprise the man flinches and moves away, but then tries to do something, the number and spin the wheel. Then the alarm stops (time exposure). We must be prepared for everything that can go. But curiosity pulls back, and after some time he returns. Alarm goes off again. Long some of my friends were sure it was capacitive relay, but it's so much easier.
When you install such a device on the car and when used as sensor reversing light switch, we get the following: kicked by the wheel is silent, opened the door - he didn't. Hijacker calms down. But before switching on the ignition, towing, trying to roll away, the car thief is forced set the gearshift lever to the neutral position. Here the alarm is triggered.
For automotive options need to adjust the switching circuit, but it the radio Amateur with little experience. Moreover, as can SB1 to use the sensor of the engine hood.
As the limit switch SB2 I used mechanical “end". He works for me for 28 years! But sometimes after the winter we have several times to train. Applying the reed switch, you can avoid this inconvenience.
Note: even if you will watch, it is virtually impossible notice that you set off the alarm.
Author: V. M. Paley, Chernihiv