Small areas of private territory can be protected using an electric guard made by yourself. If someone breaks into a room or a personal plot, he will break the thinnest wire with his actions. In this case, the attacker will not hear anything, since the sound signal will not work. But the owner or security guard will be aware that there are strangers on the territory.
Externally, the sensor looks miniature and simple.
A fairly thin copper wire can be found at primary winding low power transformer. The diameter of such material is so small that it does not exceed the thickness of a human hair. As a replacement, you can use fishing line or thread, but you need to make sure that the contact breaks easily when pulled. The wire can be almost any length, so you can cover a large area.
The main advantage of this system compared to a laser sensor is that the number of false alarms is reduced. For example, on the street there is an anti-burglary device that works on the principle laser beam, will respond to vibrations of bushes and grass. The electronic watchdog will only give a signal when mechanical damage chains.
The operating circuit is made in the form of an electronic key, which is triggered when the loop is damaged. If the wire remains intact, then the negative wire goes through it from the battery to the base of the NPN transistor (KT 315). Moreover, due to the negative voltage, it is always in the closed state, and a “plus” is needed to open it. If the loop breaks, the current stops flowing, and the positive voltage from a 2 mOhm resistor (R1) opens the transistor (TZ). After this, the semiconductor (T2) is saturated with current and the voltage affects the transistor with average power (KT 815). Through special terminals, the collector-emitter directs positive voltage from the battery to the sound alarm, and it turns on. You can replace the KT 915 transistor with a model with the same pinout, for example KT 940 A.
If you install a warning siren, you can scare away the criminal. But it will be much more effective to replace the loud sound with firecrackers or other pyrotechnics. Explosions and bright lights in the sky will give an amazing effect: people will avoid the house. Experts recommend buying Polish-made mega-pirates P2000 for this purpose. The small size is combined with powerful cotton and a strong reaction of the composition. The wick igniter is made of thin tungsten wire. It is necessary to provide waterproofing so that the structural elements do not become damp. This option is optimal for a country house. A regular LED is installed as an indicator, then the alert will become silent.
The board should look like the following image:
For convenience, you can download the diagram in an archive file.
The voltage should be between 9-12 V. The chemical power source in the batteries must be protected from low temperatures using special insulation. The advantage of such a security system is a small standby current (3-4 µA), so the device will work for a very long time.
The finished electric guard can be seen in the following photographs:
The video clearly shows the manufacturing process, as well as the principle of operation of the device.
Homemade connector for LCD displays Clock on gas-discharge indicators - etching of circuit boards
The simplest watchdog device can be mounted according to the diagram shown in Fig. 261. This is again familiar to you electronic relay on transistor V1, between the base and emitter of which (terminals X1 and ) a security loop is connected. This loop, indicated in the diagram by a wavy line, is a copper wire with a diameter of mm, for example, stretched along the border of a protected object. Its resistance is small - only Ohm per linear meter. Therefore, we can assume that the base of the transistor is connected directly to the emitter. Therefore, while the loop is intact, the transistor is closed. But someone, maybe a dog, wanting to get into the protected object, cut off the train. In this case, a negative voltage appears at the base of the transistor (supplied through a resistor), the transistor opens, the electromagnetic relay is activated and its contacts K1.1, closing, turn on the alarm - an electric bell, a siren, or simply an electric lamp powered from the mains.
That, in fact, is all that can be said about the principle of operation of such a watchman. The resistance of the resistor depends on the resistance of the loop and the current transfer coefficient of the transistor used. It must be selected in such a way that the electromagnetic relay operates reliably without a connected loop.
But from a technical point of view, the most interesting is the watchdog device, the diagram of which you see in Fig. 262. The protective cable of this device consists of two thin insulated wires folded together, ending in a resistor. The other end is connected through terminals X1 and connected to the emitter circuit of transistor V1.
Rice. 261. The simplest watchdog device
Rice. 262. Complicated version of the watchdog device
This transistor, together with the watchdog loop and other related parts, form an electrical oscillation generator, similar to the local oscillator of the familiar conversion stage of a superheterodyne receiver. The oscillations generated by it with a frequency of about through a capacitor are supplied to the base of the transistor V2, amplified by it and through the capacitor are fed to a rectifier on diodes V3 and V4, connected according to the output voltage doubling circuit. The rectified voltage in negative polarity is supplied through a resistor to the base of the same transistor V2, sharply reduces the negative bias voltage and, thus, closes it.
This is the standby mode of operation of the device, in which the current it consumes from the battery does not exceed . This state of the device is maintained as long as the cable is not damaged. If one of the wires of the loop breaks, the power supply circuit of the transistor will be broken, and the generation of this will sharply increase the negative voltage at the base of transistor V2, supplied to it through a resistor, the transistor will open, the relay will operate and its contacts K1.1 will turn on the alarm system. The same will happen when the cable wires are shorted. In this case, the emitter of transistor V1 will be connected directly to the common (positive) conductor of the power circuit, its operating mode will be disrupted, as a result of which generation will fail and contacts K1.1 of the relay will turn on the alarm.
In such a watchdog device, transistors with a coefficient of at least 50 must be used, and the transistor can be replaced with any other medium-power transistor p-n-p structures, For example . An electromagnetic relay with a winding with a resistance of 200-250 Ohms, for example (passport) or something similar, triggered at a voltage of no more than 9 V. The choke is homemade. It consists of 650-700 turns of wire wound on a frame with a diameter of 10-12 mm between the cheeks, glued to the frame at a distance of 20 mm from one another.
The watchman, in my opinion, will be useful for monitoring intrusions into a small area of private territory. In this case, it is necessary to have a security guard, for whom such a scheme will actually be useful. If someone or something climbs into the territory/room protected by such a thing and at the same time breaks the thinnest wire, then we will know about it and it will not necessarily be loud so as not to frighten off the intruder.
Sensor
A thin copper wire is easily located on the primary winding of any low-power transformer. It is so thin that it is even smaller than a human hair and it couldn’t be easier to break. It is also possible to use fishing line/thread, then you need to do something like this in the picture, so that when pulled, the contact breaks. This may be more effective in that it will be easier to pull on a thicker thread without breaking it. The length can be almost any, which is very pleasing in terms of covering large areas.
Sometimes a wire will be even better than a laser sensor - this is true on the streets in all sorts of bushes, grasses, and general thickets, where the beam will be pale and there will be many false positives from plants swaying in the wind.
Work diagram
The circuit is an electronic key; it is triggered when the security loop is broken. If the sensor wire is intact, then a “minus” passes through it from the power source to the base of the NPN transistor T3 (KT315) and it is in a closed state, since a “plus” is needed to open, and a negative voltage does not allow it to open. If the loop breaks, then the negative voltage no longer flows to the base of T3, but the positive voltage, which goes through the high-resistance resistor R1 with a nominal value of 2 MOhm, opens the transistor T3 and a current begins to flow through its CE, which saturates the next semiconductor T2 and also through its CE current goes and opens the last medium power transistor KT815 - now also through its collector-emitter terminals, current flows from the plus of the battery to the sound alarm and it starts working, because the minus is already connected to it. Instead of KT915, I used the KT940A transistor, it has the same pinout, we put it on the radiator.
Signal
If we place a loud siren warning, the “criminal” who has entered private territory will immediately go nuts, get scared and run out of sight or not)) ...
There is such an idea: take not an alarm, but, for example, fireworks, firecrackers or some other pyrotechnics. Just imagine the effect of a powerful explosion or bright lights in the sky. I recommend taking the Polish mega-pirates P2000; despite their small size, they have incredible power and a loud bang. We make the wick igniter from thin nichrome/tungsten wire. Do not forget that chemical elements and the wick itself can become damp - this must be taken into account.
I think it’s effective to install such a thing without a security guard at a dacha where you don’t visit often, but don’t want to see unwanted dirty guests.
You can also use an LED as an indicator, then the indication will be silent, this also has its drawbacks.
Board File
(downloads: 251)
Nutrition
The recommended voltage for power supply is 9-12 V, but it works adequately with lower values. Since the security board and batteries/accumulators will most likely be located outside, it is necessary to take care of insulating the chemical voltage source; Lithium-Ion/Polymer (Li-Ion/Po) batteries are especially afraid of the cold.
The big advantage of this system is the very low standby current, which is only 3-4 µA, this is so low that a normal power supply will work for a very long period.
Finished device (photo, video)
Electronic guard for a motorcycle
In the amateur radio literature there are many descriptions of security alarm devices for cars. However, most of these devices cannot be used to protect another popular means of transportation - a motorcycle. The author of the article published below developed his design specifically for the “two-wheeled friend” and believes that it fully meets the goal.
A version of this electronic “watchman” was published earlier in another publication. Our publication is distinguished not only by the fact that defects and shortcomings have been eliminated in the original device and its description, but also by more detailed information about making a “watchman” and setting it up. Moreover, given the relevance of the design, the editors of the Radio magazine consulted with experts on this issue. Their recommendations that increase the reliability of the device are given at the end of the article.
During the period of collecting forest gifts of nature, motorcycles standing alone along roads and clearings become easy prey for intruders. True, motorcycles are rarely stolen, but they are dismantled and fuel is stolen while the owners are picking berries or mushrooms, quite often.
The proposed guard reacts even to a slight blow to the body of the motorcycle and immediately sounds an alarm. Moreover, the signal is musical and, naturally, differs from traditional alarm signals. The owner easily recognizes him among others.
When developing a security device, we had to immediately abandon the use sound signal installed on the motorcycle because it draws too much current from the battery. The described watchman in standby mode consumes no more than 1.5 mA, and in alarm mode - up to 400 mA.
The device uses a sensor similar to that described in [ 1 ]. It is based on the ZP-22 piezo emitter, installed on the board without modification. The sensor can be placed anywhere on the motorcycle; this does not significantly affect the performance of the guard..
Electric circuit diagram security device is shown in Fig. 1. When a motorcycle body is hit, an alternating current signal appears in sensor BQ1, which is fed to the input of the comparator assembled at op-amp DA1. The comparator response threshold is set by trimming resistor R2. The top position of the resistor R2 slider in the diagram corresponds to the minimum sensitivity of the device.
If the amplitude of the negative half-waves of the sensor signal is less than the voltage across resistor R2, transistor VT1, operating in switching mode, remains closed, and the output voltage at its collector has a low level. As soon as the amplitude of the half-waves exceeds the voltage across resistor R2, the output voltage of transistor VT1 will be a sequence of rectangular pulses. Diode VD1 increases the dead band of transistor VT1.
Operational amplifier DA1 operates in maximum gain mode. The current consumed by the op amp depends on the current flowing through pin 8; resistor R5 normalizes this current. If it is in the range of 1.5...15 µA, then the current consumed by op-amp DA1 is 36...170 µA. The resistance of resistor R5 (in megaohms) is calculated using the formula [ 2 ]: R5 = (U supply -0.7V)/I 8, where U supply is the op-amp supply voltage, V; I 8 - current through pin 8, µA.
Rectangular pulses from the collector of transistor VT1 are supplied to the S input of trigger DD1.1, which leads to its switching to the single state. The direct output of the trigger is set high. Subsequent pulses arriving from the VT1 collector to the S trigger input no longer change its state.
Voltage high level from the output of trigger DD1.1 through resistor R9 it begins to relatively slowly charge capacitor C1. Its charging time is about 40 s. As soon as the voltage on capacitor C1, and therefore at the input R of the trigger, reaches the threshold for switching the trigger to the zero state, the trigger will switch and the direct output will set to a low level, if by this moment the transistor VT1 has closed and the input S of the trigger has stopped receiving pulses.
Op-amp DA1 and trigger DD1.1 are powered by a parametric voltage regulator VD2R10.
A high level voltage at the direct output of trigger DD1.1 opens transistor VT2, and relay K1 is activated. Through the closed contacts K1.1, K1.2, power is supplied to the signal device assembled on the DD2 music synthesizer.
In addition to the music synthesizer, it includes an audio signal amplifier DA2 and a dynamic head BA1. The DD2 music synthesizer is powered by a separate VD4R12 parametric stabilizer. The synthesizer is connected so that only one melody sounds. If you need to change the melody, then the circuit for switching it on needs to be changed, as shown in [ 3 ].
The AF signal amplifier DA2 is powered directly from the motorcycle battery. Resistor R13 prevents self-excitation of the amplifier. The OS circuit is formed by elements C5, R14, R15. When setting up, resistor R15 must be selected so as to achieve the maximum gain [ 4 ]. Dynamic head BA1 is connected to amplifier DA2 through coupling capacitor C6. Free pins 3-6, 9, 11 of the DD1 microcircuit are connected to a common wire.
All parts of the device, except for the switch SA1 and the dynamic head BA1, are mounted on printed circuit board made of foil fiberglass 1 mm thick. The board drawing is shown in Fig. 2.
Switch SA1 should be installed in a place known only to the owner of the machine. The dynamic head must be protected from intentional damage. It is advisable to impregnate the diffuser with waterproof varnish.
The board also needs to be protected from splashes and dust with a durable box, and the installation should be covered with epoxy varnish.
The vibration sensor can be made on the basis of the ZP-1 sound emitter and others. Microcircuit K140UD1208M can be replaced by K140UD12 , and the trigger K176TM2 - on K561TM2. Synthesizer UMS8 - any of this group; they differ only in the melodies recorded in them. The ZQ1 quartz resonator is suitable for any clock at the specified frequency.
Instead of the K174UN14 amplifier, it will do TDA2003 . Transistors VT1, VT2 can be any of the indicated series. Diodes VD1, VD3 - also any of the series KD521, KD522. We will replace the KS512A zener diode with KS212Zh, and KS139A with KS133A or to a stabistor KS119A , but with a change in the polarity of inclusion. Relay K1 - RES60, passport RS4.569.435-02. The 3GDV-1 dynamic head can be replaced with 2GD36, 4GD56, 6GDV-2. Push-button switch SA1 - P2K.
A device assembled flawlessly from serviceable parts usually starts working immediately. Resistor R2 adjusts its sensitivity after placement on the motorcycle. It is not recommended to set the sensitivity too high, otherwise the alarm will respond to soil vibration from passing vehicles, and even to the slight crackling sounds of a motorcycle cooling down after stopping.
Sensitivity also depends on the location of the vibration sensor - when it is attached to a frame or other metal structural elements, the sensitivity may be excessive.
To eliminate the acoustic connection between the dynamic head BA1 and the vibration sensor BQ1, as a result of which the alarm signal will be repeated continuously without external influences on the sensor, it is necessary to experimentally select the installation location of the head, the rigidity of its mounting and the sensitivity of the sensor.
The watchman's power source is a motorcycle battery. If the vehicle operates without a battery, it must be installed.
The device is switched into standby mode by closing contacts SA1. If you then try to manipulate the control levers, remove the motorcycle from the stand or move it from its place, the guard will immediately give an alarm. It will sound for about 40 seconds, during which time the melody will have time to sound in full. Then, provided that external influences have stopped, the security alarm will go into standby mode.
Literature
1. Vinogradov Yu. Vibration sensor for security device. - Radio, 1994, #12, p. 38.
2. Bulychev A. L. et al. Analog integrated circuits. - Minsk, "Belarus", 1993.
3. Vasiliev A. On microcircuits of the UMS series. - Radio, 1995, #12, p. 40.
4. Novachenko I.V. and etc. Microcircuits for household radio equipment. Directory. - M.: KUBK-a, 1995.
Radio magazine, number 11, 1998.
Scheme of a homemade security device - an electronic watchman, which can be used to protect a wide variety of objects.
Schematic diagram
The alarm signal is triggered either when the security loop is broken (thin wire), or when the input of element D1.1 is shorted to the common wire. In standby mode, the watchman consumes 30 µA.
After turning on the power, switch S2 begins to charge capacitor C2 through resistor R4. The voltage from this resistor is supplied to the input of the inverter D1.1 and to the inputs of the triggers D2.1 and D2.2. Triggers will be set to zero.
From level 1 s. Inverse output 2 of trigger D2.1 charges capacitors SZ and C4 through diodes V2 and VZ. While capacitor C2 is charging, closing the guard contacts S1 will not change the state of the device. The end of the charge of capacitor C2 corresponds to the application of level “0” to the input of element D1.1 and the R-inputs of triggers D2.1 and D2.2 and the device switching to standby mode. The holding time after switching on is about 20 s.
Now closing contacts S1 will cause level “1” to appear at the output of element D1.1. The edge of this pulse will switch trigger D2.7, since there is no longer a holding voltage at its R-input. Capacitors SZ and C4 will begin to discharge through resistors R5 and R6, respectively.
Reducing the voltage at the upper (according to the circuit) input of element D1.3 to zero will entail turning on a multivibrator assembled on two elements D1.3 and D1.4 OR-NOT with timing capacitor C5. From the output of element D1.3, pulses are supplied to the counting input of trigger D2.2.
From the output of the trigger, signals are supplied to the base of transistor V7, connected by an emitter follower. From the load resistor R10, the pulse voltage is supplied to the output stage on the transistor V8, the load of which is the source of the audio signal. The frequency of the sound signal is about 0.5 Hz.
The time from the moment the contacts S1 are closed until the alarm signals turn on (i.e., the discharge time of capacitor C2) is 8 s, the time for giving an intermittent alarm signal is about 3 minutes.
Reducing the voltage on capacitor C4 to zero will lead to the appearance of level “1” at the output of inverter D1.2, which, through diode V4, affects the R-inputs of triggers D2.1 and D2.2. The triggers will be set to zero, and capacitors C3 and C4 will be charged again. At the output of inverter D1.2 the level “0” will again be established.
Thus, after 3 minutes the device will return to standby mode. In addition to the normally open guard contacts S1, the device is equipped with a sensor that detects an open circuit. Structurally, it is made in the form of a security wire - a loop. When the loop breaks, level “1” appears at the R-input of trigger D2.1, and it is set to the single state.
After capacitor C3 is discharged, the multivibrator turns on. The device emits an intermittent alarm that will sound indefinitely with short intervals. To return the device to standby mode, it is necessary to restore the loop circuit, which will cause the discharge of capacitor C4.
Notes
The loop resistance should not exceed 10 kOhm. If it is made of copper wire with a diameter of 0.1 mm, its length can reach 3000 m.
