Anti-Theft Tracker Alarm Circuit for Protecting valuable

The anti-theft tracker alarm Circuit explained in this article can be used for protecting any preferred valuable item by attaching the receiver device with it while the transmitter is positioned near the user for the monitoring at a preferred distance away.

As long as the item is within the allotted safe range, the transmission from the transmitter unit keeps the alarm inside the receiver unit silent, however in an even the item it tends to get misplaced  or an attempt is made to steal the valuable item, and moved away from the range, the receiver attached with the item begins producing a very shrill ear piercing noise or tone, alerting everybody around the item ad also the user whose is quickly informed regarding the item being robbed by a potential intruder.

A transmitter radiates over certain area, which range from 3 to 30 meters, a weak coded signal meant for one or more receivers positioned inside the items to be guarded. If an deceitful individual attempts to take the secured object, from a few meters, the receiver no more gets a signal and begins to emit An strong tone signaling the displacement of the protected item from the safe range.

The system may also be used as an electronic reminder for individuals who often forget their baggage in airports!

Anti-Theft Tracker Alarm Circuit for Protecting valuable

Our assembly:

The assembly suggested in this post comes into the latter category: it has been designed specifically to locate prospective thieves merged with the crowd and capable of taking away, slowly, belongings.



Our Anti-Theft Tracker Alarm Circuit for Protecting valuable circuit is considerably less complicated and more specific: it is designed for exhibitions, festivals and all scenarios whereby it is far from possible (or simply bothersome) to set up a passage control. Additionally, whenever an object has a magnetic anti-theft tag, the crook can often take it off prior to attaining a managed exit. With this technique, on the other hand, when the thief travels away a few meters, a powerful acoustic signal denounces the effort of burglary and enables, in addition to catch hold of the thief,

The wiring diagram

Let us see now how our system functions. This is fundamentally an alarm causing the transmission loss, ie a process comprising a transmitter sending a modulated HF carrier having a specific code, linked to a Receiver which stays at rest (no alarm activating) so long as it is in receipt of this carrier signal. Once we install this receiver into the item to be safeguarded and if it is outside the transmitter’s protection area, lacking of signal, its alarm is activated and a powerful and distressing whistle (see figure 9, the characteristics of the buzzer used) sounds within the object being carried away.


This product provides a couple of indisputable positive aspects: to begin with, it can be taken to rooms of different dimensions because, by adjusting the antenna of the transmitter module, a range of around 3 to 30 meters can be acquired. Additionally, possessing a single transmitter and a receiver that contains the alarm

A single transmitter hypothetically limitless can be used for tracking many number of objects simultaneously. The device is as a result modular and scalable: in its standard configuration it includes a mini-transmitter and a small receiver, but absolutely nothing stops it from associating to it as numerous receivers as there may be items to be safeguarded from one Undesirable taking away.

We may see carefully now, one and then the other of these two units, transmitter and receiver.

The TX (transmitter)

The electrical diagram of the transmitter is offered in figure 1. You can view this is a very simple circuit: a microcontroller U1 controls a hybrid transmitter module U2 and the complete is driven by a 9F 6F22 battery With an integrated voltage regulator U3.

The PIC12F672-MF417 microcontroller is previously programmed in the manufacturing plant to generate a 4-byte code (8 bits each) in speedy sequence each second. The information is fixed and the first 3 groups offer the details itself, while fourth group presents the checksum. This code is effortlessly identified by the receiver whose microcontroller is hard-wired for this!


To be able to reduce consumption as far as possible, the U2 transmitter hybrid module (an AUREL TX433SAW) is only turned on as soon as the microcontroller transmits a data stream every second.

The command sequence is as follows: once the data to be transmitted on the line GP0 is found, the line GP2 is sent to the high logic level (5 V) in order to source U2. Quickly after the 4 bytes are delivered and therefore pins 5 and 7 of the microcontroller return to the high logic state (1) for 2 seconds. Every single emission is complemented together with the lighting of the LED LD1, highlighting the working status.

The antenna must be selected based on the range, ie the preferred level of sensitivity of the activating of the alarm: typically, it is adequate to attach a simple copper wire in the slot affiliated to pin 11 of U2. In any circumstance, do not need take a piece of wire 17 cm long (which may make up a quarter wave) since you might stretch the range of the transmitter to a 100 meters … and that genuinely can spoil the objective right !

The RX

The plan of the receiver represents FIG. 5. It really is scarcely more complicated than that of the transmitter, but nothing at all exclusive is to be documented. To stimulate the buzzer (a SONITRON SMA-24L), we have executed a fascinating method. We will first observe that the radio signal is identified up by
The antenna and transferred to the input (pin 3) of the superheterodyne radio receiver hybrid module (an AUREL RX4M30RR04) working on the frequency of 433.92 MHz and furnished with a quadrature AM demodulator, Of the pin 14. The second option is attached straight to the pin 7 (GP0) of the microcontroller U1, on which it transmits all the data that it gets.
The microcontroller of the mobile receiver Is also a PIC12F672-MF418

And is previously programmed at the manufacturing plant to execute the below capabilities: after the I / O is initialized, it cyclically changes on the hybrid receiver module by delivering the Vcc pins (10 and 15) through its pin 6. Throughout the triggering cycle, it checks the status of the line GP0 where it wants data to be. If it obtains them and identifies these as legitimate, it turns off the RX for some time somewhat under the second and then turns this on once again and waits for a fresh pulse train.

Let’s evaluate one particular situation at a time, starting with the assumption that the transmitter synchronism code is acquired correctly.

Under this affliction, absolutely nothing occurs and the receiver powers down and then activates once again following a little less than a second.

In case, alternatively, in the switch-on time period the RX4M30RR04, the microcontroller does not discover the synchronism code directed by the transmitter, it raises the alarm counter through one unit and the receiver remains alight. Following another second without having code reception, the alarm counter is amplified by another unit and so on.

Reference = SMA-24L
Sound pressure at 30 cm at 12 V = 98 dBA
Frequency = 3 kHz
Voltage = 1.5 to 15 Vdc *
Consumption = 6.7 mA
Mass = 4 g

* Since only 3 V is available, a voltage elevator

However, needless to say, the circuit switches into alarm any time the synchronism signal is just not received 3 times consecutively. This goes along to the start-up of the buzzer BUZ1, that causes it to produce a very high supersonic audio tone, preventing just by turning off the power supply. Without a doubt, possibly if the object is introduced nearer to the transmitter in order that it will get the synchronous signal again, the buzzer continues to scream. In case, after one or two reception errors, the system comes back to the transmitter protection area, the alarm counter is totally reset to zero.

It is now time to think about the peculiarity of the control circuit of the BUZ1. We have aimed towards creating just as much sound as possible with a power supply of just 3 V (two LR03 / AAA batteries, maybe rechargeable type ALCAVA, in series). For this, we implemented a high-efficiency buzzer (see Figure 9), competent at emitting a note of 98 dBA of volume at 1 meter of distance. On the other hand, to have the required performances, the component needs a supply voltage of around 16 to 20 V. So, how you can accomplish ? The answer we have implemented consists in acquiring this voltage using a very simple, nonregulated switching device: once the acoustic note is to be released, The line GP5 of the PIC generates a rectangular wave at the frequency of 50 kHz, fast switching the transistor T1; The collector of the latter routinely grounded one side of the inductor L1 (the other is attached to the positive supply). The rapid switching establishes pulses with an amplitude of about 20 V, charging via the diode D1 the electrolytic capacitor C1, at the terminals of which a DC voltage of this value is acquired. To be able to transmit the note, therefore, it is enough to polarize the base of T2: this can determine the activation of the buzzer, which oscillates at about 3 kHz as a result of the electronics which it is set up. It is often mentioned, when the circuit has moved into an alarm, it isn’t achievable to deactivate the oscillator by taking the device nearer to the transmitter.

We will now take a look at a different situation:

Described that if in the course of one or two reception intervals the microcontroller would not read the synchronism code, it triggers a software counter which often takes care, from the third successive reception fault, to switch on the acoustic signal; In case, soon after a couple of reception downfalls, the code is again received, the counter is reset. This implies that, to be able to switch on the alarm, it is crucial how the reception fails again 3 times in sequence since the earlier flaws were terminated.


List of components for the TX of this Anti-Theft Tracker Alarm Circuit for Protecting valuable
R1 = 470 Ω
R2 = 100 Ω
U1 = μcontroller
U2 = Aurel Module TX433SAW
U3 = Regulator 78L05
LD1 = red LED 5 mm
1 Support 2 x 4 pin
1 Connector for 9 V battery
1 Cup 8.5 cm of enamelled wire 10
To 12/10 for antenna

List of RX Components
R1 = 100 Ω
R2 = 4.7 kΩ
C1 = 470 μF 25 V
D1 = Diode 1N4007
L1 = Self 330 μH
U1 = μcontroller
T1 = NPN BC547
T2 = NPN BC547
U2 = Module Aurel
24L with electronics
1 Support 2 x 4 pin
4 AAA battery clips
1 Cup 8.5 cm of enamelled wire 10
To 12/10 for antenna