Alarm device simulators
Many modern alarm systems have light indication of security system that warns people if the car is electronically armed. Indication is usually performed on the LED, working in intermittent mode. This calms the owner, since it can make an inexperienced intruder to bypass such a car.
On sale you can find flashing LEDs with a built-in interrupter (imported). In size and appearance, they do not differ from conventional ones, Fig. 3.21 (only the price differs significantly). For example, an LED type L-56 (firm “KINGBRIGHT”) has the following parameters:
– maximum direct voltage of 2.5 V;
– The maximum forward current is 25 mA;
– maximum reverse voltage 5 V;
– temperature range -40. +85°С.
The minimum voltage at which the breaker starts to work inside such LED is 1.5 V (without the additional resistor). When using LED with a supply voltage higher than 2.5 V it is necessary to install a current-limiting resistor of 300. 1000 Ohm.
A similar alarm device can be installed in an apartment and powered directly from the mains, Fig. A thief is unlikely to find out why the indicator blinks and hurries to leave the room before the possible arrival of the police or activation of the siren.
LED indicator with intermittent glow is easy to make your own on the basis of any conventional LED and use as a mimic of the security device. It is installed near the windshield or dashboard and can be used temporarily until the alarm system is installed, or it can work as a distraction from where the connected alarm system is installed. Either way is useful.
Operating such an indicator in intermittent mode reduces the power consumption of the circuit, which is especially important when powered from a stand-alone source.
Fig. 3.23 shows the circuit of the interrupter to control the operation of a normal LED. The whole device is made on a single CMOS chip and consists of two oscillators. The generator on the elements DD1.3-DD1.6 operates at an increased frequency, but it is not noticeable when the LED is lit because of the inertia of the vision. This mode allows to reduce the current consumption of the indicator.
The second oscillator (DD1.1-DD1.2) produces pulses with a frequency of about 1 Hz, which provides intermittent LED glow (when the level of log “1” through diode VD1 is fed to input DD1/13, the oscillator on elements DD1.3 and DD1.6 stops working).
The flashing frequency of the LED depends on the rating of the elements R2-C1, and the diode VD1 prevents wrong voltage polarity of the circuit when connecting.
The circuit shown in Fig. 3.24 performs the same task, but it allows you to control a LED with two colors of glow (dual or two single colors). The device is assembled on one CMOS chip and three transistors. The circuit also consists of two pulse generators. The first one, on the DD1.1 and DD1.4 chips, operates at a frequency of 100 Hz and modulates the current through the LEDs with the help of the VT1 transistor. Because of the inertia of the vision the glow seems to be continuous.
The second oscillator (DD1.2-DD1.3) generates pulses with a frequency of about 1 Hz and provides an alternating change of the glow color (green and red). The transistors VT1. VT3 amplify the current from the output of the chip and work in the key mode as signal repeaters.
Both schemes are not critical for the choice of types of parts used. And to reduce the size of the design you can use the appropriate microcircuits from the 564 series instead.
Auto alarm light-emitting diode
Good hello all! Today, most cars are equipped with both regular security system and a third-party system. In my case, the alarm system installed from the factory. These systems have a relatively limited functionality: immobilizer, central locking, sound alarm (from the door switches). Third-party manufacturers offer a wider range of functionality, such as auto start, feedback and more. I personally do not have a particular need for this functionality, with all its advantages. But the regular security system has no LED – beacon, which is an indicator, if I may say so, more “cool” security system of the car. In most cases, yards of hooligans scare away the presence of such a system, rather than the presence of regular, which in most cases signals about unauthorized entry into the car only by the signals from the limit switches of the doors, hood. In other words, there is an opportunity to “take out the window” and take out that “bad lay”. In more advanced security systems, for example, there are shock sensors, which triggers a sound and light alert, for example, the entire yard. Yes, according to statistics, cars that have a “beacon” are broken into less frequently than cars that do not have one.
Since I do not want to spend a lot of money on a third-party security system in the absence of the need for the latter, I decided to install a dummy LED – beacon. To help, as usual, come to our “partners” from the Celestial. They, as usual, are full of all kinds of stuff. Beacon moulages also happened to be available.
I ordered them here:
Remarkable is that they are powered by an internal source and solar panels, judging by the description. Whether it is so, “autopsy” will show.
In the meantime I decided to make such a moulage myself. It needed a soldering iron, a pair of transistors, a capacitor, some resistors, a semiconductor diode, a breadboard, and actually a simple LED, as well as a free evening.
The flash frequency is determined by the value of the resistors R1 and R2 and the capacitor C1. Resistors R1 and R2 have different effect on the process. From R1 depends more on the duration of the pause between pulses, from R2 – the duration of the pulse.
Below is a table of part ratings, to set the flash frequency and power the circuit.
I chose the necessary frequency of LED flashes by changing the capacity of C1. I used KT3102 and KT3107 transistors.
I filled up the board with hot melt adhesive and covered it with masking tape because there was no suitable enclosure at hand. The circuit works. You can install it in the car.
Here is a video of my circuit working:
I plan to power the circuit from the central locking system, so that it would be visible from the window of the house that I did not forget to put the car alarm.
That’s all, dear friends, what I wanted to share. Maybe this post will be useful for someone. The scheme I took here from this site: radiokot.ru/circuit/light/flash/01/ In fact, all this nonsense, but when the itchy hands, you can make yourself. There is nothing complicated here, especially for a person who at least a little bit can hold a soldering iron in his hands and understands the element base of radio components. Good luck on the road!
