The following block diagram shows a security/alarm device. This is a one shot device and been used by Russian military for many years. The device is designed to be very difficult to disarm. It can be used to defence the permitter and it can activate alarm , pyrotechnic noise maker and even a claymore. The left side is timing and power unit and the right side is execution unit. These two units are connected via a 50cm wire together. The sequences of events are as follows:
1. After connecting battery 1, the switch 3 is pressed, the current goes through the long, thin (40m) break wire 2 and reaches the oscillator 5. At the same time counter 6 is reset and timer is starting to work. The progress of timer is shown via logic gate7 and LED8. If the tripwire is not connected correctly, the LED won't turn on as there is no current reaching oscillator. This is a safety
feature.
2. When the timer stops after approx 7min, one input of logic gate 9 goes high. The other was already high through the tripwire. As a result, the output of logic gate goes high. This sends a current to the voltage threshold circuit, possibly using a zener diode and a NPN transistor.
3. When an intruder breaks the tripwire, the current source of the oscillator no longer exist, which means inputs of logic gate go low and so the output. The zener diode of voltage threshold detects this and activates the load.
4. The device will also activate if anyone attempt to remove the battery, tamper with execution unit (trembler switch), cut the connecting wires and also when the voltage drops to 6.5v (self-destruct).
My question is, what type of oscillator/ counter is likely to be used in this device? I am fascinated by this device and I'd like to replicate on and connect a firecracker as an alarm. I am tempting to use CD4060BE as it has built in oscillator and consumes low current but I am not sure running a 40m wire for it's power pin is a good idea. The oscillator needs to be robust against noises. Definitely a good filtering caps and ferrite beads are needed. What type of oscillator/ counter would you choose?
1. After connecting battery 1, the switch 3 is pressed, the current goes through the long, thin (40m) break wire 2 and reaches the oscillator 5. At the same time counter 6 is reset and timer is starting to work. The progress of timer is shown via logic gate7 and LED8. If the tripwire is not connected correctly, the LED won't turn on as there is no current reaching oscillator. This is a safety
feature.
2. When the timer stops after approx 7min, one input of logic gate 9 goes high. The other was already high through the tripwire. As a result, the output of logic gate goes high. This sends a current to the voltage threshold circuit, possibly using a zener diode and a NPN transistor.
3. When an intruder breaks the tripwire, the current source of the oscillator no longer exist, which means inputs of logic gate go low and so the output. The zener diode of voltage threshold detects this and activates the load.
4. The device will also activate if anyone attempt to remove the battery, tamper with execution unit (trembler switch), cut the connecting wires and also when the voltage drops to 6.5v (self-destruct).
My question is, what type of oscillator/ counter is likely to be used in this device? I am fascinated by this device and I'd like to replicate on and connect a firecracker as an alarm. I am tempting to use CD4060BE as it has built in oscillator and consumes low current but I am not sure running a 40m wire for it's power pin is a good idea. The oscillator needs to be robust against noises. Definitely a good filtering caps and ferrite beads are needed. What type of oscillator/ counter would you choose?
