siren alarm circuit diagram usng lm358

siren alarm circuit diagram

 Using this circuit diagram you can make a very powerful siren alarm powered by just a 9V battery.

This siren alarm circuit may provide the final building block in an alarm circuit using a relay to activate it.
This siren circuit is very simple and is constructed using common electronic components .
When the switch is pressed C3 charges up through R4 with a time constant of 0.47 seconds and when the switch is released C3 begins a slower discharge through R7 and R3 with a time constant of about 5 seconds. The op amp 358 used in this project is set up as a voltage controlled oscillator.

When the output of the oscillator (pin 7) switches low there is a charge remaining in C1 which holds pin 5 below the switching point. Current through R7 is proportional to the control voltage on C3. This current discharges C1 causing the voltage on pin 5 to rise towards the switching point at a rate proportional to the voltage on C3. When the switching point is reached pin 7 switches high and initially pulls pin 6 high via C1. This causes the op amp to temporarily turn on hard. But C3 quickly recharges through D2 causing the voltage on pin 5 to fall below the switching point and causing the op amp to switch off again.
The positive pulse output from the op amp puts a fixed amount of charge into C2 slightly raising the potential of pin 6. This causes the potential on pin 6 to rise and assist the sharp switch off of the op amp. Also R5 & C2 delay the rise on pin 6 long enough to get a good output pulse.

 For this siren ( alarm ) circuit you need a 9 volts battery ( or a power supply ) and a 8 ohms speaker .

5 Zone Alarm System

Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk Description
This is a complete alarm system with 5 independent zones suitable for a small office or home environment. It uses just 3 CMOS IC's and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a "system armed" indicator. The schematic is as follows:
Circuit Notes:
Each zone uses a normally closed contact. These can be micro switches or standard alarm contacts (usually reed switches). Suitable switches can be bought from alarm shops and concealed in door frames, or window ledges.

Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch. For good security this should be the metal type with a key.
Operation:
At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1. To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Source:www.zen22142.zen.co.uk

Fridge door Alarm

Beeps if you leave open the door over 20 seconds 3V battery operation, simple circuitry

Circuit diagram:

Parts:

R1____________10K   1/4W Resistor
R2___________Photo resistor (any type)
R3,R4________100K   1/4W Resistors

C1____________10nF  63V Polyester Capacitor
C2___________100µF  25V Electrolytic Capacitor

D1,D2_______1N4148  75V 150mA Diodes

IC1___________4060  14 stage ripple counter and oscillator IC

Q1___________BC337  45V 800mA NPN Transistor

BZ1__________Piezo sounder (incorporating 3KHz oscillator)

SW1__________Miniature SPST slide Switch
website:http://english.cxem.net

B1___________3V Battery (2 AA 1.5V Cells in series)

Circuit operation:

This circuit, enclosed in a small box, is placed in the fridge near the lamp (if any) or the opening. With the door closed the interior of the fridge is in the dark, the photo resistor R2 has a high resistance (>200K) thus clamping IC1 by holding pin 12 high. When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance (<2k),>

Notes:

• Connecting D1 to pin 2 of IC1 halves the delay time.
  
  
  Delay time can be varied changing C1 and/or R3 values.

  
  

  Any photo resistor type should work well.

  
  

  Current drawing is insignificant, so SW1 can be eliminated.

  
  

  Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture.

  
  

  Don't place it in the freezer.
  

  
  
  

  
  
  

  
  
  

  
  
  
  
  
  

Light Sensitive alarm

The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light. - The light-sensitivity of the circuit can be adjusted by varying the 100k preset. - The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset. Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months) you can use a pack of 6 AA alkaline batteries.