Showing posts with label alarm. Show all posts
Showing posts with label alarm. Show all posts
Tuesday, December 17, 2013
Build Motorcycle Alarm Circuit Diagram
This is a Motorcycle Alarm Circuit Diagram. Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its center-stand. Use micro-switches to protect removable panels and the lids of panniers etc. While at least one switch remains closed, the siren will sound.
Motorcycle Alarm Circuit Diagram
About tw1o minutes after the switches have been opened again, the alarm will reset. How long it takes to switch off depends on the characteristics of the actual components used. But, up to a point, you can adjust the time to suit your requirements by changing the value of C1.The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction.Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it. Fit a 1-amp in-line fuse close to the power source.
This protects the wiring. Instead of using a key-switch you can use a hidden switch; or you could use the normally closed contacts of a small relay. Wire the relay coil so that it is energized while the ignition is on. Then every time you turn the ignition off, the alarm will set itself.When it`s not sounding, the circuit uses virtually no current. This should make it useful in other circumstances. For example, powered by dry batteries and with the relay and siren voltages to suit, it could be fitted inside a computer or any thing else that`s in danger of being picked up and carried away. The low standby current and automatic reset means that for this sort of application an external on/off switch may not be necessary.
Wednesday, March 27, 2013
Car Alarm Sound Booster
For car alarms, emphasis should be put on hearing the audible alert and identifying it as belonging to your ‘wheels’. Unfortunately, modern car alarm systems seem to have more or less the same alarm sound especially if they are from the same brand. Also, to comply with legal noise restrictions, the alarm sound is not always loud enough to be heard if the car is parked down the road.
The circuit shown here is designed to help boost the alarm sound by also activating the car’s horn(s) when the alarm goes off.Internally the car alarm system often provides a signal that activates the (optional) engine immobilizer and/or volume (ultrasound) sensors. This signal usually goes Low upon system triggering and high again when the alarm system is deactivated.
Car Alarm Sound Booster Circuit Diagram :
The alarm activation signal is fed to the circuit through D1. When in idle state, T1’s gate is High and consequently the FET conducts, keeping power FET T2 firmly switched of f. When the system gets an active low signal, T1 switches of f allowing timing capacitor C2 to charge via R2. About 15 seconds later, when the voltage across C2 is high enough, T2 starts to conduct and relay RE1 is energized. This, in turn, provides the required path for the ‘lights flashing’ signal to energize RE2 and feed battery power to the car’s horn(s).
When the alarm system is turned off the activation signal returns to High. T1 starts to con-duct and rapidly discharges C2 via R3. T2 is then cut off and RE1 is de-energized. Diode D2 suppresses back EMF from RE1.The circuit draws less than 2 mA when idling. When activated the circuit’s current consumption is virtually that of the RE1 coil.RE1 is any simple SPST or SPDT relay, capable of switching about 0.5 A (at 12 V). The coil rating is for 12 VDC and a current requirement as low as you can find. Fuse F1 should be a slow blow type and rated about twice RE1’s coil current.
The BS170 in position T2 can sink a continuous current of about 0.5 A. However, a value of 1.2 A pulsed is specified by Fairchild for their devices. To keep the FET’s d-s current due to C2 discharging within safe limits, R2 may be increased, C2 decreased and R3 increased, all proportionally. A factor of 2 will keep the FET out of harm’s way with maybe a slight change in the 15-second delay and the sensitivity of the circuit.C1 is used as a smoothing capacitor and F2 should be rated in accordance with the horn(s) maximum current draw.
Caution.The installation and use of this circuit may be subject to legal restrictions in your country, state or area.
Source : ecircuitslab.com
Door Alarm Circuit
Hangs up on the door-handle Beeps when someone touches the door-handle from outside
This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from the outside. The alarm will sound until the circuit will be switched-off.
The entire circuit is enclosed in a small plastic or wooden box and should be hanged-up to the door-handle by means of a thick wire hook protruding from the top of the case.
A wide-range sensitivity control allows the use of the Door Alarm over a wide variety of door types, handles and locks. The device has proven reliable even when part of the lock comes in contact with the wall (bricks, stones, reinforced concrete), but does not work with all-metal doors. The LED is very useful during setup.
Circuit diagram:
Door Alarm Circuit diagram
Parts:
R1______________1M 1/4W Resistor
R2______________3K3 1 or 2W Resistor (See Notes)
R3_____________10K 1/2W Trimmer Cermet (See Notes)
R4_____________33K 1/4W Resistor
R5____________150K 1/4W Resistor
R6______________2K2 1/4W Resistor
R7_____________22K 1/4W Resistor
R8______________4K7 1/4W Resistor
C1,C2__________10nF 63V Ceramic or Polyester Capacitors
C3_____________10pF 63V Ceramic Capacitor
C4,C6_________100nF 63V Ceramic or Polyester Capacitors
C5______________2µ2 25V Electrolytic Capacitor
C7____________100µF 25V Electrolytic Capacitor
D1,D2,D4_____1N4148 75V 150mA Diodes
D3_____________5 or 3mm. Red LED
Q1,Q2,Q3,Q5___BC547 45V 100mA NPN Transistors
Q4____________BC557 45V 100mA PNP Transistor
L1_________________ (See Notes)
L2_____________10mH miniature Inductor
Hook_______________ (See Notes)
BZ1___________Piezo sounder (incorporating 3KHz oscillator)
SW1,SW2________SPST miniature Slider Switches
B1_______________9V PP3 Battery
Clip for PP3 Battery
Circuit operation:
Q1 forms a free-running oscillator: its output bursts drive Q2 into saturation, so Q3 and the LED are off. When part of a human body comes in contact with a metal handle electrically connected to the wire hook, the body capacitance damps Q1 oscillations, Q2 biasing falls off and the transistor becomes non conducting. Therefore, current can flow into Q3 base and D3 illuminates. If SW1 is closed, a self-latching circuit formed by Q4 & Q5 is triggered and the beeper BZ1 is activated.
When the human body part leaves the handle, the LED switches-off but the beeper continues to sound, due to the self-latching behavior of Q4 & Q5. To stop the beeper action, the entire circuit must be switched-off opening SW2. R3 is the sensitivity control, allowing to cope with a wide variety of door types, handles and locks.
Notes:
- L1 is formed winding 20 to 30 turns of 0.4mm. diameter enameled copper wire on R2 body and soldering the coil ends to the resistor leads. You should fill R2 body completely with coil winding: the final turns number can vary slightly, depending on different 1 or 2W resistor types actual length (mean dimensions for these components are 13 - 18mm. length and 5 - 6mm. diameter).
- The hook is made from non-insulated wire 1 - 2mm. diameter (brass is well suited). Its length can vary from about 5 to 10cm. (not critical).
- If the device is moved frequently to different doors, Trimmer R3 can be substituted by a common linear potentiometer fitted with outer knob for easy setup.
- To setup the device hang-up the hook to the door-handle (with the door closed), open SW1 and switch-on the circuit. Adjust R3 until the LED illuminates, then turn slowly backwards the screwdriver (or the knob) until the LED is completely off. At this point, touching the door-handle with your hand the LED should illuminate, going off when the hand is withdrawn. Finally, close SW1 and the beeper will sound when the door-handle will be touched again, but will not stop until SW2 is opened.
- In regular use, it is advisable to hang-up and power-on the device with SW1 open: when all is well settled, SW1 can be closed. This precautionary measure is necessary to avoid unwanted triggering of the beeper.
Source : www.redcircuits.com
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