Transistor Based Motorcycle Alarm

This is a simple - easy to build - transistor based motorcycle alarm. Its designed to work at 12-volts. But - if you change the relay for one with a 6-volt coil - itll protect your "Classic Bike". The standby current is virtually zero - so it wont drain your battery.

Simple Transistor Based Motorcycle Alarm

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 centre-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.

About one minute after all of the switches have been opened again - the alarm will reset. How long it takes to switch off depends on the characteristics of the actual parts youve used. You can adjust the time to suit your requirements by changing the value of C1 and/or R3. The circuit is designed to use an electronic Siren drawing 300 to 400mA.

Simple Transistor Based Motorcycle Alarm Circuit Diagram

Its not usually a good idea to use the bikes own Horn because it can be easily located and disconnected. However, if you choose to use the Horn, remember that the alarm relay is too small to carry the necessary current. Connect the coil of a suitably rated relay to the Siren output - and use its contacts to sound the horn. 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 as close as possible to the power source. This is Very Important. The fuse is there to protect the wiring - not the circuit board.

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 its energized while the ignition is on. Then every time you turn the ignition off - the alarm will set itself. When its 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 anything else thats 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.

When you set the alarm - if one of the switches is closed - the siren will sound. This could cause annoyance late at night. A small modification will allow you to Monitor The State Of The Switches using LEDs. When the LEDs are all off - the switches are all open - and its safe to turn the alarm on.

Veroboard Layout

• Source
• zen22142

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Mains Supply Failure Alarm



Whenever AC primarys provide fails, this circuit indicators you by using sounding an alarm. It additionally gives a backup light that might be useful you in finding your approach to the torch or the generator key in the useless of night. The circuit is powered directly with the help of a 9V PP3/6F22 compact battery. Pressing of switch S1 gives the 9V energy supply to the circuit. A red LED (LED2), along with zener diode ZD1 (6V), is used to indicate the battery energy degree.

Resistor R9 limits the running current (and therefore the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full depth. As the battery voltage goes under 8V, the depth of LED2 lowers and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, each the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to majors-voltage detection optocoupler IC MCT2E (IC1) by means of resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.

Illumination of the LED within optocoupler IC1 activates its inner phototransistor and clock enter pin 12 of IC2 (connected to 9V by the use of N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used right here. When primarys goes off, IC2 is prompted after a brief period decided via parts C1, R4 and C3. Output pin 10 of IC2 goes excessive to forward bias relay driver transistor T1 by the use of resistor R7.

Circuit diagram:

Mains Supply Failure Alarm Circuit Diagram

Relay RL1 energises to prompt the piezo buzzer by means of its N/O contact for the time-out interval of the monostable multivibrator (approximately 17 minutes). At the same time, the N/C contact take aways the sure provide to resistor R4. The time-out interval of the monostable multivibrator will depend on R5 and C2. Simultaneously, output pin 9 of IC2 goes low and pnp transistor T2 will get forward biased to light up the white LED (LED1).

Light equipped by this back-up LED is sufficient to go looking the torch or generator key. During the mono time-out interval, the circuit will also be switched off by means of opening switch S1. The ‘on’ period of the monostable multivibrator is additionally changed by changing the worth of resistor R5 or capacitor C2. If majors doesn’t resume when the ‘on’ interval of the monostable lapses, the timer is retriggered after a brief prolong decided by way of resistor R4 and C3.

 

 

Source: EFY Mag

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