Wiring Material: alarm

Showing posts with label alarm. Show all posts

Saturday, November 8, 2014

Build a Radio Wave Alarm

This simple circuit is sure to have the police beating a path to your door- however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat.Simple Radio Wave Alarm Circuit Diagram :

Notes :

The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or a foot approaches the sensor, the frequency of the transmitter (IC1a) drops appreciably.
Suppose now that the circuit transmits at 1MHz. Suppose also that your radio is tuned to a frequency just below this. The 1MHz transmission will therefore not be heard by the radio. But bring a hand or a foot near to the sensor, and the transmitters frequency will drop, and a beep will be heard from the radio.
Attach the antenna to a multiplug adapter that is plugged into the mains, and you will find that the Medium Wave transmission radiates from every wire in your house. Now place a suitably tuned Medium Wave radio near some wires or a plug point in your house, and an early-warning system is set up.
Instead of using the sheet of tin foil as the sensor, you could use a doorknob, or burglar bars. Or you could use a pushbutton and series resistor (wired in series with the 33K resistor - the pushbutton would short it out) to decrease the frequency of IC1a, so activating the system by means of a pushbutton switch. In this case, the radio would be tuned to a frequency just below that of the transmitter.

Thursday, October 16, 2014

Motorcycle Alarm With Transistor Circuit Diagram

This is a simple Motorcycle Alarm With Transistor Circuit Diagram. 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.

Motorcycle Alarm With Transistor 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 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. 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

Wednesday, October 15, 2014

Burglar Alarm With Timed Shutoff Circuit Diagram

When SI (sensor) is closed, power is applied to U2, a dual timer. After a time determined by C2, CI is energized after a predetermined time determined by the value of C5, pin 9 of U2 becomes low, switching off the transistor in the optoisolater, cutting anode current of SCR1 and de-energizing Kl. The system is now reset. Notice that (i6x C2) is less than (R7xC$). The ON time is approximately given by:(R7xC5)-(R6xC2) = Ton

Burglar Alarm With Timed Shutoff Circuit Diagram

Wednesday, October 8, 2014

Low Cost Fire Alarm Circuit and explanation Using Transistor

Transistor BC177 (Q1) is used as the fire sensor here. When the temperature increases the leakage current of this transistor also increases.The circuit is designed so that when there is an increase in the leakage current of Q1, transistor Q2 will get biased. As a result when there is a fire breakout the transistor Q2 will be on. The emitter of Q2 (BC 108)is connected to the base of Q3(AC 128). So when Q2 is ON Q3 will be also ON. The transistor Q3 drives the relay which is used to drive the load ie,light,bell,horn etc as an indication of the fire. The diode D1 is used as a free wheeling diode to protect it from back EMF generated when relay is switched.

Notes:

The Preset R1 can be used to desired temperature level for setting the alarm ON.
This is not a latching alarm,ie; when the temperature in the vicinity of the sensor decreases below the set point the alarm stops.
The circuit can be powered using a 9V battery or a 9V battery eliminator.
All capacitors are electrolytic and must be rated at least 10V.
The load can be connected through the C,NC,NC points of the relay according to your need.
The calibration can be done using a soldering iron,and a thermo meter. Switch ON the power supply.Keep the tip of soldering iron near to the Q1.Same time also keep the thermometer close to it.When the temperature reaches your desired value adjust R1 so that relay gets ON.

Thursday, September 11, 2014

Alarm Control Keypad Wiring diagram Schematic

The IC is a quad 2 input “AND” gate, a CMOS 4081. These gatesonly produce a HIGH output, when BOTH the inputs are HIGH. Whenthe key wired to `E` is pressed, current through R1 and D1switches Q5 on. The relay energises; and Q5 is `latched on` byR8. Thus, the Alarm is set by pressing a single key, say one ofthe tw1o non-numeric symbols.The alarm will switch off when the 4 keys connected to“A,B,C,D” are pushed in the right order. The schema worksbecause each gate `Stands` upon its predecessor.If any key otherthan the correct key is pushed, then gate 1 is knocked out of thestack, and the code entry fails.

Pin 1 is held high by R4. This`Enables` gate 1; and when button `A` is pressed, theoutput at pin 3 will go high. This output does tw1o jobs.It locksitself `ON` through R2 and it `Enables` gate 2, by taking pin 5,high. Now, if `B` is pressed, the output of gate 2, at pin 4will go high. This output does tw1o jobs. It locks itself `ON`through R3 and it `Enables` gate 3 by taking pin 12 high.Now, if `C` is pressed, the output of gate 3 will lock itself`ON` through R5 and, by taking pin 8 high, `Enable` gate 4.Pressing `D` causes gate 4 to do the same thing; only this timeits output, at pin 10, turns Q4 `ON`.

This takes the base of Q5to ground, switching it off and letting the relay drop out. Thisswitches the alarm off.Any keys not connected to `A B C D E` are wired to the base ofQ1. Whenever `E` or one of these other keys is pressed, pin 1 istaken low and the schema is reset. In addition, if `C` or `D`is pressed out of sequence, then Q2 or Q3 will take pin 1 low andthe schema will reset. Thus nothing happens until `A` ispressed. Then if any key other than `B` is pressed, the schemawill reset.Similarly, after `B`, if any key other than `C` is pressed,the schema will reset. The same reasoning also applies to `D`.The Keypad needs to be the kind with a common terminal and aseparate connection to each key. On a 12 key pad, look for 13terminals. The matrix type with 7 terminals will NOT do.

Wire thecommon to R1 and your chosen code to `A B C D`. Wire `E` to thekey you want to use to switch the alarm on. All the rest go tothe base of Q1.The diagram should give you a rough guide to the layout of thecomponents, if you are using a strip board. The code you choosecan include the non-numeric symbols. In fact, you do not have touse a numeric keypad at all, or you could make your own keypad.I haven`t calculated the number of combinations of codesavailable, but it should be in excess of 10 000 with a 12 keypad; and, after all, any potential intruder will be ignorant ofthe schema`s limitations. Of Course, if you must have a moresecure code, I can think of no reason why you shouldn`t addanother 4081 and continue the process of enabling subsequentgates. Or you could simply use a bigger keypad with more “WRONG”keys.Any small audio transistors should do.

The 27k resistors couldbe replaced with values up to 100k. And the only requirementsfor the 4k7 resistors is that they protect the junctions whileproviding enough current to turn the transistors fully on.Capacitors (C1 C2 C3 C4 C5) are there to slow response timeand overcome any contact bounce. They are probably unnecessary.

Alarm Control Keypad Circuit Diagram

Saturday, September 6, 2014

Shock alarm circuit

Here is a simple shock sensitive alarm schema that has many many applications fro home to automobiles.The main application of this schema is to use it as an anti theft alarm in automobiles.A peizo electric sensor is used as the shock sensor which has to mounted on the door which you have to protect.

Here the IC1 LM 3558 is wired as an inverting Schmitt Trigger.The POT R1 sets the threshold voltage of the schema.R1 is used as a feed back resistor.When not activated the out put from the piezo sensor will be low and so do the output of the IC.When the piezo sensor is activated its output voltage goes high and triggers the Schmitt trigger.This results the beeping of the buzzer.The buzzer remains beeping for some time even if the vibration is removed.this is because the increase in the inverting input has little effect when the IC is triggered and the state can’t be easily reversed.

Notes.

* A 3 v battery can be used as power supply.
* Fix the sensor firmly to the surface,where ever you place it.
* It is always good to place the sensor near to the door knob.
* Adjust R2 to obtain the required sensitivity.
* Assemble the schema on a good quality PCB or common board.
* Use a IC holder for mounting the IC.

Tuesday, August 26, 2014

Rain and Water Alarm Wiring diagram Schematic

This is the schema diagram of Rain and Water Alarm schema. This schema generates alarm sound when its sensor is witted by water which make a short schema (connection) between X and Y. A tone of about 1kHz which can be hear while detecting water, is provided by a stable multivariate from timer IC 555.

The sensor when witted by water completes the schema and causes the 555 oscillate at about 1kHz. It has to placed generating an angle of about 30 – 45 degrees to the ground. This tends to make the rain water to flow over it towards the ground and prevents the alarm from going on because of the stored water on top of the sensor.

The metal implemented for making the sensor is required to be aluminum and not copper. This is simply because copper forms a blue oxide on its layer on prolonged exposure to moisture and needs to be cleaned on a regular basis.The aluminum foils may be secured to the wooden / plastic board via epoxy adhesive or small screws. The connection between X and Y from the sensor may be obtained by small crocodile clips or you could possibly use screws.

Rain and Water Alarm Circuit Diagram