circuit harness wiring

Thursday, December 19, 2013

Fire Alarm

   Here is a simple circuit which can be used as a Fire Alarm. 3 Volt is enough to operate. There is not much to the circuit. The IC UM66 is connected to its supply and its output fed to a transistor for amplification.
   UM66 is a complete miniature tone generator with a ROM of 64 notes, oscillator and a preamplifier. For amplification we have used a NPN transistor which is BC548. Here BC548 makes a common emitter circuit. For limiting the base current we have used a resistance of 220 Ohms so that transistor will not get damaged even if IC is wrong connected.
   For heat sensor we have used tube light starter in place of manual switch. In a starter there is a metal plate and a pin with small gap. When starter gets heated then metal plate of starter expands and get in contact with the pin and circuit is completed and we get audio from speaker. For fast sensing we can use starter without its glass body by carefully breaking glass cover.

Circuit Diagram of Fire Alarm

MATERIALS REQUIRED

STARTER 1

3V BATTERY 1

IC UM66 1

BC 548(TRANSISTOR) 1

220 OHMS(RESISTOR) 1

Saturday, August 3, 2013

Door Handle Alarm Circuit Using Transistor

The automatic door handle alarm circuit gives a audible alarm and glows a LED when somebody touches the handle of the door. The circuit is latching type and continues to produce sound until it is switched off.

The transistor Q1 is wired as an astable multi vibrator whose output is used to bias transistor Q2 to conduction. As a result the transistor q3 and LED are in OFF state. When someone touches the handle, the capacitance of the human body damps the oscillations of Q1.The cuts the biasing of Q2 and it goes OFF.As a result the current flows to the base of Q3 , it conducts and LED glows. If the switch S1 is ON the transistor pairs Q4&Q4 which is wired in the latching mode is triggered and the Buzzer Z1 is activated. When the person removes his hand from door handle the LED goes OFF but the buzzer continues to beep. The only way to mute the buzzer is to open the switch S2. All capacitors must be rated 15V.

A 9V battery or 9V DC power supply can be used to power the circuit. To make L1 wind 25 turns of 0.4 mm enameled copper wire on resistor R2 and solder the ends of the wire to the resistor leads. This unit will stand for the R2 as well as L1 because both are parallel in the circuit. A readily available 10mH inductor can be used for L2. Connect the point A in the circuit to the door handle using a long wire.

Sunday, May 19, 2013

Smoke Alarm Using 555

The smoke alarm circuit presented here is based on the readily available photon-coupled interrupter module and timer IC NE555. The photo interrupter module is used as the smoke detector, while timer 555 is wired in astable configuration as an AF oscillator for sounding alarm via a loudspeaker.

Circuit diagram of Smoke Alarm Using 555: Click on image to enlarge

In the absence of any smoke, the gap of photo interrupter module is clear and the light from LED falls on the phototransistor through the slot. As a result, the collector of phototransistor is pulled towards ground. This causes reset pin 4 of IC 555 to go low. Accordingly, the timer is reset and hence the alarm does not sound.

However, when smoke is present in the gap of the photo interrupter module, the light beam from LED to the phototransistor is obstructed. As a result, the phototransistor stops conducting and pin 4 (reset) of IC 555 goes high to activate the alarm.

Note: The unit must be housed inside an enclosure with holes to allow entry of smoke.

Tuesday, May 14, 2013

High Low voltage cut off with delay alarm

This straight forward circuit will protect electrical appliances from over voltage as well as under voltage.The circuit also produces an alarm when the power supply comes back.An ideal circuit for home to protect your valuable equipments from voltage fluctuations.The same circuit with some modifications can be used to make a automatic voltage stabilizer

When the mains voltage is in the normal level ,the voltage at the negative terminal of zener diode D4 will be less than 5.6 Volts.At this condition transistor T1 will not conduct.The same time voltage at the negative terminal of zener diode D5 will be greater than 5.6 and so the transistor T2 will be conducting.The relay will be activated and the green LED wil be glowing.

When the mains voltage is higher than the set limit the transistor T1 becomes conducting since the voltage at the negative terminal of D4 is greater than 5.6 V.At the same time transistor T2 will be non conducting which results in the deactivation of relay to cut the mains supply from load.When the mains voltage is less than the set limit transistors T1 & T2 becomes non conducting making the relay to de- activate and cut the load from mains.Ω

The timer NE555 is wired as a monostable multivibrator with a pulse width of 10ms.When the power comes back after a cut off a negative voltage is obtained at the trigger pin which triggers the IC NE555.The transistor T3 gets forward biased and it drives the buzzer to produce a beep as an indication of power resumption.Also the transistor T1 is made on which in turn makes T2 off.As a result the relay will remain de- activate for 10ms and this provides the sufficient delay and the equipment is protected from surge voltages.

* To calibrate the circuit a autotransformer is needed.Connect the output of autotransformer to the transformer primary.
* Set the voltage to 260V and adjust VR1 to make the relay deactivated.
* Now set the autotransformer to 160V and adjust VR2 so that the relay is de-energized.
* VR3 can be used to vary the volume of buzzer.

Saturday, April 13, 2013

5 Zone Alarm System

This is an entire alarm system with 5 impartial zones appropriate for a small place of business or home environment. It uses just 3 CMOS ICs and includes a timed entry / exit zone, 4 fast zones and a panic howeverton. There are indicators for each zone a \"system armed\" indicator. The schematic is as practices:

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Circuit Notes

Each zone makes use of a generally closed contact. These can be micro changees or usual alarm contacts (usually reed switches). Suitable switches can also be bought from alarm shops and hid in door bodys, or window ledges.

Zone 1 is a timed zone which need to be used because the entry and exit point of the constructing. Zones 2 - 5 are fast zones, for you to trigger the alarm with out a delay. Some RF immunity is presentd for lengthy wiring runs by the input capacitors, C1-C5. C7 and R14 also kind a transient suppressor. The key change acts as the Set/Unset and Reset change. For just right security this must be the metallic kind with a key.

Operation
At change on, C6 will cost by approach of R11, this acts because the exit extend and that is set to round 30 2nds. This may also be altered through varying either C6 or R11. Once the timing length has elapsed, LED6 will mild, which implys the device is armed. LED6 could additionally be installed externally (at the bell box for example) and provides visual indication that the device has set. Once set any contact that opens will set off the alarm, including Zone 1. To stop set offing the alarm on entry to the constructing, the concealed re-entry change need to be functiond. This will discharge C6 and begin the entry timer. The re-entry change can be a hid reed swap, positioned anywhere in a door frame, however invisible to the attention. The panic swap, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Author : Andy Collinson