Emergency Light & Alarm

Device purpose:

This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen.
When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored. 

Circuit operation:

Mains voltage is reduced to about 12V DC at C2's terminals, by means of the reactance of C1 and the diode bridge (D1-D4). Thus avoids the use of a mains transformer.
Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging.
Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair.
If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker.
If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2.
If SW1 is closed, restoration of the mains supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.

Notes:

• Close SW2 after the circuit is plugged.
• Warning! The circuit is connected to 220Vac mains, then some parts in the circuit board are subjected to lethal potential!. Avoid touching the circuit when plugged and enclose it in a plastic box.

Parts:

R1____________220K   1/4W Resistor
R2____________470R   1/2W Resistor
R3____________390R   1/4W Resistor
R4______________1K5  1/4W Resistor
R5______________1R   1/4W Resistor
R6_____________10K   1/4W Resistor
R7____________330K   1/4W Resistor
R8____________470R   1/4W Resistor
R9____________100R   1/4W Resistor

C1____________330nF  400V Polyester Capacitor
C2_____________10µF   63V Electrolytic Capacitor
C3____________100nF   63V Polyester Capacitor
C4_____________10nF   63V Polyester Capacitor

D1-D5________1N4007 1000V 1A Diodes
D6______________LED  Green (any shape)
D7___________1N4148   75V 150mA Diode

Q1,Q3,Q4______BC547   45V 100mA NPN Transistors
Q2,Q5_________BC327   45V 800mA PNP Transistors

SW1,SW2________SPST Switches
SW3____________SPDT Switch

LP1____________2.2V or 2.5V 250-300mA Torch Lamp

SPKR___________8 Ohm Loudspeaker

B1_____________2.5V Battery (two AA NI-CD rechargeable cells wired in series)

PL1____________Male Mains plug

 Enjoy.......

LED STEREO SOUND LEVEL INDICATOR

Many circuits can be designed as level indicators by using a comparator IC or transistors but these are costly and complex and also time consuming. This circuit removes all the complexity by using a single TA7666p IC. LEDs are used as a power indicator. Different colour LEDs can be used for both the channels. One can also use an LED bargraph display. INPUT signals should be given from preamplifiers. Otherwise, LEDs will not glow at low volumes.

PARTS LIST
R1-R10	1kΩ
R11	15kΩ
R12	15kΩ
C1	0.1µF
C2	0.1µF
C3	1µF 16V
C4	1µF 16V
D1-D10	10 LEDs
IC1	TA7666P

If you have mono systems, signals should be given into both the channels. The input is given through two 4.7 µF capacitors and two 18k resistors to pins 1 and 16 respectively.

• Suitable for stereo LED driver
• Wide Supply Voltage Range : V_CC = 6V to 12V
• Low Quiscent Current : I_CCQ = 4ma (typ.) at V_cc = 9V
• Variable Voltage Gain Because of Inverting Amplifier
• Easy Arrangement for Dual 10 LED’s Driver by Series Connection of TA77666P and TA7667P

Audio VU Meter

This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324.

The 1K resistors in the circuit are essential so that the LED's turn on at different audio levels. There is no reason why you can't change these resistors, although anything above 5K may cause some of the LED's to never switch on. This circuit is easily expandable with more op-amps, and is not limited to use with the LM324. Pretty much any op-amp will work as long as you look up the pinouts and make sure everything is properly connected.

The 33K resistor on the schematic is to keep the signal input to the circuit at a low level. It is unlikely you will find a 33K resistor, so the closest you can get should do. The value of this resistor may need to be changed, so it is best you breadboard this circuit before actually constructing it on PCB. The circuit in it's current form will accept line level inputs from sources such as the aux out on a Hi-Fi, all though could be easily modified to accept speaker inputs.

The audio + is connected to the main positive rail, while the audio - is used for signal input. The 50k pot can be used to vary the sensitivity of the circuit.

Battery Charger for 12V SLA

                              Battery Charger for 12v SLA(Sealed Lead-Acid)  Batteries