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LED Emergency Light Circuit

This is small project for making a LED Emergency Light Circuit.

It help when power goes OFF which is very easy to build and does not cost much.

We use these LED because it saves power and last for long time.

Circuit Working:

Parts List:

CategoryItemQuantity
Resistors1k 1/4 W CFR1
100Ω 1/4 W CFR1
330k 1/4 W CFR1
CapacitorsPPC 0.47µF 400V1
Electrolytic 1000µF 16V1
SemiconductorsTransistor 2N29071
Diode 1N40073
Zener Diode 6V 1 Watt1
LEDs White Straw Hat 30mA5
Li-ion Battery 3.7V 2600mAh1

The transformer, diode and capacitor work together to give normal power.

One PNP transistor is used like a switch is main part of this circuit.

PNP device gives ground by acting like positive wire.

When base of PNP transistor get positive from power it stay OFF.

So when power is ON transistor is OFF.

When Power is ON:

If power is there transistor base get positive so transistor is OFF.

Because of this LED does not get battery power and so LED stays OFF.

Battery charge slowly from the power.

When Power is OFF:

When there is no power then transistor base does not get positive.

It get ground through 1k resistor so transistor turns ON fast.

Now battery gives power to LED and LED turn ON.

If LED light goes dim then voltage circuit diode start working slowly.

Transformerless Emergency Light Circuit:

This circuit look same like old one but there is no transformer inside so it works better.

Main Good Things:

No transformer so circuit is very small.

Less parts so it cost less money.

Easy to make because of simple design.

Be Careful and Safety First:

This circuit connect direct to AC power which is dangerous.

So person who make it must be careful and follow safety steps.

How Circuit Work:

When AC power is ON PNP transistor T1 stay OFF so it is safe.

C1, R1, Z1, D1 and C2 make small power without transformer.

When AC power goes OFF then transistor turn ON and light come.to a biased state allowing the LEDs to be lit by the battery.

Formulas:

Some Easy Formulas for Electronics.

These are basic formulas and they help when making electronic circuits.

Ohms Law:

It show how voltage (V), current (I) and resistance (R) work together:

V = I × R

Power in Circuit:

To find power (P) use:

P = V × I

Also can use these formulas:

P = I² × R

P = V² / R

Resistor Color Code:

To know resistor value with color bands use this formula:

R = (10 × first color number + second color number) Ω

3rd color is the multiply number

4th color is the tolerance how much value we can change

Capacitance (C):

Capacitor value is:

C = Q / V

Time Constant in RC Circuit:

To know time constant (τ) then use this formula:

τ = R × C

LED Resistor:

To stop too much current in LED use:

RLED = (Vsource − VLED) / ILED

Zener Diode Resistor:

To limit current for Zener diode use:

RZ = (Vsource − VZ) / IZ

Power in Transformerless Supply:

Psupply = V²rms / R

Note:

These formulas can help to make circuits but always check units and values are right.

Better to check 2 times before use.

How to Build:

Building the LED Emergency Light Circuit follow the below mentioned steps:

Build the Circuit:

Final Checks:

Power On Test:

Be Safe:

Conclusion:

This LED Emergency Light Circuit with no transformer need careful work.

Soldering must be done nicely and should put all parts in right place.

Safety is very important.

If anyone gets into problem or do not understand something then ask someone who know electronics.

Always keep safety first when making this circuit.

References:

Emergency light

Design and development of smart emergency light

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