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:
| Category | Item | Quantity |
|---|---|---|
| Resistors | 1k 1/4 W CFR | 1 |
| 100Ω 1/4 W CFR | 1 | |
| 330k 1/4 W CFR | 1 | |
| Capacitors | PPC 0.47µF 400V | 1 |
| Electrolytic 1000µF 16V | 1 | |
| Semiconductors | Transistor 2N2907 | 1 |
| Diode 1N4007 | 3 | |
| Zener Diode 6V 1 Watt | 1 | |
| LEDs White Straw Hat 30mA | 5 | |
| Li-ion Battery 3.7V 2600mAh | 1 |
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.
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
- Q is the charge
- V is the voltage
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
- Vsource is the power voltage
- VLED is the LED drop voltage
- ILED is the LED current
Zener Diode Resistor:
To limit current for Zener diode use:
RZ = (Vsource − VZ) / IZ
- VZ is the Zener voltage
- IZ is the Zener current
Power in Transformerless Supply:
Psupply = V²rms / R
- Psupply is the power
- Vrms is the AC voltage
- R is the load resistor
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:
- First be sure all parts we have used are easy to find in market.
- Before starting turn OFF all power.
- Wear safety things like gloves and safety glasses.
- Use the circuit diagram schematic to plan how we can place parts on board.
- Connect PNP transistor T1 like shown in the diagram.
- Build the transformerless power supply using C1, R1, Z1, D1 and C2.
- When we add LEDs be sure positive and negative sides polarity are correct.
- If using 6V battery then change circuit like told before.
- Put resistors R1 and R2 in right place.
- Add diodes D1, D2 and D3 after checking circuit.
- Connect rectifier diode like shown in instructions.
- When putting battery also check the + and − sides polarity are correct.
Final Checks:
- Check every wire and part are in correct place and check two times.
- Look for bad soldering and fix if needed.
Power On Test:
- Now connect power and see if circuit is working.
- Check if LEDs turn ON when main power is OFF.
Be Safe:
- Cover the circuit with plastic case or cover.
- Add insulation for safety.
- Do not touch circuit when it is connected to AC power.
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.