# Tiny emergency light circuit

This is first tiny emergency light of my son. It is very small, use LED display when power outage,use transistor instead relay use AA battery charger.

How it works
As Figure 1; Tiny emergency Light circuit use a few parts include the two AA nickel-metal hydride batteries, for store enough energy to drive a small lamp.

Figure 1 The tiny emergency light circuit

It works like the general emergency light; it fixtures are used to automatically provide lighting in the event of a power outage.

1. The charger section electrical energy storage in normal conditions.
2. The controller to drive the lamps light up when is power outage.

The tiny emergency light are also special, do not uses the relay to ON-OFF the lamp. But use the transistor, it acts as the switch ON-OFF instead, may be called a solid-state emergency light was.

Working began from AC power is fed into the circuit.

To fuse F1 as a blocker than the current flow may be caused by the mistakes of the circuit.

The transformer T1 will reduce the AC voltage 220V to lower about 6 volts. The AC low voltage will be rectified by diode D1 as half rectifier form. Then DC voltage will flow to resistor R1 and D2 to the battery. The charger current of circuit will set at 55 mA

When plugged into the circuit, the LEDs are not lit. Because the base lead of transistor Q1 get Reverse Bias has higher voltage than the emitter leads. The transistor will “OFF” own conduct. But when the power outage at the base leg voltage is reduced.

He does not uses the lamp because he does not has them, but he use the red super bright LED instead.

Since resistor R2 full down pull current makes transistor “ON” have current flow from the battery. Makes LED glow up. The current from battery will do not feedback to the transformer. Because there is diode D2 block the current by connected the reverse bias between the battery and transformer.

Parts you will need
Q1___BD140__PNP transistor
C1____470uF 16V Electrolytic capacitors
R1____22 ohms 1W
R2____560 ohms
D1,D2___1N4007 Diode
T1______6V 0.5A transformer
and other

How to build
He makes this circuit on universal PCB Board as Figure 2 to Figure 4. Because it is easy circuit.

Figure 2 easy to put parts on perforated PC board

Figure 3 Soldering pins

Figure 4 cut lead of parts

But you build it on PCB you can use PCB layout as Figure 5 Actual-size of Single-sided Copper PCB layout

and Figure 6 is the components layouts

Because we do not have a 2 AA battery holder. We so soldering wires directly as Figure 7

and use electrical tape as Figure 8.

Figure 9 To short-circuit protection

Figure 10 Drilling for mounting LEDs, they use only 3 LEDs, because the low power consumption.

Figure 11 Install all parts to the versatile box. Then use hot glue stick. the LED legs with the box.

Figure 12 Look inside this machine

How to use and application
He installs this corridor. He tested the device without connecting to power. If the battery power is normal and the normal LED. The LEDs will be lit up immediately.

But when the plug and LEDs are not illuminated. The charge current can be checked from voltage across the resistor R1 is calculated by the Ohm’s law.

I (current) = E (voltage) / R (resistance)

Assuming the voltage drop across the resistor R1 (22 ohms) at 1 volts charging current values are equal:
= 1 volts / 22 ohms
= 0.045 Amperes
or equals 45mA
This circuit uses the charging current 50-60mA.

When building this project completed Try it together as video below.

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