Components used for construction, datasheets and circuit drawingts. 

Electronic Components

Below are the components required for you to build your own Emergency Light Socket.

0.82uf 250V 10% Met Polyester Cap

Highly reliable 0.82µF 250V 10% metallised polyester radial capacitor with self healing performance that offers both a high dielectric constant and strength with volumetric efficiency.

  • Ideal for commercial and multi-purpose applications, filtering, blocking, bypass and pulse operation
  • High moisture resistance
  • Non-inductive wound construction
  • Wide temperature range
  • Very high stability
  • Maximum size: L18mm x T10mm x H15mm

Quantity: 1


S9012 Transistor (PNP)

A medium power Silicon Planar PNP transistor in an E-Line package that is compatible with TO-92.

  • VCEO 45V
  • Continuous current 1A
  • 1W Power
  • Operating temperature -55°C to +200°C

Quantity: 1

470uf 10V Low Imp Electrolytic Capacitor

A very long life, ultra low impedance electrolytic capacitor with excellent ripple current capability.

Quantity: 1

1k 1% 0.4W Metal Film Resistor

1K 0.4W 1% ultraminiature metal film resistor in an axial leaded body.

Quantity: 1

Tactile Switch

PCB Switch B3F-1070 Extended

High quality SPST-NO PCB tactile switch from the Omron B3F series.

  • Size 6 x 6mm
  • Flat plunger with 9.5mm actuator
  • Operating force 0.98N
  • Positive click action
  • Horizontal mounting
  • Rated voltage 24V DC
  • Rated current 50mA

Quantity: 1

LED Emergency Light PCB


Layers: 2
Dimension: 20mm x 29mm
PCB Thickness: 1.6
PCB Color: Green
Copper Weight: 1

Quantity: 1

1N007 Diode

1N4007 1A silicon rectifier diodes

Axial Lead Standard Recovery Rectifier
VRRM: 1000 – VRSM: 1200 – VR(RMS): 700
Polarity: Cathode Indicated by Polarity Band

  • 1A maximum average forward current
  • 1000V repetitive peak reverse voltage
  • 0.8mm diameter leads

Quantity: 5

3A Time Delay Micro Axial Fuse

Micro miniature epoxy coated slow blow axial fuse, with a current rating of 3A.

  • Voltage rating 250V
  • Fuse size 2.4 x 7mm
  • Lead length 28mm
  • Leads are tinned plated copper for PCB mounting
  • Rating of fuse is printed on fuse body

Quantity: 1

Green LED

L-7104GD-5V 3mm 5V Green LED 20mcd

Miniature 3mm green LED, high quality range of components incorporating an inbuilt series resistor enabling the LED to be directly connected to 5V supply lines.

  • High intensity
  • Housed in diffused coloured package
  • Cathode identified by shorter lead
  • Low power consumption
  • Long life – solid state reliability
  • General purpose leads

Quantity: 1


IDC Cable Mounting Socket 2 x 4 Pins Pitch 2.54 mm

DC 2.54mm pitch cable mounting socket with 2 x 4 pins, made of thermoplastic polyester with fibre-glass reinforcement. 

  • Gold-plated
  • DIN 41651

Quantity: 1

COB Chips on board

3V 3W COB rigid LED strip

3V 3W COB rigid LED strip, L60mm*W8mm*thickness 1mm, 120-130LM/W, soldering pad(contact points) at the back of COB board, installation by glue.

Quantity: 1

BZX55C4V7 Zener Diode 0.5W DO35 4.7

Stabilizing and clipping circuits with high power rating.

  • Glass encapsulated
  • Zener voltage 4.7V
  • Tolerance 5%
  • Zener current 5mA
  • Housed in a DO-35 package
  • Double slug type construction
  • Colour band denotes cathode

Quantity: 1

270R 0.5W Carbon Film Resistor

Miniature high stability 270R 0.5W carbon film resistors suitable for industrial and consumer electronic equipment.

Quantity: 1

Short Pin Header Tin 2 x 4P

Tin plated double row pin header.

  • Product type: connector
  • Connector type: pin header
  • Length: 3.2mm (.1259 in )
  • Number of positions per row: 4
  • Number of rows: 2
  • Row-to-row spacing: 2.54mm (.1 in )
  • Contact plating: tin
  • Contact current rating (A): 5
  • Post size: .63mm (.024 in )
  • Mating post length: 5.8mm (.228 in )
  • Operating temperature range: -65 to +105°C

Quantity: 1

Flat Ribbon Cable Grey

Top quality Flat Ribbon Cable. This grey cable has a red strip marking the leading edge. The 8-core cable is supplied in grey.

  • 8-Core
  • AWG size: 24
  • Colour: Grey
  • Grid pitch: 2.5mm
  • Insulation material: PVC

Quantity: 1

British General 900 Series 13A 2-Gang SP Switched Plug Socket White

Robust, square-edged profile. Supplied with screw caps.

  • Raised Square Profile
  • Screwed Faceplate
  • Requires 25mm Back Box
  • Angled In-Line Terminals with Backed-Out Captive Screws
  • Fitted with Dual Earth Terminals
  • Terminals accept 3 x 2.5mm², 2 x 4mm² or 1 x 6mm² cables

Quantity: 1



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Circuit Drawing

Connection details and circuit

Circuit Drawing

Technical Information

How the circuit works

LED Emergency Light Circuit
LED Emergency Light Socket

A 820nF (0.82uF) 250 or 400 volt AC capacitor is dropping the 230 volt AC (Tested 242.4 VAC) to low volt AC (Tested 21.8 VAC).
The 0.82uf 250VAC 10% Met Polyester Capacitor  – X=1/{2xPIx50x0.82x(1/1,000,000)} = 38818.278 Ohms or 38.8 Kilo ohms. 230V/38.8 = 5.92mA

Bleeder resistor 270R 0.25W is used to remove the stored current from the C2 (0.82uF) 250 VAC capacitor.

BR IN4007 D1 through D4 rectifies the low AC to DC.

The capacitor 470uF 10V makes the DC ripple free (Tested 4.1 VDC).

This S9012 PNP transistor in TO-92 package is perfect for switching applications and switches power from the 3.7 volt battery to the light emitting diodes (COB – Circuit On Board).

Zener Diode is commonly used as a voltage regulator. Being a diode normally operated in the reverse bias and at the breakdown voltage, the zener diode allows the current to keep the voltage across the diode close to the zener breakdown 4.7 volts. Therefore it protects other devices against voltage pulses.

The 1K resistor is placed in the base to limit the current as too much base current can destroy the PNP transistor. A resistor is often used in series with the base of a transistor to limit base current. Without limiting base current you run the risk of damaging your transistor. Normally you will see 1K in the base, with 5V this gives you a base current of 5mA (I=V/R), which given a gain of 100 will not saturate at collector currents of 500mA. We want the transistor to be saturated, (turned on). So only a few mA are needed to turn a transistor on, hence a resistor is put in the base to limit the current.

The power socket has the function of emergency lighting as well as providing power supply to appliances, enabling the emergency lights to be powered and light up when the socket mains power supply is unexpectedly cut off.

The emergency lamp circuit charges the 3.7v battery using the 230 VAC electric line, when the 230 VAC power is removed, the Light Emitting Diodes (COB) will illuminate automatically.

Working voltage: 1A, 250V
Working temperature: -15 to 40 C
UK 3 pin socket output: 13A, 250V
Fits any standard back box (minimum depth of 35mm)

If your property is in an area that suffers from a disrupted power supply then emergency lighting is definitely something to consider.

A typical high-power LED will realise 10 years maintenance free service when used for 12 hours every day, thus saving the maintenance costs of replacing 20 new filament lamps over the 10 year life span and the environmental cost of their disposal.

Saving Energy
Eco Friendly

A power socket with emergency light, comprising of a power socket front switched or unswitched with a circuit board behind the socket front, a rechargeable battery and emergency light emitting diodes embedded into the socket front.

The internally mounted circuit board being provided with an external power from the sockets power supply input terminals, the rechargeable battery and the emergency light emitting diodes being in electric connection with the circuit board respectively; when the power line is connected to the socket, the emergency lights are in an off state, not illuminated; when the power line is disconnected from the external socket, fuse tripped or power cut, the emergency lights are in an on / lighted state.

The main advantage of installing emergency lighting is that your building will never be in darkness.

If an incident does occur it is crucial to make it as easy as possible for the occupants to make their way out quickly and safely through the designated escape routes.

PNP Transistor

Characteristics of the bipolar transistor S9012

Type – p-n-p
Collector-Emitter Voltage: -25 V
Collector-Base Voltage: -40 V
Emitter-Base Voltage: -5 V
Collector Current: -0.5 A
Collector Dissipation – 0.625 W
DC Current Gain (hfe) – 64 to 300
Transition Frequency – 150 MHz
Operating and Storage Junction Temperature Range -55 to +150 °C
Package – TO-92

Pin Configuration (Pinout)

The S9012 is manufactured in a plastic TO-92 case. When looking at the flat side with the leads pointed downward, the three leads emerging from the transistor are, from left to right, the emitter, base, and collector leads.

Classification of hFE

S9012 can have a current gain anywhere between 64 and 300. The gain of a S9012D will be in the range from 64 to 91, S9012E – range from 78 to 112, S9012F – range from 96 to 135, S9012G – range from 112 to 166, S9012H – range from 144 to 202, S9012I – range from 190 to 300.

Replacement and equivalent transistor for S9012

You can replace S9012 with 2SA708, 2SA709, BC527, BC528, KSA708, KSP55, KSP56, KSP92, KSP93, MPS3702, MPS4354, MPS6652, MPS6652G, MPSA92, MPSA93, MPSW51, MPSW51A, MPSW51AG, MPSW51G, MPSW55, MPSW55G, MPSW56, MPSW56G, MPSW92, MPSW92G, PN4354, ZTX554, ZTX555, ZTX556, ZTX557

LED Emergency Light Socket


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