3 Simple LED Emergency Light Circuit

This LED emergency light project is simple, cheap and easy to build. The circuit do the charging of the battery and when the main source is not available such as in brownouts, the white LEDs automatically turn on. Click schematic below to enlarge.

emergency light schematic diagram

Initially, the voltage output from 220V to 12V converter is fed to the input of LM317 regulator. Then this voltage is regulated down to 7.37V using 240 ohms and 1.2K resistor combination (see LM317 Calculator). At this instant, the battery is in charging mode and the transistor Q1 is off. Indicator LED serves two purposes, one primarily is to give us idea that the battery is charging and another is to ensure that the Q1 is off. During brownouts, the transistor Q1 is on and delivers current to 16 white LED of about 20mA each, thus a fully charged battery (6V/4.5Ah) can last up to 14 hours.
The charger has no built in over-current control but still it protects the battery from overcharging since the charging voltage is set only to 7.4V.

Part List: 6V VERSION
D1 - 1N4001 diode (3pcs)
C1 - 1000uF/25V electrolytic capacitor
R1 - 200 ohms 1/4W
R2 - 1 kilo ohms 1/4W
R3 - 1.5 kilo ohms 1/2W
R4 - 120 ohms 1/4W (16pcs)
LM317 - varaible voltage regulator
indicator LED - red or any low power LED (3mm or 5mm)
LED - white LED 3V@30mA (16pcs)
Q1 - TIP42C or similar PNP transistor
Transformer - 220V to 12V-0-12V , center tap 12VA
Battery - 6V 4.5ah lead -acid battery

Part List: 12V VERSION

D1 - 1N4001 diode (3pcs)
C1 - 1000uF/25V electrolytic capacitor
R1 - 220 ohms 1/4W
R2 - 2.2 kilo ohms 1/4W
R3 - 1.5 kilo ohms 1/2W
R4 - 390 ohms 1/4W (16pcs)
LM317 - varaible voltage regulator
indicator LED - red or any low power LED (3mm or 5mm)
LED - white LED 3V@30mA (16pcs)
Q1 - TIP42C or similar PNP transistor
Transformer - 220V to 12V-0-12V , center tap 12VA
Battery - 12V lead-acid battery

Part list diagrams: click to enlarge

TIP42C pins

LED pins

LM317 pinout

But if you want a much handy and smaller led emergency light, try building a cellphone charger-based led emergency lighting.

3 LM317 Calculator

This calculator helps you set the output voltage of LM317
regulator IC by simply replacing the value of both R1 and R2.
The value of R1 usually varies from 100 t0 1000 ohms while
R2 is of any value and preferably a trimmer type or potentiometer.




The output voltaged desired can be calculated using this formula.

Vout = Vref*(1+(R2/R1))+ (Iadj*R2)
where Vref = 1.25V and Iadj = 100uA.

The first calculator allows you to set the value of both R1 and R2
to determine the output voltage regulated by LM317.
The next calculator allows you to set your desired output voltage and
value of R1 to determine the value of R2.

lm317 regulator

R1 resistor	R2 resistor	Output Voltage
Voltage out	R1 resistor	R2 value

1 simple power supply for microcontroller

This power supply uses 7805 regulator IC. It can deliver
up to 5W of power to microcontroller and its peripherals.
It has a 5V regulated output, suitable for microcontroller operation.

power supply schematic diagram

Power supply materials:
1. C1-1000uF/ 25V
2. C2 220uF/10V (optional)
3. LM7805 regulator IC

7805 IC pin outs

1 Cheap Microcontroller Power Supply

This project is a Cheap Power Supply for microcontroller. 

It is composed only of a transistor and zener diode that regulates

the output voltage to about 5V (within 2.5 to 5.5V voltage range

of microcontroller).

Power Supply schematic diagram

It can regulate up to 500mW of power, which large enough to 

power a microcontroller of both PIC and ATMEL. The incoming voltage

can be from a battery or a converter.

Power Supply materials

1. C - 1000uF/16V electrolytic cap

2. R1 - 1.2-ohms/0.5W resistor

3. 1kilo-ohms 0.25-0.5W resistor

4. zener - 5.6V zener (1N5232B or 1N4734A)

5.NPN - general purpose npn transistor (2N2222 or 9013)

note: do not use this power supply if you are requiring more than 500mW.

0 TRANSFORMER AND INDUCTOR DESIGN HANDBOOK

TRANSFORMER AND INDUCTOR DESIGN HANDBOOK
by COLONEL WM. T. MCLYMAN

Contents

Chapter 1
Fundamentals of Magnetics
Chapter 2
Magnetic Materials and Their Characteristics
Chapter 3
Magnetic Cores
Chapter 4
Window Utilization, Magnet Wire, and Insulation
Chapter 5
Transformer Design Trade-Offs
Chapter 6
Transformer-Inductor Efficiency, Regulation, and Temperature Rise
Chapter 7
Power Transformer Design
Chapter 8
DC Inductor Design Using Gapped Cores
Chapter 9
DC Inductor Design Using Powder Cores
Chapter 10
AC Inductor Design
Chapter 11
Constant Voltage Transformer (CVT)
Chapter 12
Three-Phase Transformer Design
Chapter 13
Flyback Converter, Transformer Design
Chapter 14
Forward Converter, Transformer Design, and Output Inductor Design
Chapter 15
Input Filter Design
Copyright © 2004 by Marcel Dekker, Inc. All Rights Reserved.
Chapter 16
Current Transformer Design
Chapter 17
Winding Capacitance and Leakage Inductance
Chapter 18
Quiet Converter Design
Chapter 19
Rotary Transformer Design
Chapter 20
Planar Transformers
Chapter 21
Derivations for the Design Equations

download transformer and Inductor design Handbook

10 simple touch switch using transistor

This  circuit is no doubt one of the simplest touch switch circuit
using transistors configured in a Darlington form. When you touch
the touch plate, your hand will provide a several ohms of resistance
that is enough to make a close circuit between the base of the
transistor and power supply. Touching the plates lights the LED
up but it will automatically tuns off when plate is not touched.

Materials:
2 - general purpose transistor (9013, 2N222, others)
1 - 100k resistor 1/4 W
1 - 100 ohm resistor 1/4 W
1 - 6V to 9V battery
1 - LED (preferably red)

Note that  this touch switch circuit may not work properly when

the supply is a rectified dc from an ac source.

3 touch alarm circuit using 555 IC

This touch alarm circuit will sound when somebody touches the trigger plate. This plate can be place in any metal such our doors or in metal knobs. It can be use as your simple burglar alarm or security circuit that can place in your doors.

touch alarm schematic

Touch alarm circuit operation
The heart of this alarm circuit is the 555 timer  that is operated in monostable mode. The timer produces an output sound to buzzer with the time delay constant equal to 1.1RC.When the voltage at the trigger pin of 555 IC (pin 2) reaches below 1/3 of the supply voltage, the output will be high with the duration of 1.1RC. For 3 seconds duration, R is 12K resistor while 22k for 5 seconds. You can use 555 timer calculator for your delay options. The circuit is very similar to Simple Touch alarm and sensor.

Touch alarm materials:

Part list

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Simple-electronics.com gives no warranty that all materials presented here are correct, safe and accurate.
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Copying any material here is allowed provided you link back to simple-electronics.com

2 Broken Fuse Indicator using LED and transistor

Sometimes we found ourselves in great difficulty troubleshooting an
equipment. The funny thing is, upon spending so much time in front of
a defective circuit, the problem is only a broken fuse.

This simple project has a visual indicator in a form of LED
that help us know that the fuse is broken.

blown-fuse indicator schematic

This indicator circuit consists only 4 electronic components :
1. general purpose PNP transistor (ex. 9012,2N3906, others)

NPN transistor pins

2. LED or the light indicator

LED pins

3. general purpose silicon diode (1N4001, 1N4007, others)
    the cathode or negative is with white or gray band.

silicon Diode

4. 0.25W 100kilo-ohms resistor for transistor biasing.For resistor color
    you can use online resistor color code calculator.

100k resistor

Note: 
The broken fuse indicator circuit can only be used with an input voltage
ranges from 6V to 15V dc.

19 LED flasher circuit using 555 IC

This project is a flashing led circuit powered by 555 timer IC.This

flasher circuit is composed of two versions, the simple led flasher 

that uses only two LED, and big flasher that consists 20  LEDs.

Simple LED Flasher circuit is powered from a 6V to 12V

battery and delivers a current of about 20mA to LED. The 

frequency of the flashing on both LED is controlled by 100K

potentiometer connected between the discharge and trigger pin

of 555 timer IC. The rate of flash ranges from 1blink per 2 

seconds up to 10 flashes per sec.

simple LED flasher schematic

Big LED flasher circuit is composed of 20 LEDs and uses transistors

as the driver and amplifier of the pulses generated by the 555 IC. The 

npn  general purpose type (9013, 2N222, etc), so is the pnp transistor

(9012, BC557, etc) If the supply voltage is 6V, R1and R2 =27 ohms 

while R1 and R2 = 200 ohms if supply voltage is 12V.

Big Led Flasher schematic

You can change the frequency of the flashes by changing the values

of resistors and capacitor using the 555 timer calculator.

If you planning to build up to 300 LED per group just replace the part of the schematic above with this. See diagram below. Power supply used is 12V.

Note: The type of LED can be of any color such as red, green, orange, yellow but not blue or white LED.
          Blue or white LED requires much higher forward voltage to light.

0 simple iPod charger using 6V to 9V battery

This simple ipod charger is powered by a 6V battery or a 9V battery.
This charger is easy to construct even by a non-electronic inclined
person.The charger delivers 150mA to 200mA current to you cellphone
or iPod.

6V to 9V charger schematic

USB pins

The positive output of the charger is connected to pin 1 of the USB while
the charger's negative output is connected to pin 4.


Charger part list :
1. R1 is 390 ohms for 6V or 1.5K for 9V battery
2. Zener diode is 4.7V rated 1W
3. Transistor is any general purpose type

7 Simple FM transmitter powered by 1.5V battery

This simple  FM (frequency modulation) transmitter is powered only by a 1.5V battery and uses only 1 transistor.The frequency of this transmitter is controlled by the L-C resonance circuit and operates from 80 to 110 MHz.

simple FM transmitter schematic

The inductor L1 is made of 8 turns of  #22AWG magnetic wire wound  with the diameter of 4-5cm or diameter of a pencil. The antenna is a 6 inches copper wire connected at the middle of L1 inductor. Other parts

are not critical and can be replaced by its closest value. Resistor are 1/4 watt type and capacitors are ceramic except  the 10uF electrolytic  capacitor. 5-60pF capacitor is a trimmer type or variable type.

Note: Modifying this simple fm transmitter circuit such as increasing its power capacity is illegal.Review the fcc limits regarding fm transmitter if you are planning to build a more powerful one.

Notes by Acme Fixer:(Thanks!!)
1. Add 0.01uF capacitor across 1.5V supply near the transistor.
2. You can remove the antenna.
3. Mic is an electret condenser microphone type.
4. See the rest of his recommendation based on his experience in building the circuit. See comment section below.

7 cellphone call detector using 555 timer

This simple project uses a 555 timer cmos type. It detects an incoming  call from your cellphone by. The output LED will blink when the inductor detects signal from your cellphone. This detected signal is feed through the transistor
an then triggers the 555 timer IC.The voltage output of the timer is then doubled by the 220uF capacitor and
1N4001diode combination.

cellphone call detector schematic

The timer IC used is a CMOS type, inductor is made of  120-150 tuns of #28 magnetic wire wound in a
5cm diameter. All other parts of this project are not critical and can be replaced to its closest value.

4 Clap Activated Relay or Switch (220V)

This Clap Activated Relay project is similar to clap activated LED lamp. The only difference is you can power
up a 220V lamp  or any 220V equipment using a relay.

220V clap relay switch schematic

The transformer is 220V to 15V -0V-15V transformer of a minimum of 10VA. You can replace the 1N4001 diodes of any types with similar ratings.The relay  is 12V with 5A output current capacity or higher. You can replace also the transistor of any general purpose type.

Note: This clap activated relay   is connected to main supply (220VAC). Do not try to touch the main supply to avoid electrocution or do not try to construct if you do not have any idea in electronics.

7 Clap Activated LED lamp

This 12v Led lamp is clap activated. You can turn on and off the lamp by simply clapping your hands or dropping a book to ground.

Clap activated LED lamp schematic

First the electret microphone picks up a sound from a clap or any sound that mimics a clap then amplify it  using the first 2N222 transistor .Then the flip-flop circuit composed of two 2N222 transistors (form a mirror circuit)  will on and off the output transistor in every clap. Parts of  this project are not critical, you can replace the transistors any general purpose type. Output LED are either white or blue.