Latest Electronics Projects to Build PDF Ebook

Contents
BY WWW.CIRCUITDIAGRAM.ORG
• Door Left Open Indicator Alarm
• Digital Variable Resistor
• Cold Sensor Switch Using LM35 & CA3140
• Simple Loud Security Alarm Using PIR Sensor Module
• LED Thermometer with Selectable Temperature Switch
• Home & Office Basement Flood Alarm
• Motion Sensing Main Gate Night Light
• Contact Less Mains Power Failure Alarm
• Motion Sensor Solar Outdoor Light
• Automatic Washroom Light
• Simple Automatic Emergency Light
• Single Chip Light Dark Sensor Switch
• Automatic Sequence Solar Battery Charger
• Touch Activated Switch Using 4011 IC
• Multiple Style Flasher Using 555
LATEST ELECTRONICS PROJECTS TO BUILD
FREE EBOOK BY WWW.CIRCUITDIAGRAM.ORG
PAGE 01
For More Latest Electronics Projects Visit:
www.circuitdiagram.org

About This Book
This free eBook is a joint effort of circuitdiagram.org team for electronics students, electronics
engineers and electronics hobbyists to provide latest & working electronics projects that uses low
cost, reliable and easy to get components.
This book contains some of the very useful electronic projects, which can be built in one or two
hours if all components are available with you. You can also make changes in these projects to
make them according to your requirements or use them with your big electronics projects. These
projects can also be connected with microcontrollers for further enhancements.
This free book is produced by Circuitdiagram.org, www.circuitdiagram.org is an educational
website which provides free electronics projects, there are hundreds of latest designed electronics
projects are on the website and new circuits / projects are added frequently. You will find many
categories of electronics projects / circuits on the website which are audio circuits, power supply
circuits, battery charger circuits, test & measurement circuits etc.
For more latest electronics projects please visit www.circuitdiagram.org and do not forget to visit
the website often to get the latest added electronics projects.
Published on April, 2017
PAGE 02
WWW.CIRCUITDIAGRAM.ORG

Door Left Open Indicator Alarm
Electronics technology is helping us in every part of life and as this technology is growing day by
day it is making our life easier & better. It is solving many issues & problems of our life and in
these issues one of the main issue is security. The uses of electronic security devices
increasing because every one wants to be secure and wants security of their homes, cars, offices
etc.
The simple circuit diagram shown here will also serve for a very useful security
related purpose. It will alert you by a melodious alarm when you forget to close the door after a
preset time period.
The circuit can be used for any of your door for example your home door, office door, garage door,
store room door or even your lockers and cupboard doors.
PAGE 03

Digital Variable Resistor
This is a circuit diagram of digital variable resistor, the circuit can be used to replace analog
variable resistor in any desired electronic circuit, therefore it can be used to adjust the value of
resistance by pushing a button or digitally adjust connecting it to microcontroller, this procedure
replaces the need of manually hand adjustments by the user.
The circuit is very easy to build and using low cost ICs and components. The operating voltage of
the circuit can be any from 5V to 16V DC. It can also be operated with 3V, and if you want to
operate with 3V just replace the NE555 IC with its low voltage CMOS version 7555 or LMC555
etc.
PAGE 04

Cold Sensor Switch Using LM35 &
CA3140
Like heat sensor a cold sensor circuit can also be made using almost same components which is
used by heat sensor. The circuit diagram of cold sensor switch using LM35 & CA3140 shown here
can be used to control AC and DC devices on desired cold temperature.
The LM35 temperature sensor IC is used to detect the temperature. The CA3140 is an operational
amplifier & it is working in comparator mode here. The circuit can be operated with any voltage
from 5V to 12V DC. Make sure to use the relay value according to the operating voltage.
PAGE 05

Simple Loud Security Alarm Using
PIR Sensor Module
This is a circuit diagram of simple loud security alarm. This circuit can be used in any room or
outside area. The circuit will make a loud alarm when the PIR sensor module used in the circuit
will detect the presence of any person or animal in its detection range.
The circuit uses a ready made PIR sensor module that can be easily purchased from your local
electronic store or from any reputable online electronic store. This ready made PIR sensor Module
also contains a variable resistor to set the time period of output after sensing an infrared. The
operating voltage of the circuit is 5V to 12V DC.
PAGE 06

LED Thermometer With Selectable
Temperature Switch
Here is a very useful project of a LED thermometer with selectable temperature switch. The
circuit contains two different functions which are temperature sensing with visual indication
through LEDs and another function is it can also control any AC/DC device or appliance on the
desired selected temperature.
A 10K NTC thermistor is used as a sensor for temperature. 10 LEDs are connected at the output of
LM3914 IC. LM3914 IC contains 10 separate opamps and each LED is derived by a separate
opamp. The point marked IC connection in the circuit diagram can be connected with any desired
pin of the IC from which any LED is connected so it will switch on the relay switch on the desired
temperature.
PAGE 07

Home & Office Basement Flood
Alarm
The figure below shows a very useful project of home & office basement flood alarm that will
indicate if water enters in your home or office basement. The circuit makes an early indication so
the user have much time to stop the water before it enters in the furniture or in electronic
appliances. The circuit is very easy and can be built with in one hour if you have all the
components at your table. A UM66 melody alarm circuit is connected at the output which will
become activated when the two sensors shown in the circuit will detect water.
The two sensor points shown in the circuit diagram should be attached where there are most
chances of water to come first or you can also attach it on multiple location by simply attaching
more wires with it.
PAGE 08

Motion Sensing Main Gate Night
Light
Here is a very useful project of a motion sensing main gate night light circuit. The circuit will
switch ON the mains gate light of your home when it will detects any person in the range of the
PIR sensor. It can be very useful for security purposes or it can also be used as a power saver by
switching on the lights only when it is required.
The circuit is very simple and easy to build. It is using very few components, It is also using a
ready made PIR sensor module which can be purchased from any local or a reputable online store.
The circuit is also using a dark sensor circuit that will only switch on the circuit at night, so after
building the circuit adjust the 100K variable resistor to activate the circuit at night.
PAGE 09

Contact Less Mains Power Failure
Alarm
This is a circuit diagram of contact less mains power failure alarm circuit that will automatically
activate and produce an alarm when the mains power goes off. The circuit not require any
connections for detecting the mains voltage. It will sense it wirelessly through EMF (Electro
Magnetic Field) that is build around the AC wires. The 1M variable resistor is used to adjust the
sensitivity of the circuit to detect the EMF. The antenna wire used in the circuit should be 4 inches
in length.
The circuit is also using a separate supply from batteries and it can be operated from any battery
from 4.5V to 12V. The circuit will use very less current in consequent mode therefore the batteries
will last very long and you don’t need to change them very often once it is placed with the circuit
at any place where you want detect the power failure.
PAGE 10

Motion Sensor Solar Outdoor Light
The figure shows a motion sensor solar outdoor light project. It will charge a 1.2AH lead acid
battery from solar panel and only activate the output LEDs when it will detects a person in front of
it or else it will remain in off mode. This function saves the battery a lot and also provide very
bright lighting of four 1watt LEDs.
Once the PIR sensor detects a person then its output goes high which lit up the LEDs for a preset
time period, this time period can be set with the build in variable resistor in the PIR sensor module.
PAGE 11

Automatic Washroom Light
This automatic washroom light circuit will activate the light only when it is required. The circuit is
actually a vibration sensor that can sense the vibrations of the door which will produce when some
one touch the door to open it.
A peizo sensor is used in the circuit to sense vibrations, for best results use long wire between
peizo sensor and the circuit and place the peizo sensor on the door and rest of the circuit should be
placed where it will not come in contact with water. Operating voltage of the circuit is 5V to 12V
DC, you can also use any plug pack of output voltage between 5V to 12V DC. The relay value
should be choose according to the operating voltage.
PAGE 12

Simple Automatic Emergency Light
An emergency light is a very useful device to switch on immediately when sudden mains power
outage is happen. The circuit is using very few components and it will switch on automatically
when the mains power will go off.
The circuit is using four super bright white LEDs which produce enough light to light a single
room. As shows in the circuit diagram the circuit is using 3 1.5V AAA batteries as backup, when
power outage will happens the circuit will automatically shift to the AAA batteries. In the presence
of mains power the circuit will be completely disconnected with the batteries due to which the
batteries will last longer.
PAGE 13

Single Chip Light Dark Sensor Switch
This topic describes a single chip light dark sensor switch using a LM358 IC, the circuit can be
used to control any AC and DC devices in both situations i.e. light or dark. Two separate relay
switches are connected at the output of LM358 IC.
The sensitivity of the circuit to activate the relay switches on desired light and dark levels can be
set by the two 10K variable resistors which are VR1 and VR2. The circuit can be operated with
any voltage from 5V to 12V DC. The relay values should be used according to the operating
voltage. Let say you want to operate the circuit with 5V then use a 5V relay and if you are
operating the circuit with 12V then use a 12V relay.
PAGE 14

Automatic Sequence Solar Battery
Charger
Solar panels are best source of free green energy and if you want to build a smart solar system
which also saves the wasted energy of solar panels then this circuit is ideal for your. Solar panels
charge batteries in the sunlight but a charge controller device or circuit is also required between the
solar panels and batteries which disconnects the batteries from solar panels when they are fully
charged. Some times the batteries are charged quickly (in few minutes or hours after the sun rise)
due to not much usage by the user and the charge controller disconnects them from solar panels.
When the batteries are disconnected from the solar panels in the day time the solar panels still
generates energy which gets wasted. The automatic sequence solar battery charger circuit shown
here will over come this problem by shifting the solar panels output to the next battery
automatically. More details about this circuit can be found on this link:
http://www.circuitdiagram.org/automatic-sequence-solar-battery-charger.html
PAGE 15

Touch Activated Switch Using 4011
IC
Here is a project of touch activated switch using 4011 IC. As you can see in the circuit diagram
there are two touch points which are touch point 1 and touch point 2. When user touches the touch
point 1 the output of the 4011 IC goes high as a result the 2N4403 transistor will goes in ON state
and current starts travel to the relay through the transistor which will activate the relay switch.
And in opposite condition when the user touches point 2 the output of the 4011 IC goes low, hence
the transistor goes in OFF state which disconnects the current going to the relay and as a result the
relay become deactivated.
PAGE 16

Multiple Style Flasher Using 555 IC
This project of multiple style flasher can be used to blink the LEDs in different styles. The blinking
patterns can be changed by adjusting the 3 100K pots in the circuit. The number of LEDs can also
be increased, for doing so connect three LEDs in parallel with a 75 ohms resistor as shown in the
diagram.
The circuit is built around three 555 timer ICs. The max output current of a 555 timer IC is 200mA
therefore you can drive 20 to 30 LEDs with each 555 IC. The operating voltage of the circuit is
12V DC.
PAGE 17

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