Deep dive into the space of Electronics— Part 1

Adhish Velingkar
12 min readFeb 6, 2022

Welcome to my very first tech article !!!

First of all, before starting the topic, since this is my new venture in writing and for that, I would like to mention something about myself which has motivated me to write such an article and for this, I would like to thank my parents whom I look up to for everything — be it maintaining discipline, time management, or their strive to discuss the cutting edge technologies even at an age of 50+.

Accountability

This may sound boring right now, where I am discussing manners and personal well-being instead of tripping out and partying at the age of 23, but yeah! It is what is and I believe that one should follow this practice often be it in a college or corporate organization, which leads me to summarize this topic in short with a personal quote that I made during one of my audit courses while learning about the operations of product development. Here is the quote: “Always go for a variable change”

My multipurpose table — Study-Experimental area

As a budding Electrical and Computer Engineer, I was fortunate enough to study the basic concepts that we see and use in our daily life, such as a car or a mobile phone which included subjects like Analog-Digital Electronics, Integrated Circuits, Electrical Systems, Microcontrollers, Wireless Systems, RTOS, & Image Processing that has enabled me to test my fundamentals with its appropriate mix of theoretical and practical courses. But I believe that learning about these notions during my undergraduate years was just the tip of the iceberg as it missed one of the core factors i.e. ‘Application Level’ understanding which is generally needed to build the foundation and set up the vision while learning a particular topic.

Demonstration is Necessary

I can still remember where me and my classmates in my junior years used to keep on wondering (like Mr Bean) about what kind of circuits, mesh analysis, components, etc. needed to be selected while solving a particular problem statement or doing lab experiments during the internals.

IC - Radio Filters and Antennas — VLSI

Realizing about this at an early stage, I felt that study on the subject would be unwarranted without any formal experience and that is why I decided to intern in an industrial environment during my summer vacations which instilled in me a great sense and exposure towards today's consumer electronics and hardware market and their application fields in real life. Here, I am highlighting application fields because as ECE students we normally forget or miss out on the purpose of where to use a transistor (NPN or PNP) or a diode or rectifier or any other related components.

I would like to elaborate on this by sharing my personal experience, which has helped me to understand the subject better when I was interning on a power electronics project. For those who don’t know Power Electronics: It is the branch of electrical engineering that deals with the processing of high voltages and currents to deliver power that supports a variety of needs. From household electronics to equipment in automotive, space applications, these areas all need stable and reliable electric power with the desired specifications.

Prerequisites for this were understanding of Analog-Digital electronics, Integrated Circuit Design, and Simulation tools, out of which as a 2nd year BTech student I was aware of each module in bits at that time but I never knew where and how to use them in the real world and this internship really helped to improve my imagination skills which I couldn’t figure during my coursework time. When I say this, it does not mean that one won’t be able to understand the subject if he/she are not getting any internships. As in the end, it depends all on the skillsets that you own and not on which brand you work for. Taking internships is just a recommended practice, otherwise one can take part in the technical student communities by self-learning on various assignments and participating in competitions.

Now, as an ECE student, I can completely relate to the following figure of speech:

“Jack of all trades, Master of none”

My curriculum itself is an amalgamation of different fields in which I got the opportunity to explore each domain deeply.

But in the end, it depends on the individual who likes to shape their career according to the specialisation(majors) they opt for.

Looking at the current pandemic situation around and the conduction of Online classes seems to be boring and disinteresting that might end up their semester by missing out on some important points as discussed above and this is what motivated me to take some time out during my weekends in which I can share some of my methodologies which I used to follow during my undergraduate years while studying particular subjects and plus it gives me a revision as well !

Thus, I hope this will help to develop a sense of excitement while reading a book and exploring the relevant content to it.

As the topic itself says ‘Deep Dive into Electronics’, and after reading my views on application-level understanding and mentioning some typical subjects in engineering, I guess you must have figured till now that what I am going to talk about…Well if you haven’t yet then why to wait for it, let’s get straight to the topic:

Electric Flyswatter(a.k.a Mosquito Killer Racket)

Electric Flyswatter Bat — Slide & Push Button Combo — AC charge storage

Prerequisites: Concept of analog electronics, electrical components and laws.

Definition and Uses:

Mosquitoes are a huge threat to humankind and these are found in each nook of the world. A cool manner of avenging yourself should be via way of means of casting off those “insects” through electrocution. A mosquito swatter bat is designed only for this

As you can see in the above three figures, a mosquito killer bat is likewise known as an electric powered flyswatter, mosquito bat, racket zapper or zap racket. These gadgets are handheld and look similar to badminton rackets or tennis rackets.

Inside the mosquito killer bat, it consists of an electric-powered accessible battery and a circuit board. The circuit is made with an electric-powered oscillator, a step-up transformer, a voltage multiplier, and a charging unit that charges the electrical battery.

Now let us see how the circuit in the racket works:

General Circuit Schematic

Working :

Above is the internal circuit diagram of the bat. The total circuit is can generally be divided into 3 stages, namely the power supply/charging circuit for the battery inside, the oscillator/transistor stage and finally the voltage booster stage.

Note: Mostly the schematics remain the same with a few minor changes which may change from manufacturer to manufacturer.

Principle: The mosquito bat will be activated by pressing the power button after the sliding switch is in the ON position. When the sliding switch is in the OFF position, the push button is disabled.

The grid of the device is then electrically charged, a fly/bug/insect nearly bridges the gap between electrodes, a spark jumps through the fly and high voltage burns it. The final capacitor in the voltage multiplier circuit discharges when the circuit is shorted by a mosquito.

The below figure shows the retractable plugs (in white with toggle switch) through which AC input is given. In addition to this, the functional operation of the bat consists of a sliding switch and push button switch which works hand in hand for the activation of the mesh circuit as seen in previous figures.

AC Retractable Plugs and PCB Design

The PCB used has one layer. The board appears to be manually assembled, with through-hole (TH) mounting type components placed on one side and then hand soldered on the other side, where the copper traces are visible.

Mesh Design by Injection Moulding
Mesh Design

The mesh metal material is aluminium, which is a good electrical conductor. The mesh assembly consists of two orange plastic enclosure parts, three metal wire meshes that serve as the terminals, and two white separators that are sandwiched between the mesh to ensure that the mesh does not short.

Circuit Teardown in Parts:

Charging Circuit

a) Power Supply/ Charging Circuit
A mosquito killer bat circuit receives strength from an electric powered accessible battery. Therefore a charging circuit is needed to charge the battery. This form of the circuit is called the transformerless charging circuit or capacitive charging circuit. After a complete charge, the battery works for five to eight hr as per user. It’s a simple capacitive power supply that can source a few milliamps sufficient enough to charge the battery inside. The initial capacitor helps in limiting the current and then the voltage is rectified. This rectified voltage is brought to the desired level (battery voltage level) using a Zener Diode and a capacitor to filter the noise on the DC voltage produced. This would charge the battery inside when plugged into mains. This may be accompanied by a switch to enable charging.

Note: Refer to the below site for more clear understanding of using rectifier circuits.

Voltage generation & Voltage Multiplier Circuit

b) Voltage Generation-Oscillator stage

A high voltage generator circuit is the most important part of the mosquito killer bat circuit. This circuit converts the low DC voltage to high voltage AC voltage about 200 to 230 V. The joule thief concept (Wikipedia reference) is used in this inverter circuit, wherein only a single NPN transistor and a centre-tapped transformer execute sustainable oscillation across the two winding of the transformer.

Current is enabled through a transistor(generally NPN) which allows the current to flow through a primary coil, inducing a voltage in the secondary coil and the secondary coil in return induces a voltage in the feedback coil.

Note: Refer to the below two articles for selecting the type of transistor and getting to know the basics of a step-up transformer

This counter voltage in the feedback coil causes the transistor to stop conducting and the magnetic field in the ferrite core to collapse via electrical energy from the secondary coil. This process helps the transistor to conduct again, repeating the process and creating pulsed DC. The changing magnetic field induces a high voltage in the secondary coil. The voltage induced in the secondary coil depends on the ratio of the number of turns of Primary and Secondary winding. This voltage will be in the order of a few hundred or thousands.

c) Voltage Multiplier Circuit

As we see high voltage generator circuit converts the voltage from about 200 to 230 V, which could not build up the required voltage to create the spark between two electrodes in the mosquito killer bat.

Therefore a voltage multiplier circuit is needed to step up the voltage. Typically, the circuit uses voltage triple, which triples the available voltage from the secondary winding of the transformer.

This high voltage is passed onto the wire mesh of the bat. Out of 3 layers of the mesh, the outer two layers are connected to -Ve/GND and the inner layer is connected to the generated high voltage. The distance between the meshes will not let the high voltage arc off on its own. But when mosquito/bug flies in between, it helps in the information of low resistance path, which results in arcing through the body of the mosquito.

Thus, this is how an electric fly swatter circuit works in all.

SHAZAM!!!!

If you have reached this part of the article, then I am pretty sure that you must have figured out, why I wanted to correlate the coursework and the application understanding in parallel.

Can Mosquito bats damage the health of human beings?

  • For safety reasons, many mosquito bats have a three-layer grid to prevent people from touching as mentioned above in the mesh design of the circuit.
  • The maximum continuous flow of most electric flyswatter is less than 5 milliamps (mA) current after the initial discharge. This secretion is safe, even when flowing from one arm to the other.
  • As one can often see notice on railway platforms about high voltage transmission lines with a danger sign, it is said because a normal person can experience a shock only when the voltage and current are at their high rates. If the voltage is high but the current is very low in its comparison then it is safe, but if both the quantities are high, then the individual can surely be in danger.

Miscellaneous:

Stun Gun vs Taser

This electric flyswatter circuit is much like the one found in a taser or an electroshock weapon/stun gun, however, the output voltage of the mosquito bat is much lower and hence cannot kill the person.

Some people think stun guns and Tasers are one and the same. The truth is that they’re two very different but very effective weapons for self-defence, to use in two very different kinds of situations.

Comparison of Stun Guns vs Taser Guns

Stun Gun: A stun gun is a very small device that is made to carry along with you in a bag, pocket or purse. They can be disguised to look like lipstick, a flashlight, or even a cellphone. The basic idea of the stun gun is that several small prongs are activated inside the device, and when you hit the oncoming attacker, the prongs send electricity to the bad guy rendering the attacker temporarily knocked out with pain.

Taser Guns: The Taser’s basic premise is almost exactly the same as a stun gun for self-defence. When you hit an attacker or target, it sends electricity through two prongs to stun or disorientate them. The only difference is that instead of jabbing the two prongs into them, you shoot the prongs instead. Inside every taser is a compressed gas cartridge, and when you shoot a taser, the gas cartridge explodes and fires out two wires with prongs at the end. As soon as the prongs latch on to the target by their clothes or skin, it sends electricity through the wires and into the prongs to electrify the target.

Conclusion:

Hence after studying about this particular product and correlating it with the subjects such as Analog Electronics, Basic Electrical Engineering shows a clear demonstration of the topics and their application area.

Well, here is the end of my first article.

Stay tuned(next weekend) for the 2nd part of this article where I will talk about some other applications.

Thank You!!!

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Adhish Velingkar

A novice blogger who talks about Power-Analog Electronics, EV's, Low Voltage devices, Embedded interface, Hardware-Simulation, Renewables, Electrical Designs