A Guide to Circuits with One Equation

I wanted to do this blog because when I was younger and my interest in circuits was growing, I did not have a lot of math background that I could apply to my creations. Whenever I looked at online resources and textbooks, I found that they were often confusing and very math intensive. That isn't to say that building some circuits doesn't require some advanced math. In fact, most of the consumer electronics we use are so advanced that an electrical engineer would be needed understand the math behind them. Through my time designing projects I have discovered the concepts, requiring no more than multiplication/division, that are most important to understand in order to build some basic circuits.

The Electricity/Water Analogy

There is a reason that this analogy is used in various textbooks for introducing concepts of electricity to new learners. The electricity/water analogy relates this new idea to something we are familiar with: flowing water. Think of every water droplet as an electron. The water pressure is considered the electric voltage (measured in volts), the water flow is the current (measured in Amps), and a blockage in the hose is resistance (measured in Ohms). The equation I am listing below is the most basic equation for circuitry:

Voltage / Resistance = Current

(water pressure) / (blockage) = (water flowing)

This equation can be rewritten multiple ways but I like to show it this way because current is dependent on the voltage and the resistance. Lets say you have a hose with high water pressure and no blockage. Since the "voltage" is high and the "resistance" is low, based on the equation there will be high "current" and lots of flowing water.

Now, if some blockage was introduced to the hose line and the water pressure was kept the same, the flow of water would decrease. Furthermore, if the water pressure was increased and the blockage was kept the same, more water would flow.

Now if we were to think of this in terms of electronics, it should make a little more sense.

We now have a battery hooked in a loop with a resistor, a component that provides "blockage" in the wire", and a light bulb (LED). The LED needs 5 volts but on if it is given too much current it could break (think of it is as a pipe bursting because of too much water). To decrease this flow we provide the resistor, which allows just right amount of voltage and current. The current required for this led is around 20 milliAmps (20/1000th of 1 Amp). Using our equation, this would give us a resistance with the value of 250 ohms. The final circuit would look something like this:

Note: I used a resistor with the values close to, but not exactly, 250 ohms.

I hope everybody learned something in this introduction to circuits! Below I am providing a link to a video that is a good visual of the water/electricity analogy.

https://www.youtube.com/watch?v=BoRlclML3tE

An In-Depth Look into Wireless Charging

For my very first blog post I thought it would be appropriate to focus on a device that is upcoming in the technology industry and growing in popularity, yet very few people know how it works:

Wireless Charging.

The theory behind wireless charging goes all the way to Nikola Tesla with his invention of the "Tesla Coil" and the formation of a concept called "induction." Induction is, to put simply, a way to convert electrical current into magnetic fields and vise versa. Every wire that has current running through it, such as an electrical cord, has a magnetic field surrounding it. However, when these wires are coiled in a tightly bound loop as you would find in wireless chargers, the current is able to form a much stronger magnetic field running through the coiled wire.

Now for something to take the energy from that magnetic field and turn it into a current, it would also need to have a coil of wire. This is why in all of the new phones that support wireless charging have these coils of wire on the inside of them. The magnetic field that produced by the charger is received by the coil in the phone and then turned into electricity that the phone can charge its own battery off of.

Now some of you readers may be thinking, "So if our phone has a wired coil and battery, then would it be possible to charge other devices with our phones." That assumption is completely correct and many companies, such as Samsung with their phone the "Galaxy S10" support a feature known as power sharing. This allows for phones with this capability to share power between each other without using any type of cable and instead using induction! However, this is currently not a supported feature with any of the iPhone products and as of right now, they only support wireless charging, not wireless sharing.

This technology is quite far from hitting its full potential. Currently, there are many different companies designing ways to expand this technology. On the channel Linus Tech Tips, they feature a device that screws into a light bulb fixture and is able to wirelessly charge various items in a room from meters away. I will provide the link to the video because it is a very cool application of wireless charging but I will also give the disclaimer that there is some swearing through portions of the video: https://youtu.be/YeNXRD8eziA

Personally, I would never try or recommend designing something like this at home because safe wireless chargers have precautions in the circuit design and are made by professionals. If you are further interested by the concept of wireless chargers and how one is made, Robin Mitchell does a good job of taking one apart and explaining the parts that he finds. The link is down below:

https://www.allaboutcircuits.com/news/teardown-tuesday-qi-compatible-samsung-wireless-charger/

As for my next blog post we will be getting into working with the basics of circuits and you too will be able to design you own!