Learning basic electronics for beginners is the primary goal of this site. Controlling a light or LED is one of the simplest circuits to learn. The electronic principles that you learn while studying such circuits, apply to all electronic circuits.
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Simple circuits introduction:
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- Power supply provides voltage and current. Batteries use chemical energy, whereas generators move wires past magnets. Generators provide the power to your house, which you can plug adjustable DC adapter power supplies into.
- Load usually does something useful (emit light, turn a motor, creates sound, etc.) with voltage and current (power). The load also always creates waste heat.
- Conductors transfer voltage and allow current to move easily.
- Insulators block voltage and current.
Affiliate link ad of a power supply used in my videos. There are larger ones that are cheaper if portability isn’t important. I primarily got this one because I can easily film it next to my circuits while making my YouTube videos.
Most of electrical and electronics projects these days involves buying prebuilt systems or easy to wire systems, some examples are…
- Solar panels.
- Battery banks.
- Arduino: A kind of user programmable mini computer made to connect directly to circuits/modules.
- Circuit modules.
- Boost converter.
- Buck converter.
Learning basic electronics will help you make better choices in your electronics purchases, and maybe some day you will build things from scratch with basic components for fun, or because what you want isn’t available otherwise.
Basic electronics introduction:
You need to be familiar with basic circuits before you will be able to understand more complex circuits.
Above is a drawing of an LED (Light Emitting Diode) protected by a series 470 ohm current limiting resistor.
- Resistor protects all of the components of this circuit from overheating by limiting current.
- LED and resistor are powered by a 9V battery.
- Resistor power = waste heat.
- LED power = light, and some waste heat.
- The components are all temporarily connected together on a prototype breadboard. The 9V battery snap, which provides the battery with wires connected to the battery terminals, usually has stranded wire (a bunch of tiny wires) which I twist into a spiral so that they will plug into the breadboard better. Stranded wire bends easier than a solid wire.
You will rarely see a drawing of a breadboard circuit. There’s a chance that you will see a pictorial like the one shown here.
You will most likely see a schematic diagram of the circuit.
I added to the schematic some important information to be aware of when it comes to the circuit.
- Supply/Battery voltage (usually shown on schematics).
- Resistance value (usually shown on schematics).
- Estimated voltage across the resistor and the LED if it has a 2 volt forward voltage (Not usually shown on schematics)
- Circuit current, which is the same through all series components and connectors. May indicate an actual meter measuring current at that point. (Not usually shown on schematics).
Electrical properties to be aware of:
- Voltage: Electric potential. Batteries and electrical outlets have voltage that you can use to power a suitable load.
- Current: Moving charges/electrons flowing. Pushed by the voltage of a power source, and limited by a load.
- Resistance: Opposition to current.
- Semi conduction: Components that conduct more or less depending on voltages and/or currents involved and in which direction the voltage is applied (polarity). Exactly how is specific to each particular type of semiconductor component.
- Wattage: Work done, such as the heat that is generated. Calculating wattage (P) is done by taking the voltage (V) across a component times the current (I) through the component. P = V x I
- Power loss and efficiency: Usually referred to when converting power (Input versus output), but can also refer to how much of the total power is being consumed as waste heat.
Primary goals when building/designing a circuit:
Whenever studying a new circuit, try to make sure you understand how every part of the circuit contributes to these 2 goals.
- Don’t let any part of the circuit overheat (wattage).
- Use components that provide the desired outcome.
Visualizing electric current:
Current runs equally through all series (connected end to end) components and the power supply. The current is pushed by the power supply voltage, and it’s rate of flow is limited by the components.
Never connect the power supply terminals directly to each other (short circuit) with metal or other low resistance material.
You can’t see electric current, you can only detect it’s effects. So, it helps to visualize it in a way similar to what is drawn below.
- Mechanical switches are made so that they don’t conduct current while they are open/off (no metal on metal contact), but when closed/on (metal on metal contact), they conduct freely.
- Resistors provide a specific resistance to a circuit. They come in a lot of values. When the same voltage is applied, lower value resistors conduct more current than higher value resistors do. Lower values resistors also produce more heat with the same voltage across them as a higher value resistor due to the higher current. Preventing too much heat in any circuit is always the top priority in electronics!
Reminder: Power (heat production for resistors) is the voltage across a component, times the current through the components. P = VI
Push button switches on a breadboard:
- Common push button switches usually fit into breadboards reasonable well. A new breadboard will likely pop out push button switches once in a while.
- The 2 pins at the top of the push button switch connect together the 2 breadboard rows that they plug into.
- Bottom 2 pins of the pushbutton switch also connect together the 2 breadboard rows that they are connected into.
- Pressing the switch button until it clicks, to turn it on, connects the top 2 rows to the bottom 2 rows electrically (Illustrated in the diagram above). This is known as a normally off/open (NO) switch. There is also normally on/closed (NC) switches. I have not come across any NC pushbutton switches, only seen
- High side switching is when the switch is on the more positive side of the circuit than the load. That’s the most common position for the switch.
- Low side switching is when the switch is on the more negative side of the circuit than the load. That is the less common position, but still an OK place to put the switch if it is better for the circuit. Some people will be annoyed that you put it there though. Plus, some transistors (NPN BJTs) have to be on the low side when wired as a switch.
Current only flows through a diode (such as an LED), when the anode is more positive than the cathode. The 3 horizontal lines next to the LED (light emitting diode) cathode in the drawing above is the schematic symbol for 0 volt reference point ground. Usually just referred to as ground, which is usually located at the negative side of a battery when using a battery.
9V+ (or +9V) is being used to represent the positive terminal of a 9V battery. There’s a 9V difference between +9V and ground (0V).
Breadboard power supply basics:
Affiliate link ad. I recommend getting multiple breadboard power supplies if you plan to use them. They can be damaged easily, but don’t cost very much. There’s a link to the AC to DC adapter I bought a little bit further down the page. The breadboard power supply usually doesn’t come with an AC to DV adapter, even when it is part of a larger kit.
Breadboard power supplies have pins that plug into the breadboard supply rails. The supply has to be powered at the barrel jack, typically with a 9V AC to DC wall adapter.
Breadboards are used to quickly build, modify and study test circuits. Breadboards have a lot of slots for wires to be inserted into. Each row of slots is connected together electrically within the board. On both sides of the board, there are a bunch of rows of 5 slots across that are connected to each other. There’s a groove down the middle that separates the 2 sides of 5 slot rows.
Then there’s 2 rows of slots connected from top to bottom on both sides, which is intended for connecting the power supply to. Some boards don’t connect all the way from top to bottom along the sides, but I have never gotten one like that.
Adjustable AC to DC adapter I really like. An affiliate link ad.
I really like the kit above for a single purchase to learn basic electronics and Arduino. This is an affiliate link ad, so I earn from qualifying purchases, which helps me devote time to improving this site.
Physical appearance of commonly used through hole (wires sticking out) components:
Common Schematic symbols for components:
Schematic diagrams are drawings of circuits where symbols are used to identify components and their connections.
Low voltage incandescent light bulb circuit:
An incandescent light bulb can be connected directly to a power source as long as it is rated to handle the amount of voltage that is applied. They have a resistive filament that gets hot enough to emit light when a voltage forces enough current through it.
In the United Sates, incandescent light bulbs wired directly to household electricity are rated for 120V alternating current (AC). That’s the voltage of most outlets.
Other types of light bulbs are also made to plug directly into a house’s light sockets due to protection circuitry built into them.
LED with protective resistor circuit:
LEDs (Light Emitting Diodes) have mostly replaced incandescent light bulbs these days.
The 3-5mm indicator LED is commonly used to learn electronics circuits.
LEDs must be inserted in the proper direction (forward biased) in order to light up. They also must be protected from too much current. Usually a series resistor is used to protect the LED.
Affiliate link ad.
- LED must be inserted in the right direction to light up (forward biased). That is when the Anode (longer lead) is more positive, and the Cathode (shorter lead) is more negative, assuming that the Anode lead has not been trimmed. Leads (pronounced as “leeds”) are the metal wires coming out of any through hole component. The leads are what go through the holes of a circuit board, and then are soldered on the other side. Many LEDs also have a flat edge on the cathode side.
- Rectifier diodes are what are used when you actually want to prevent current from flowing in the wrong direction. They conduct more easily (lower forward voltage) and can handle more current than LEDs. They also have a much higher reverse breakdown voltage than LEDs, which means that they can block a lot more voltage while reverse biased.
Rectifier and other types of diodes have a band painted on the cathode side of the component.
Minimum resistance to protect an LED from common low voltages
Until you are comfortable with calculating circuit current and resistor wattage, here are some good minimum value resistors to use to protect an LED from a given voltage. This assumes that you are using 1/4W (quarter watt) resistors, which are by far the most commonly available wattage value.
- 5V – 220Ω (two hundred twenty ohms)
- 9V – 470Ω (four hundred seventy ohms)
- 12V – 1000Ω (1k) (one thousand ohms/one kilohms)
Notice how I suggest to use about 4 times the resistance to protect an LED from a little more than twice the voltage when comparing a 5V supply with a 12V power supply. Resistors get 4 times as hot when the voltage across them doubles. 2 times the voltage and 2 times the current = 4X the wattage.
The relationship between voltage and current of a resistive component is known as Ohms law. The 3 main formulas for doing Ohms law calculations are
- I = V/R
- R= V/I
- V = IR
- 5V/220Ω = 0.022727…A (which is rounded off to 23mA)
- 12V/1000Ω (same as 1k) = 0.012A (same as 12mA)
Current through a resistor and a series LED that drops 2V:
- 3V/220 = 0.013636… (14mA)
- 10V/1,000Ω = 0.01A (10mA)
Protective resistor must have high enough resistance to limit current below 20mA for most indicator LEDs. At higher voltages, current will need to stay well below 0.02A (20mA) to prevent the resistor from overheating.
Most resistors are rated to dissipate a maximum of 1/4W (0.25W) of power. However, it is still recommended to stay below 1/8W (0.125W). Other wattage resistors are fairly easy to find. They should also be kept below half of whatever their maximum wattage rating is.
To calculate wattage, take the voltage (in volts) across a components, and multiply it by the current through it (in amps). W = V x I
Batteries are a cheaper and more portable voltage source than a plug in power supply, but they need to either be replaced often, or recharged if rechargeable.
A cell contains the chemistry needed to provide a voltage. The nominal voltage will depend on the chemistry involved.
Nominal voltage is close to the average voltage that you can expect when a cell goes from fully charged (highest voltage possible) to fully discharged (lowest practical voltage).
- Alkaline has a nominal cell voltage of 1.5V. The actual voltage ends up being about 1.6V while brand new (they aren’t usually rechargeable), and somewhere close to 1V when fully discharged.
- Lithium ion (li ion) cells usually have a nominal voltage of 3.6V, which ends up being 4.2V when fully charged and 3V when fully discharged. Always stay within that voltage range and below it’s maximum current to prevent damage.
- Series cells: Cells must be at the same voltage and capacity (mAh) Connecting cells end to end (positive of one cell to negative of another cell) adds up the voltage of each cell when measured from the 2 far ends.
- Parallel cells: Cells must be at the same voltage when connected. Connecting the positive side of a number of cells together while also attaching their negative side together adds up how much total current can be provided to a load. Make sure the batteries are at the same voltage (no more than about 0.1V difference) before connecting in parallel.
Battery holders, which connect the cells in series or parallel for you when you insert them in the proper direction, are common.
A 9V alkaline battery has the chemistry of six 1.5V cells connected in series contained in one package.
BEWARE that a”9 volt” lithium ion rechargeable batteries can only be charged to 8.4V. That is because they are made up of two series 3.6V cells (4.2V cells when fully charged). I prefer to call them almost 9V batteries. 4.2V + 4.2V = 8.4V
Always use a proper battery charger for the chemistry involved, unless you have learned how to charge that chemistry safely.
Really nice looking resistor kit for those beginning studying electronics. Affiliate link ad.
Nice assortments of semiconductors. Amazon affiliate link ad.
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