Learning basic electronics for beginners is the primary goal of this site.
I still have a lot of updating to do on this and my other pages. Please check back soon and forgive any mistake and sloppiness as I shuffle things around!
- Power supply provides voltage and current.
- Load usually does something useful (emit light, turn a motor, creates sound, etc.) with voltage and current (power). Plus the load always creates waste heat with some to all of the power applied to it.
- Conductors let voltage and current 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.
Bench power supplies plug into the wall’s higher alternating current (AC) voltage, and output a lower direct current (DC) voltage. They also usually have a maximum current limit that you can set it to. They aren’t as cheap short term, or as portable as a 9V battery (and battery snap) or breadboard power supply (which also needs 9V wall adapter with 5.5 x 2.1mm barrel plug) that I use in many of my drawings.
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Basic electronics introduction:
You need to be familiar with basic circuits before you will be able to understand more complex circuits.
This is a drawing of an LED (Light Emitting Diode) with a 470 ohm current limiting resistor which protects all components of the circuit from overheating. They are powered by a 9V battery, all connected together on a prototype breadboard.
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. There’s 5 connected slots across each of the two middle rows, there’s a groove down the middle where they are not connected. 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.
Primary goals when building/designing a circuit:
Whenever studying a new circuit, make sure you understand how every part of the circuit contributes to these 2 goals.
- Don’t let any part of the circuit overheat.
- Use components that provide the desired outcome.
Visualizing electric current:
Current/electrons runs through all series (connected end to end) components and power supply equally. It is pushed by the power supply voltage and it’s rate of flow is limited by the components. It has enough similarities to water flowing through pipes being pushed by a pump, that it helps to visualize current in that way.
Current/electrons only flows through a diode (such as an LED) when the anode is more positive than the cathode. The 3 lines next to the LED (light emitting diode) cathode in the drawing above is the schematic symbol for 0V reference point ground. That typically represents the negative side of a battery, while 9V+ is being used to represent the positive of a 9V battery. There’s a 9V difference between those 2 points.
Breadboard power supply basics:
Affiliate link ad. Breadboard power supplies can be damaged relatively easily. I suggest getting a number of them if you want to use them. 5 should be good to start off with. There’s a link to an AC to DC adapter a little bit further down the page. The breadboard power supply doesn’t usually come with an AC to DV adapter, even when it is part of a larger kit.
Breadboard power supplies that have pins that plug into the breadboard supply rails. The supply has to be powered at the barrel jack, typically with a AC to DC wall adapter.
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.
Electronics involves the study of electric circuits.
A simple circuit needs at least a power supply and a load (one or more components that can safely handle the voltage of the power supply).
Sometimes you will see a block diagram of an entire circuit or of how a number of individual circuits are connected together. Block diagrams are are usually very vague because they usually simply represent the basic connections of a lot of possible circuits.
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, instead of using drawings or pictures of actual components.
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 that much voltage. They have a resistive filament that gets hot enough to emit light when a voltage forces enough current through it. They dim as the amount of current goes down (due to less voltage).
Schematic symbols are almost always used to represent actual components in electrical circuit drawings called schematic diagrams.
Incandescent light bulbs that are used in housing are rated for 120V alternating current (AC) in the US.
LED with protective resistor circuit:
LEDs (light emitting diodes) have almost completely replaced light bulbs these days. They 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.
- Forward biased diode is when the Anode (longer lead if untrimmed) is more positive than the cathode (shorter lead if untrimmed).
Most LEDs need to have current limited to below 20mA (20 milliamps). That is the same as 0.02A.
Most resistors are rated for 0.25W, but should be kept below 0.125W. Power in watts, is the voltage in volts, times the current in amps.
- A red LED usually drops about 2V from the protective resistor. Blue or green LEDs usually drop about 3V. The voltage across the resistor in this circuit is the supply voltage minus the voltage drop of the LED. The resistor the sets the current through all series components based on the voltage across it.
- 12 volt circuit: 10V/1,000Ω = 0.01A (circuit current) … 0.01A x 10V = 0.1W (resistor heat generated) … The red LED is less bright (10mA) in the 12V circuit than the 9V circuit (15mA) in the drawing above.
- 9V circuit: 7V/470Ω = about 0.015A …. 0.015A x 7V = 0.105W … The 9V circuit LED is more bright and it’s resistor is not getting noticeably hotter than the 12V circuit in the drawing above.
Those topics are covered in more detail below.
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. That assumes that the Anode lead has not been trimmed. Leads (pronounced as “leeds”) are the metal wires coming out of through hole components. 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) when forward biased than LEDs, and they have a much higher breakdown voltage. That means that they can block a lot more voltage while reverse biased, without being destroyed. than an LED can.
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 resistor wattage, here are some good minimum value resistors to use to protect an LED from a given voltage. This assumes you are using 1/4W (quarter watt) resistors, which are by far the most common wattage value used.
- 5V – 220Ω (two hundred twenty ohms)
- 9V – 470Ω (four hundred seventy ohms)
- 12V – 1000Ω (1k) (one thousand ohms/one kilohms)
Notice how I put over 4 times the resistance to protect an LED from a little more than twice the voltage. Resistors get a lot hotter as voltage rises, and therefore current needs to be limited more to prevent the resistor from overheating.
A couple current through just a resistor calculations:
- 5V/220Ω = 0.022727…A (which is 23mA rounded off)
- 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. 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. However, 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 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 it’s maximum current to prevent dangerous 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 end of each cell to the positive of the others, as well as connecting the negatives ends together, provides the same voltage as one cell, but 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 that 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 contained in one package.
“9 volt” lithium ion rechargeable batteries can only be charged to 8.4V because they are made up of two 3.6V cells (4.2V cells when fully charged). I prefer to call them almost 9V batteries.
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.
- Information on this site is not guaranteed to be accurate. Always consult the manufacturer info/datasheet of parts you use. Research the proper safety precautions for everything you do.
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