Voltage sources, and the accompanying current that they provide, are needed for all electronic circuits. This page only covers direct current (DC) voltage sources which have 2 terminals. One terminal for positive (usually red) and one terminal for negative (usually black). Negative terminal is declared as being the 0V reference point ground while the positive terminal is considered to be the supply voltage in relationship to ground.
- Battery – Voltage is the result of a potential of chemical reactions. Once a conductive enough path is connected, the chemical reactions take place as needed to move current. Forcing current into rechargeable batteries reverses the chemical changes and recharges the battery. Voltage goes down while discharging, and if rechargeable, goes up while recharging. You must always stay within the limits of any particular battery chemistry, so make sure to investigate them. Some common battery types are lithium ion, alkaline and Lead acid.
- DC power supply – Takes the voltage and current from an outlet, or battery, and converts it into a usable voltage, often with the capability to limit current (by dropping voltage if need be). Voltage and maximum current may be fixed or adjustable.
There are a lot of voltage sources to choose from, so you need to research the specifics of whatever particular one(s) you are interested in.
I talk about using DC power supplies and lots of other topics in this video. Electronics course 1 Resistor component limiting current Ohms law and multimeter measurements
- Ideal voltage source: Impossible to achieve, but it would be a voltage source that can hold a steady voltage no matter how much current is demanded. The less internal resistance a voltage source has, the closer it comes to being an ideal voltage source.
- Split/dual power supply: Sometimes you need both a positive and a negative voltage in relationship to ground (0V reference point). If you don’t want to buy a dual power supply then you can tap into the middle of series batteries and assign that point as the 0V reference point. Plus, here’s some other options.
- Brief TLE 2426 three terminal rail splitter virtual ground component introduction
- Brief op amp rail splitter circuit turning single into split dual supply
Obtaining a different voltage/power from fixed voltage supplies.
- Series batteries: Connecting batteries in series adds up their voltage. It is important to use batteries with the same voltage and capacity, and to make sure their voltages stay balanced.
- Parallel batteries: Splits up the current demands, and thus can provide more current and total charge than a single battery. They absolutely must have about the same voltage when connected together, or high current will flow from the higher voltage battery to the lower voltage battery. After being connected together, they will automatically keep their voltages equal.
- Non adjustable power supplies will need either a voltage buck and/or boost converter ,or a voltage regulator to get a different voltage.
Buck converters takes in a higher voltage/lower current and outputs a lower voltage/higher current.
Boost converters takes in a lower voltage/higher current and outputs a higher voltage/lower current.
There will be at least a little loss of power (voltage times current) though because no converter is 100% efficient.
Voltage regulators also output a lower voltage than the supply voltage. They don’t convert current and voltage, but instead they just basically add resistance as needed to set a voltage across the rest of the circuit. They get very hot, but they are very convenient when you just need low power for a lower voltage part of a circuit.
Not finding my voltage boosters, so here’s an affiliate link ad to some that are lower priced and have good reviews.
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Other basic electronics topics that you should know before moving on to more advanced topics.
- Electronic component appearance and schematics – Commonly used through hole versions
- Electronic circuit basics
- Voltage sources for electronics basics
- Multimeter measuring voltage
- Resistor component – Learning electronics resistors
- Light Emitting Diodes – Indicator LEDs
- LED circuit -Lighting a Light Emitting Diode
- Resistor limiting current – Ohms law
- Multimeter measuring current
- Wattage – Electrical Power unit
- Resistors connected in parallel
- Series resistors
- Voltage divider – Setting a fractional voltage
- Resistor color code
- Diode – Rectifier
- Trimpot – Trimmer potentiometer – Voltage divider – Variable resistor
- Capacitor component
- Capacitor RC time constant
- Voltage ramp Demonstrated using a capacitor.
- LM334 three terminal adjustable current source not a common component. I use for an easy current source in many circuits.
- Switch NOT logic gate – digital signal inverter
- Switch OR gate – LED circuit
- Switch AND gate – LED circuit
- Switch based NAND logic gate – LED demonstration circuit
555 timer is an integrated circuit (IC). Being an IC, it has complex circuitry combined in a single package with external pins/terminals to connect to other circuitry. You can easily make all kinds of fun circuits with just a 555 timer and the components covered above, so I think it’s a good component to learn next.
- 555 Timer IC This particulars of this integrated circuit covered on this page make a lot more sense after you study the basic circuits that follow.
- 555 timer bistable mode – Flip flip basic circuit
- 555 timer monostable mode – One shot
- 555 timer astable multivibrator mode – Flashing LEDs
- 555 timer schmitt trigger logic inverter – NOT gate
- 555 timer LDR controlled astable multivibrator mode LED flasher circuit
- 555 timer – Buzzer output – Astable multivibrator mode – Light dependent resistor LDR controlled circuit
Transistors will probably be the most challenging components to learn. Understanding them will help you understand all of electronics much better, and help you the most in being creative while designing your own circuits.
- NPN BJT switch circuit – Bipolar Junction Transistor – 2N3904
- PNP BJT switch – Bipolar Junction Transistor – 2N3906
- NPN BJT emitter follower circuit – transferring a voltage minus a diode drop
- PNP BJT emitter follower circuit – Transferring weak signal voltage with a diode voltage shift
- Bipolar Junction Transistor BJT voltage follower circuit improved to eliminate base emitter diode shift
- NPN BJT current source – Bipolar Junction Transistor – 2N3904
- PNP BJT current source – Bipolar Junction Transistor – 2N3906
- Schmitt trigger – NPN BJT
- Zener diode component – voltage reference – regulator
- Voltage doubler circuit fragment- Capacitor charge pump – Some V loss
- 7805 5V positive voltage regulator IC
- Battery voltage state of charge SOC – From fully charged to discharged
These pages are still being compiled.
Circuits covered more quickly series:
- Brief polarity indicator LEDs circuit
- Brief capacitor charge and discharge through LEDs circuit
- Brief capacitor charging RC time constant demonstration circuit
- Brief 555 bistable mode flip flop alternating LEDs circuit