What Is a Parallel Circuit? Much more common than series circuits are those wired in parallel—including most household branch circuits powering light fixtures, outlets, and appliances. A parallel circuit is also a closed circuit where the current divides into two or more paths before coming back together to complete the full circuit. Parallel-in to Serial-out (PISO) Shift Register. The Parallel-in to Serial-out shift register acts in the opposite way to the serial-in to parallel-out one above. The data is loaded into the register in a parallel format in which all the data bits enter their inputs simultaneously, to the parallel input pins P A to P D of the register. Key Differences between Series and Parallel Circuits. In electrical and electronics engineering it is very important to know the differences between series and parallel circuits. They are the two most basic forms of electrical circuit and the other one being the series-parallel circuit, which is the combination of both, can be understood by applying the same rules. One would choose to connect his batteries in parallel when he needs higher capacity; the battery bank has same voltage as the batteries its consists from, but its capacity is the sum of the batteries capacity. Supposing you need 12 V but 104 Ah, you could connect two 12 V 52 Ah batteries in parallel. Series-Parallel Connection. Explanation of series and parallel circuits and the differences between each. Also references Ohm's Law and the calculation of total resistance in each type.
More often than not a question pops up in our forum about speaker impedance and the result of connecting multiple speakers to a single amplifier. Thus we have prepared this introductory tutorial to help clear up some of these questions.
The most common ways of hooking up more than one speaker to an amplifier channel are:
- Series Connection
- Parallel Connection
- Series-Parallel Connection (for more than 2 speakers)
There are pros and cons to each method which we will discuss herein.
To understand the differences, we must first explore the very basic principle of how electricity flows through a circuit.
Ohms Law: V = i * R where V = voltage, i = current, R = resistance (1)
A loudspeaker isn't a simple resistance because it is an electroacoustical-mechanical device which is usually governed by a complex passive crossover network comprised of inductors, capacitors and resistors. Thus the speaker system presents a complex impedance which varies with frequency and power level. 'Complex' here means impedance is a vector quantity possessing both phase & magnitude.For simplicity sake, we shall model our system's impedance magnitude only, ignoring phase . As an example, let's look at an impedance curve (or modulus of impedance) of an actual loudspeaker (the Onix x-ls).
Graph 1: Sample system modulus of impedance
The impedance minimum 0f 6.56 Ω at 42 Hz indicates the vented box tuning frequency. There are two other local minima, found at 164 Hz (6.386 Ω) and 3.4 kHz (4.97 Ω). That the first two minima are proximal in magnitude indicates an efficient reflex action. The large impedance peak, found at ~ 850 Hz arises as a result the interaction of the crossover network's high- and lowpass sections, setting up a parallel resonance. The impedance phase swings between +39° and -54° across the audible spectrum. With a lowest magnitude minima value of 4.97 Ω, the system nominal impedance (per IEC standards) value would be 6 Ω.
Series Connections Basics
Schematic 1: Series Circuit
As you can see in our diagram above, we have connected Zspk1 and Zspk2 in series with our amplifier (Vs). Using Ohms law (1) we can calculate the following relationships:
Equivalent Impedance also known as the Thevenin Impedance where we short our voltage source (in this case our amplifier) to calculate the total load it will see from our two speakers connected in series.
Zeq = Zspk1 + Zspk2 (2)
For simplicity, we shall use identical speaker loads from the speaker we showed in the above example.
Hence, Zspk1 = Zspk2
Zeq = 6 + 6 = 12 ohms
Thus by connecting two speakers in series, the amplifier now sees double the load impedance. But how does this translate to power delivery?
In a series circuit, there is only one path from the source through all of the loads and back to the source. This means that all of the current in the circuit must flow through all of the loads and the current though each load is the same.
To calculate voltage drop through each load, we apply Ohms law: (1)
Vspk1 = i * Zspk1
Vspk2 = i * Zspk2
Next we apply Kirchoff's Voltage Law (KVL) which dictates the sum of the voltages within a circuit must equate to zero.
Thus we get the following relationship:
Vs = Vspk1 + Vspk2 or Vspk1 + Vspk2 - Vs= 0
Let's assign some arbitrary numbers to solve for the variables in our equations.
Vs = 10V
Zspk1 = Zspk2 = 6 ohms (as per our speaker example)
First we must solve for current in the circuit so we can calculate our voltage drops to each load.
Using KVL we write the following mesh equation:
-10V + i*(6) + i*(6) = 0
Solving for I, we get: i = 10 / 12 = 0.83A
Now we can solve for our load voltages using Ohms law (1):
Vspk1 = i * Zspk1 = 0.83A * 6 ohms = 5V
Vspk2 = i * Zspk2 = 0.83A * 6 ohms = 5V
Of course a more simplified method known as the Voltage Divider principle can be used for calculating voltage across loads in series circuits. Here is how we can quickly solve for Vspk2:
Voltage Divider Relationship: Vspk2 = Vs * (Zspk2) / (Zspk1 + Zspk2) (3)
Using KVL we check to see if the sum of our load voltages equal our source so that the total voltage summation in the circuit equates to zero.
-Vs + Vspk1 + Vspk2 = 0
-10 + 5 + 5 = 0
as you can see we correctly calculated our circuit voltages as KVL was satisfied. Working up a circuit model using Electronics Workbench (EWB) confirms this.
Schematic 2: Series Circuit
But what about power?
To calculate our power to each loudspeaker, we must first develop a relationship for power.
Here are three commonly used equations: P = V * i ; P = V^2 / R or P = i^2 * R (4)
The Handy Dandy Ohms Law Pie Chart
Since we calculated all of our circuit voltages and current, we can find power with either of the above equations. Let's use P = V^2 / R only we shall represent R as Z for our loudspeaker magnitude.
Pspk1 = Vspk1^2 / Zspk1 = (5V)^2 / 6 = 25 / 6 = 4.17 watts
Pspk2 = Vspk2^2 / Zspk2 = (5V)^2 / 6 = 25 / 6 = 4.17 watts
Ptot = Pspk1 + Pspk2 = 4.17 watts + 4.17 watts = 8.33 watts
If we were to rework this example for just one 6 ohm loudspeaker connected to our amplifier, we would have seen the following power delivery to the loudspeaker:
Pspk = 10^2 / 6 = 16.67 watts since all of the voltage from our amplifier would have been delivered to the single loudspeaker load. Once again our model confirms this.
Schematic 3: Single Load
Thus connecting two speakers in series resulted in ½ the power consumption of just one speaker directly connected to our amplifier. This makes sense since the amplifier is now seeing double the load impedance and delivering only ½ the current.
So how does this equate to sound pressure levels?
Since we connected two identical speakers in series with our amplifier, each speaker only sees half the voltage drop across it thus as a result will see only 1/4 the power delivered to each speaker compared to a single speaker connected to our amplifier. The equivalent SPL now produced by each speaker is 6dB lower than if a single speaker were playing off the amplifier, for a combined overall -3dB drop. However, running two speakers effectively doubles the volume displacement compared with that of one speaker. Thus playback through the two drivers results in a 3dB gain. Adding this to the 3dB drop previously mentioned and the net overall sound pressure level will remain unchanged. Thus, playing two identical speakers connected in series off of a common amp (as opposed to playing just one speaker off that amplifier) results in no level drop, when compared to the single speaker case. This analysis, of course, ignores mutual coupling and any room-induced acoustical artifacts. However, if the speakers connected in series are not co-located and summing perfectly in the room, the net SPL would likely be up to -3dB lower than playing a single speaker off the same amplifier. The net SPL product in this case has a dependent relationship on distance between the speakers and frequencies they are destructively interfering in the room.
Modeling both a single-driver system as well as a series-wired, dual-driver system we see the dB spl plots are virtually identical.
Graph 2a: Single driver, system model: Amplitude response. dB spl @1m/2.828Vac drive level, ref. to 20 μPa.
Graph 2b: Dual- driver, series wired system model: Amplitude response. dB spl 1m/2.828Vac drive level, ref. to 20 μPa.
Introduction
This section will go into more depth on series, parallel and series-parallel connections. The purpose of this section is to explain why certain connections are utilized, how to set up to your desired connection, as well as going over what is the most beneficial connection to utilize based on your situation.
Why parallel?
Strictly parallel connections are mostly utilized in smaller, more basic systems, and usually with PWM Controllers, although they are exceptions. Connecting your panels in parallel will increase the amps and keep the voltage the same. This is often used in 12V systems with multiple panels as wiring 12V panels in parallel allows you to keep your charging capabilities 12V.
The downside to parallel systems is that high amperage is difficult to travel long distances without using very thick wires. Systems as high as 1000 Watts might end up outputting over 50 amps which is very difficult to transfer, especially in the systems were your panels are more than 10 feet from your controller, in which case you would have to go to 4 AWG or thicker which can be expensive in long run. Also, paralleling systems require extra equipment such as branch connectors or combiner box.
Why series?
Strictly series connections are mostly utilized in smaller systems with a MPPT Controller. Connecting your panels in series will increase the voltage level and keep the amperage the same. The reason why series connections are utilized with MPPT controllers is that MPPT Controllers actually are able to accept a higher voltage input, and still be able to charge your 12V or more batteries. Renogy MPPT Controllers can accept 100 Volts input. The benefit of series is that it is easy to transfer over long distances. For example you can have 4 Renogy 100 Watt panels in series, run it 100 feet and only use a thin 14 gauge wire.
Serial Port
The downside to series systems is shading problems. When panels are wired in series, they all in a sense depend on each other. If one panel is shaded it will affect the whole string. This will not happen in a parallel connection.
Why series-parallel?
Solar Panel arrays are usually limited by one factor, the charge controller. Charge controllers are only designed to accept a certain amount of amperage and voltage. Often times for larger systems, in order to stay within those parameters of amperage and voltage, we have to be creative and utilize a series parallel connection. For this connection, a string is created by 2 or more panels in series. Then, an equal string needs to be created and paralleled. 4 panels in series needs to be parallel with another 4 panels in series or there will be some serious power loss. You can see more in the example below.
What Is Serial Communication And How It Works? [Explained]
There isn’t really a downside to series-parallel connections. They are usually used when needed and other options are not available.
![What is Serial Communication and How it works? [Explained]](https://cdn10.bigcommerce.com/s-fhnch/product_images/uploaded_images/image004.png?t=1464170501 "What is Serial Communication and How it works? [Explained]")
How to set up your system in parallel.
A Parallel connection is accomplished by joining the positives of two panels together, as well as the negatives of each panel together. This can be accomplished by different means, but usually for smaller systems this will be utilized via branch connector. The branch connector has a Y shape, and one has two inputs for positive, which changes to one, along with two inputs for negative, which changes for one. Please see picture below.
Model 2.4.1
As you can see you have a slot for the negative terminal of panel #1 and the negative terminal of panel #2. As well as the positive equivalents. Then the negative out and the positive out will be utilized to connect to your charge controller via a solar PV cable.
Please see diagram below.
Model 2.4.2
Let’s look at a numerical example. Say you have 2 x 100 Watt solar panels and a 12V battery bank. Since each panel is 12V and the battery bank you want to charge is 12V, then you need to parallel your system to keep the voltage the same. The operating voltage is 18.9V and the operating current is 5.29 amps. Paralleling the system would keep the voltage the same and increase the amps by the number of panels paralleled. In this case you have 5.29 Amps x 2 = 10.58 Amps. Voltage stays at 18.9 Volts. To check math you can do 10.58 amps x 18.9 volts = 199.96 Watts, or pretty much 200 Watts.
How to set up your system in series
A Series connection is accomplished by joining the positive of one panel to the negative of the other panel together. With this you do not need any additional equipment except for the panel leads provided. Please see diagram below.
Tajima Serial Connection Vs Parallel Connection
Model 2.4.3
Let’s look at a numerical example. Say you have 2 x 100 Watt solar panels and a 24V battery bank. Since each panel is 12V and the battery bank you want to charge is 24V, then you need to series your system to increase the voltage. For safety, use the open circuit voltage to calculate series connections, in this case the 100 Watt panel has 22.5 Volts open circuit, and 5.29 amps. Connection in series would be 22.5 volts x 2 = 45 volts. Amps would stay at 5.29. The reason we use open circuit voltage is we have to account for the maximum input voltage of the charge controller.
*If you want to check math it won’t work with the open circuit voltage. You can use the operating voltage, so 18.9 volts x 2 = 37.8 volts. 37.8 volts x 5.29 amps = 199.96 Watts, or pretty much 200 Watts.
How to set up your system in series-parallel
A series-parallel connection is accomplished by using both a series and a parallel connection. Every time you group panels together in series, whether is 2, 4, 10, 100, etc. this is called a string. When doing a series-parallel connection, you are essentially paralleling 2 or more equal strings together.
Please see diagram below
Model 2.4.4
As you can see this series parallel connection has 2 strings of 4 panels. The strings are paralleled together.
Tajima Serial Connection Vs Parallel Circuits
Let’s look at a numerical example for this diagram. This is mostly used on our Renogy 40 Amp MPPT Controller as it can accept up to 800 Watts of power, but only can accept 100 Volts in, which is why you cannot do everything in series. Paralleling 8 panels as well would cause too high of an amperage.
For this example, you would use the open circuit voltage of 22.5 Volts and the operating current of 5.29 Amps. Creating a string of 4 panels, you will have a voltage of 22.5 Volts x 4 = 90 volts, which is under the 100 Volt limit. Then by paralleling on the other string, the voltage will stay 90 volts and the amps will double, so 5.29 amps x 2 = 10.58 Amps.
* Keep in mind there is usually another factor that needs to be taken into account when sizing for the MPPT Controller called the boost current. This will be discussed in the charge controller section.
*If you want to check math it won’t work with the open circuit voltage. You can use the operating voltage, so 18.9 volts x 4 = 75.6 volts. 75.6 Volts x 10.58 amps = 799.85 Watts, or pretty much 800 Watts.