# HOW TO KNOW WHATS IN PARALLEL OR SERIES

#### JefferyJames

Joined May 3, 2020
8

BATTERIES ARE FOR VISUAL.
Hey I've got this circuit and i need to know whats in parallel or in series so i can draw it out to pick suitable batteries.
How do i know whats in series or parallel?

#### Papabravo

Joined Feb 24, 2006
14,831
Everything is in parallel, unless it is not.

#### JefferyJames

Joined May 3, 2020
8
Everything is in parallel, unless it is not.
Papabravo, what do you mean by 'unless it is not'.

#### Papabravo

Joined Feb 24, 2006
14,831
Papabravo, what do you mean by 'unless it is not'.
With respect to a power source, if it is connected to that power source it is in parallel.
Things that are not connected to that source are not in parallel with that source.
Seems pretty simple, what have you read? Do you have different information?

#### SamR

Joined Mar 19, 2019
2,895
If a device is in Parallel it is attached to the parallel device by 2 points instead of one. And Welcome to AAC!

#### MrChips

Joined Oct 2, 2009
22,474
If two things are in parallel they experience the same voltage.
If two things are in series they conduct the same current.

#### SamR

Joined Mar 19, 2019
2,895
Corrected:

Last edited:

#### JefferyJames

Joined May 3, 2020
8
If a device is in Parallel it is attached to the parallel device by 2 points instead of one. And Welcome to AAC!
With respect to a power source, if it is connected to that power source it is in parallel.
Things that are not connected to that source are not in parallel with that source.
Seems pretty simple, what have you read? Do you have different information?
Always have a rough time getting my head around this all. So your saying that my motor shield, and two motors are all in parallel, my controller, magnetometer, HC-SR04, LED and servo are in parallel, but how do they connect up as the motor shield is connected to the controller?

#### SamR

Joined Mar 19, 2019
2,895
Arduino does not have the ampacity to drive motors hence the motor control shield which should have a separate source of motor power and not powered from the Arduino 5V pin. Another common way to power motors with Arduino is a switching transistor with a separate and higher voltage supply. In that case, you also want to use an optic isolator in the circuit to protect the Arduino from the higher voltage supply for the motor. Lots of things to consider when using Arduino with motors.

#### Papabravo

Joined Feb 24, 2006
14,831
Always have a rough time getting my head around this all. So your saying that my motor shield, and two motors are all in parallel, my controller, magnetometer, HC-SR04, LED and servo are in parallel, but how do they connect up as the motor shield is connected to the controller?
Maybe you should learn to crawl and walk before trying to run a marathon. Things which do not share a common power source can still talk to each other if they have a common ground, and the voltage drop along the common ground is not too large. Separate power supplies for control and motor power are common. Here you want to make sure that motor power ground and digital ground and analog ground are connected at a single point, so noise from one sources does not couple into the others.

#### JefferyJames

Joined May 3, 2020
8
Maybe you should learn to crawl and walk before trying to run a marathon. Things which do not share a common power source can still talk to each other if they have a common ground, and the voltage drop along the common ground is not too large. Separate power supplies for control and motor power are common. Here you want to make sure that motor power ground and digital ground and analog ground are connected at a single point, so noise from one sources does not couple into the others.
Arduino does not have the ampacity to drive motors hence the motor control shield which should have a separate source of motor power and not powered from the Arduino 5V pin. Another common way to power motors with Arduino is a switching transistor with a separate and higher voltage supply. In that case, you also want to use an optic isolator in the circuit to protect the Arduino from the higher voltage supply for the motor. Lots of things to consider when using Arduino with motors.
Not too experienced I know...
Still confused, if everything is in parallel, every component will get the same amount of voltage from the battery. Say if I had say 6V battery, would everything plugged into the 5V pin run off 6V or 5V?.

#### JefferyJames

Joined May 3, 2020
8
Arduino does not have the ampacity to drive motors hence the motor control shield which should have a separate source of motor power and not powered from the Arduino 5V pin. Another common way to power motors with Arduino is a switching transistor with a separate and higher voltage supply. In that case, you also want to use an optic isolator in the circuit to protect the Arduino from the higher voltage supply for the motor. Lots of things to consider when using Arduino with motors.
When you say the motor off the 5V pin are you referring to the servo? I've read that the maximum current provided by the 5V controller pin is 1A which is enough for my servo.

#### SamR

Joined Mar 19, 2019
2,895
NO Each pin has a max limit of 40mA and all pins together, a max total of 200mA. I can run a hobby servo alone on an Arduino including its control but you have quite a bit loaded onto that Arduino with the shield. Which is why motors need a separate power source. The shield requires a separate power source for motor power. The shield motor control is powered by the Arduino but not the motor itself.

if everything is in parallel, every component will get the same amount of voltage from the battery.
What is in parallel? And NO, the battery supplies power to the Arduino which has a voltage regulator to supply both 3.3V and 5V to the respective power pins and to operate the Arduino. Still a 40mA max on each I/O pin. The 5V output pin is good for ~400 mA on USB, ~900 mA when using an external power adapter The 900 mA is for an adapter that provides ~7V. Subtract the I/O load from that total and you are left with, once again, ~200mA+ on the 5V power pin depending on the power supply capacity. And when using a fresh new 9V battery to power the Arduino it may originally supply near 1A but goes down fast if any real load on the Arduino. Which is why I typically run my Arduinos off of USB or a Wall Wart power supply and not batteries. The Arduino uses power for many things just to operate, with nothing even attached to it but the power supply. This is why some people simply use a single programmed chip such as the ATtiny without all the peripherals.

#### WBahn

Joined Mar 31, 2012
26,398
The first image is not of two devices in series. To be in series requires that what ever current flows in one of them must then flow in the other. In that instance, you are guaranteed that this cannot happen as the current must split with some of it going through one and the rest going through the other (and no part of it going through both). They may or may not be in parallel as we don't know what happens to the dangling wires at the bottom. To be in parallel requires that whatever voltage appears across one of them must be the same voltage that appears across the other. So if you connect the two wires together they will be in parallel (and you then just have the same situation as in the right-most image).

#### SamR

Joined Mar 19, 2019
2,895
Yeah, was trying to show him that seemingly parallel devices may not actually be electrically parallel. But in the first case IF they have a common ground then...

#### MisterBill2

Joined Jan 23, 2018
7,689
This thread perfectly illustrates the reason that I am critical of the arduino theology. Basic circuit theory, including an understanding of series and parallel, in addition to the concept of power being the product of voltage and current, is required even a simple understanding of how things work. SOFTWARE IS NOT ENOUGH, nor will it ever be enough. And picking different names for parts normally referenced by other names is counterproductive always.
To see if something iis in series or parallel one needs to be able to know the flow of current, which we define as being from positive to negative. If the current must flow through one device after leaving the previous device, then the two are in series.

#### WBahn

Joined Mar 31, 2012
26,398
Always have a rough time getting my head around this all. So your saying that my motor shield, and two motors are all in parallel, my controller, magnetometer, HC-SR04, LED and servo are in parallel, but how do they connect up as the motor shield is connected to the controller?
The overwhelming majority of things in a circuit are in their series nor parallel with anything else in the circuit -- series and parallel are simply the two simplest ways to connect two devices, but if we were restricted to only these two ways, electronics would be very limited in what it could do.

What is the problem that you are trying to solve?

#### ebeowulf17

Joined Aug 12, 2014
3,275
SOFTWARE IS NOT ENOUGH, nor will it ever be enough.
I don't think anyone ever claimed it was.

What's the harm in dabbling in electronics in any form before rigorously approaching it from the proper starting point?

Do you begrudge people who started playing with crystal radio kits? I guarantee most of them didn't do a proper study of the inner workings of every single component before they built it. They just put the parts together and marveled at what is capable of. Then, later they learned how to adapt it or build new things based on that knowledge.

What about people who work on their own cars? Most of them end up doing wiring work and learning some electronics knowledge along the way. They rarely start with a ground up, fundamentals only approach to electronics. They tend to think of whole modules and subsystems. In some cases they too develop an interest in electronics, dig deeper, and learn more.

What about RC hobbiests? I could go on and on...

There isn't just one acceptable way to develop an interest in electronics. There might be some ways which are better at establishing the basics early. If you know for sure that you want to be an EE, I'm sure that some teaching methods and tools are preferable to others. But, most people wandering through this site aren't firmly committing their lives to electronics - they just want to play around, try out whatever project it is that they have in mind, and maybe learn something from it. For some, that's as far as it will go. For others, it will spark an interest in deeper learning. If an Arduino is part of what sparks that interest, what's so bad about that?

#### MisterBill2

Joined Jan 23, 2018
7,689
I don't think anyone ever claimed it was.

What's the harm in dabbling in electronics in any form before rigorously approaching it from the proper starting point?

Do you begrudge people who started playing with crystal radio kits? I guarantee most of them didn't do a proper study of the inner workings of every single component before they built it. They just put the parts together and marveled at what is capable of. Then, later they learned how to adapt it or build new things based on that knowledge.

What about people who work on their own cars? Most of them end up doing wiring work and learning some electronics knowledge along the way. They rarely start with a ground up, fundamentals only approach to electronics. They tend to think of whole modules and subsystems. In some cases they too develop an interest in electronics, dig deeper, and learn more.

What about RC hobbiests? I could go on and on...

There isn't just one acceptable way to develop an interest in electronics. There might be some ways which are better at establishing the basics early. If you know for sure that you want to be an EE, I'm sure that some teaching methods and tools are preferable to others. But, most people wandering through this site aren't firmly committing their lives to electronics - they just want to play around, try out whatever project it is that they have in mind, and maybe learn something from it. For some, that's as far as it will go. For others, it will spark an interest in deeper learning. If an Arduino is part of what sparks that interest, what's so bad about that?
I was not talking about developing an interest, I was pointing out that even to play with a crystal radio one needs to understand the very fundamental concepts of series connections and parallel connections. That is totally different from understanding the inner workings of components.

#### atferrari

Joined Jan 6, 2004
4,166
If two things are in parallel they experience the same voltage.
If two things are in series they conduct the same current.
So obvious, so true!

Gracias for putting it in words.