Arduino + Motor shield grounds wired

Should the arduino ground and the motor shield ground be wired together? i came across that :

i have a motor shield and an arduino working together(similar project shown on the picture) however i don't ground them together, should i? Why ? i think they work fine !! :roll_eyes: :roll_eyes:
arduino has its own power source(9V), motor shield too(12V)..

:smiley: :smiley:

Shields have ground pins... they plug into the Arduino ground sockets...

MarkT:
Shields have ground pins... they plug into the Arduino ground sockets...

i don't really understand sorry :disappointed_relieved:
my motor shield is like the one above, i cant plug it to the arduino... so either i wire the grounds as shown or not.. do i have to do that? and if yes why? :~ :~ as i told before they are powered separately and right now the grounds between arduino and motor shield are not wired.. both arduino and motor shield function ok.. i just came across that, that's why i'm asking..
thanks again :slight_smile: :slight_smile: :slight_smile:

that's a really nice picture i found and it shows exactly what im asking... why is that common ground between arduino and the mini motor driver on the picture bellow ?

If you look at the power pins available on any of those non-shield motor drivers, almost without exception there are THREE PINS
ONLY ONE OF THEM IS GROUND. (the other two are logic power and motor power) so your question about WHY you need a common ground does not make sense in view of the fact that you are given no other options. If you connect the ONLY ground on the driver , you are automatically connecting the battery with a common ground because the driver uses the same ground for both logic and motor power. If you can propose some other wiring that makes it possible to NOT have common ground, then you question would make sense. So far I don't see any other options if you are using one of those L298 drivers since they only have ONE ground connection.

raschemmel:
If you can propose some other wiring that makes it possible to NOT have common ground, then you question would make sense. So far I don't see any other options if you are using one of those L298 drivers since they only have ONE ground connection.

i ll answer with a picture :

Do you see any common ground between the motor driver and the arduino at the above picture? I don't ... :wink:
However i came across some projects where there was a wiring between the two grounds(arduino and motor driver), i think the right thing is to be grounded together...

I don’t see any logic power from the arduino to the driver either . How do you think the arduino can communicate the drive signals to the driver without a ground ? Think about it Look at the data sheet for the L298. Your picture isn’t much help although it does show nothing connected to the 5V logic power pin. If you look at photos of other L298 drivers you will see only three pins for power, one ground, logic power and motor power. If you know ANYTHING AT ALL ABOUT ELECTRONICS then you know all control signals MUST HAVE A RETURN (ground). You cannot simply connect IN1, IN2, IN3, IN4, ENA, & ENB without also connecting the ground, the pin in the middle of the THREE PIN SCREW TERMINAL. If you connect that and then the battery, guess what ?
You have a COMMON GROUND.

FYI, the fact that you found a photo on the net does not mean all the necessary connections were made at the time of the the photo. Admittedly, you would expect the person to at least connect the ground before snapping the photo, but apparently they did not.
see attached pinout for L298

HOW MANY PINS DO YOU SEE LABELED " GROUND" ?

Does you question still make sense ?

L298N_pinout.gif

raschemmel:
it does show nothing connected to the 5V logic power pin.

That's a 5v output, you use it if you need it :wink:

If you know ANYTHING AT ALL ABOUT ELECTRONICS then you know all control signals MUST HAVE A RETURN (ground).

If you connect that and then the battery, guess what ?
You have a COMMON GROUND.

I don't get why you use caps, do you know everything about electronics? I found some really good answers why we use common ground:
-- By using a common "ground", the relationship between the hundreds of sub-circuits in an electronic device are maintained and managed. Currents in electronic circuits generally split, switch or vary between multiple paths that have to recombine at some point.
--This is a convenient way to tie all points with this circuit ground symbol together. For safe voltage levels or insulated enclosure
--To connect various circuits or circuit parts together systematically to a single common point (called "ground") in order to avoid building loops which can carry circulating currents which in turn cause disturbance (typically hum). In this case the "ground" may or may not be earthed.
That's what i was expecting as an answer.. :wink: :smiley: :smiley: :smiley:

FYI, the fact that you found a photo on the net does not mean all the necessary connections were made at the time of the the photo.

what posted works, i tested it, without common ground...( but i got the meaning of the common ground and why is used)

see attached pinout for L298

Trust me i know the pinout of l98n
HOW MANY PINS DO YOU SEE LABELED " GROUND" ?

Does you question still make sense ?

My question make's sense for people who know they don't know everything :wink:

what posted works, i tested it, without common ground…

Post a schematic of the arduino controlling the module with no connection from the arduino gnd to the module.
What your saying doesn’t make any sense . Post some proof other than that photo because I never heard of a digital signal working without a ground return so I don’t know how the arduino could control the module.

I don’t see how it could work with no ground connection to arduino. Are you saying you can send a control signal to the L298 module
from the arduino with no ground connection ?

see attached schematics.

That’s a 5v output, you use it if you need it

Agreed (now) after finding a schematic that shows a 5V regulator on the module.

arduino_L298 (1).jpg

l298n-motor-driver-module_02.jpg

raschemmel:

what posted works, i tested it, without common ground..

Post a schematic of the arduino controlling the module with no connection from the arduino gnd to the module.
What your saying doesn't make any sense .

Are you saying you can send a control signal to the L298 module
from the arduino with no ground connection ?

yes and it works..

see attached schematics.

That's a 5v output, you use it if you need it

I don't think so . Post the schematic that shows a 5V regulator on the module.

LM2937 is a voltage regulator , as you see outputs 5v :wink:
Not to be confused i never said the L298N has a voltage regualtor by it self 8) 8) 8) 8)

what posted works, i tested it, without common ground..

That's not what I said. Does it work without ANY ground. ?
If you had a ground from the arduino where did you connect it to the module ?
All the schematics I am finding for those modules only show one ground.

raschemmel:

what posted works, i tested it, without common ground..

That's not what I said. Does it work without ANY ground. If you had a ground from the arduino where did you connect it to the module ?

Let me explain again , i started that post because i saw a picture of a motor driver being grounded together with an arduino(common ground).. However in , my project they are not grounded together.. and working
So i wanted to understand( i was missing something i know :zipper_mouth_face: :zipper_mouth_face:) why they are commnly grounded and i think i already did..
you see this :
]
in my project there is no common ground, each circuit has its own
So i guess in my project, i have to ground arduino with the motor driver(one common ground ) so i don't face any problems.. like the diagram above.. aggreed?

As long as you understand that the term “Common Ground” is a reference to “electrically common” and not a reference to physical location then you should still use a common ground. You still have not explained how your “project” could have separate grounds when the module only has one ground connection. (see attached). That’s why the photo in your first post showed the battery connected to the same pin as that the arduino ground was connected to. Until you can show a second (other) pin that would allow two separate circuits two be connected to the L298 module you still haven’t proved anything. I am glad you found the answer to your question (it’s probably better that you found it that way) but claiming your project has separate grounds and saying you are using an L298 module that only has one ground connection are conflicting statements. Post a photo of your driver module that shows that it has two different ground inputs , one for the uC and one for the motor power battery, because suggesting that you have the motor battery grounded to the L298 but don’t have the arduino grounded to it is just not believable because it defies
the laws of physics (or electronics). I need to see proof to be convinced.

L298_module_pinouts.JPG

raschemmel:
You still have not explained how your “project” could have separate grounds when the module only has one ground connection. (see attached).

How many grounds on that module ? more than one ! (yellow pins on he right )8)

I need to see proof to be convinced.

That’s a how arduino and motor driver communicate in my project…

There is no common ground , i mean exactly what you see in the diagram above, no common reference

Ok. So far so good. Do me a favor and get a meter and check for continuity between the gnd you pointed out and the motor power grn

raschemmel:
Ok. So far so good. Do me a favor and get a meter and check for continuity between the gnd you pointed out and the motor power grn

Ok , just did , no continuoty between arduino and motor driver grounds !!

Ok You win. I stand corrected. If the module has separate gnds it IS poasible

raschemmel:
Ok You win. I stand corrected. If the module has separate gnds it IS poasible

Ok but i think i have to ground them together to be on the safe side..
What do you think ? 8) 8)

I would recommend it.
Zoom in on the photo I posted in Reply#11. (no separate gnd, only one ground. Notice the similarities and differences.
The jumpers are a different color but the headers in front are the same color. The motor power connector is the same color but the the two motor connectors are green. Overall, it is very similar but you can see there is no extra ground in front.

raschemmel:
I would recommend it.
Zoom in on the photo I posted in Reply#11. (no separate gnd, only one ground. Notice the similarities and differences.
The jumpers are a different color but the headers in front are the same color. The motor power connector is the same color but the the two motor connectors are green. Overall, it is very similar but you can see there is no extra ground in front.

i have the one with the yellow ground pin on the front, so i guess i ll use that one to ground it with my Uno..

Yours has 8 pins in front. The other one has 6