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Topic: Using multiple devices and power supplies with Arduino uno (Read 99 times) previous topic - next topic

darkmatter820

Hi everyone,

I'm a bit confused on how to ground my set-up. I'm using a 12V power supply, a 5V power supply (not from the Arduino), a motor, and an Arduino Uno. The Uno will have an external power supply and it'll be connected to a computer when using.

Since there are multiple devices connecting to the unit, I'm not really sure how to ground them all. I've seen threads suggesting that all units should have a common ground. Is this still true if I have the Uno connected to a computer?

Thanks in advance!

Wawa

Confused too.
The Arduino is grounded to the PC/laptop through the USB lead.
A motor driver needs power/ground/signal connected to the Arduino.
Post a diagram/picture of the setup.

12volt (DC socket, V-in) is borderline for an Uno.
It's internals are powered with 5volt, so 7volt has to be dropped by the onboard regulator.
That means you can only draw <=100mA from any pin (including the 5volt pin) before the regulator overheats and shuts down (if you're lucky).
Much better to use a 7.5volt or 9volt supply, or a 5volt cellphone charger connected to the USB socket (bypasses the 5volt regulator).
Leo..


terryking228

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

Paul__B

Since there are multiple devices connecting to the unit, I'm not really sure how to ground them all. I've seen threads suggesting that all units should have a common ground.
It means that every device connected to the Arduino must have its ground, which is also the ground of its power supply, connected to the Arduino ground.  There is a notable exception - with the opto-isolated relay modules, the ground of the module must not be connected to the Arduino but instead the "Vcc¬∑JD-Vcc" jumper must be removed, the "Vcc" connected to the 5 V of the Arduino and the ground and "JD-Vcc" connected to the relay power supply.

Is this still true if I have the UNO connected to a computer?
Clearly - this is axiomatic.  This may present problems since even most laptop supplies have a ground connection to the power outlet and where other equipment has its ground connected to a different, even distant outlet, there may be spurious currents in the ground reticulation which can cause troubles, even burning cables as related on another thread here.  And the solution is most certainly not to fail to connect the grounds of the modules.  :smiley-eek:



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