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Topic: Using an external power supply (Read 968 times) previous topic - next topic

UKHeliBob

The general advice is to use an external power supply for servos and not to run them from the 5V line available from the Arduino (Uno in my case).  I fully understand the reason for this and have an external supply.  The 0V lines of the servo and Arduino power supplies obviously need to be connected but is it safe to also connect the positive leads such that the external power supply is providing power to the Arduino ?

When not connected to the USB to provide power I want to avoid the need to have 2 power supplies if I can.  The picture attached will illustrate what I have in mind.

Taking this further I am likely to want to do something similar by powering motors using a 3S Lipo via a motor shield and also using the Lipo to power the Arduino.  The principle is the same as the picture attached except that a higher voltage is involved.
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

DuaneB

yes, you can use a lipo to power an Arduino and escs and servos.

I tend to set up my RC gear as standard and the power the UNO through the vin/gnd pins connect to the LIPO balance plug. The vin pin connects through the UNOs on board regulator to supply 5volts to the chip - don't connect a lipo to the 5v pin directly, this by passes the regulator and will deliver the full battery voltage to the chip probably killing it.

When I say 'as standard' i am assuming from your username that you have BECs etc to supply ypur servos withthe correctvoltage rather than the fully battery voltage.

Duane B
rcarduino.blogspot.com

Read this
http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html
then watch this
http://rcarduino.blogspot.com/2012/04/servo-problems-part-2-demonstration.html

Rcarduino.blogspot.com

UKHeliBob

Thanks for the confirmation.  The servos may or may not be used in conjunction with the motors but, yes, I plan to use a BEC to power them if I do mix and match.  The balance plug of the Lipo is what I had in mind to connect the Arduino to so that the main motor supply can be turned on separately.

Fancy suggesting that anyone would connect an external power supply to the 5V output pins !  Who would do such a thing ?
Confession - me in a mad moment of not thinking.  I can confirm that the USB section of the Uno does not work any more and that the main chip no longer works in another Arduino, but it may be recoverable.
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

retrolefty


Thanks for the confirmation.  The servos may or may not be used in conjunction with the motors but, yes, I plan to use a BEC to power them if I do mix and match.  The balance plug of the Lipo is what I had in mind to connect the Arduino to so that the main motor supply can be turned on separately.

Fancy suggesting that anyone would connect an external power supply to the 5V output pins !  Who would do such a thing ?
Confession - me in a mad moment of not thinking.  I can confirm that the USB section of the Uno does not work any more and that the main chip no longer works in another Arduino, but it may be recoverable.


That could be a dangerous practice as that would be forcing a unbalanced condition between the individual lipo cells and could cause damage when full current is drawn by the motor from all the cells. And while a balanced charger would/could correct the unbalance condition on the next charging, it doesn't prevent damage from unbalanced condition during the discharging of the pack.

Lefty

UKHeliBob

Thanks for your concern, but I am actually going to take the full pack voltage from the balance plug, not just one or 2 cells.  The balance plug is just a convenient way of connecting the Arduino whilst the motor controller is attached to the main Lipo plug.
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

retrolefty


Thanks for your concern, but I am actually going to take the full pack voltage from the balance plug, not just one or 2 cells.  The balance plug is just a convenient way of connecting the Arduino whilst the motor controller is attached to the main Lipo plug.


Ah, so just drawing from the top tap of the balanced connector, that's cool.

Lefty

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