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Topic: Servo Power Source: External or Internal? (Read 739 times) previous topic - next topic

Mar 19, 2013, 04:28 pm Last Edit: Mar 19, 2013, 04:31 pm by warboyzzzz Reason: 1
Now i'm doing my project, controls 6 servos with IR remote, and i wondered if these 6 servos shoul receive Voltage from external(batteries) or from internal (5v from my arduino mega)?
cause i try with 5v pin for 1 servos, it works well. what if 6 servos with 5v pin?

wildbill

Generally it's marginal to run even a single servo from the 5V supply on the arduino; for six you will surely need external power.

JimboZA

Quote
Generally it's marginal to run even a single servo from the 5V supply on the arduino


In this thread, post #19 there's a pic of my servo connected to a plastic hose with a string to bend it like a finger... it was drawing almost 500mA to do that.

warboyzzz, you should test this yourself: just put an ammeter in series with a servo power wire, and hold the servo and horn in your hands to try to stop it turning- the stall current is probably higher than you expect.

wildbill's right: even one servo is dodgy...
My hovercraft is full of eels.

No PMs for help please.
DO NOT power servos from Arduino 5V: give them their own power and connect the grounds.


Generally it's marginal to run even a single servo from the 5V supply on the arduino; for six you will surely need external power.


ok then, so each servo i should put how many volts? so one servo around 4 pieces of AA batteries? so the total is 24 batteries?

JimboZA

Quote
ok then, so each servo i should put how many volts? so one servo around 4 pieces of AA batteries? so the total is 24 batteries?


If you put 6 servos on one pack of 4 batteries they'll still be at 6 volts each.... but it's the current that will be the limiting factor.

You would need to experiment with that, because it depends how much current each draws compared to the current available from the batteries. You might find you can run all of them from one pack of 4, or might need say 2 packs running 3 each....
My hovercraft is full of eels.

No PMs for help please.
DO NOT power servos from Arduino 5V: give them their own power and connect the grounds.

DuaneB

If you put 6 servos on one pack of 4 batteries they'll still be at 6 volts each.... but it's the current that will be the limiting factor.

Not quite true, the voltage will drop as the current approaches the maximum that the batteries can deliver. You will probably need a few sets of 4 batteries or some RC Batteries which are able to deliver much higher currents at similar voltages.

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

JimboZA

#6
Mar 19, 2013, 06:02 pm Last Edit: Mar 19, 2013, 06:13 pm by JimboZA Reason: 1
Quote
Not quite true, the voltage will drop as the current approaches the maximum that the batteries can deliver.


Yeah that's actually what I meant... I should have said "nominally" at 6V

I was trying to point out that in parallel, a number of motors are all still across the 6v terminals and are at 6v, but yes, subject to the drop as you say.

My hovercraft is full of eels.

No PMs for help please.
DO NOT power servos from Arduino 5V: give them their own power and connect the grounds.

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