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### Topic: Servo Power Source: External or Internal? (Read 1 time)previous topic - next topic

#### warboyzzzz

##### Mar 19, 2013, 04:28 pmLast 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

#1
##### Mar 19, 2013, 04:34 pm
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

#2
##### Mar 19, 2013, 04:46 pm
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...
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)

#### warboyzzzz

#3
##### Mar 19, 2013, 04:53 pm

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

#4
##### Mar 19, 2013, 05:02 pm
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....
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)

#### DuaneB

#5
##### Mar 19, 2013, 05:59 pm
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
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 pmLast 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.

Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)