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Topic: Servo acting weird (Read 4135 times) previous topic - next topic

Ryotsuke

Arduino Nano, Servo SG-90, +9 V PP3 battery, stabilizer +6V L7806
Stabilizer has two outputs: 2. +9 V directly from the battery, 1. +6 V
B. is Voltage in for Arduino
A. is Voltage in for Servo

(See attachment)

First it was connected like: 2 -> A, 2 -> B
This option works great. But I'm afraid to burn the servo, though the load it is episodic. (Loads last for 0.1 second not more than once per second)

If I connects via stabilizer: 1 -> A, 2 -> B
Servo goes crazy - goes from 0 to 180 and back infinitely. Arduino board is operating normally.

I tried option 1 -> A, 1 -> B - in this embodiment, servo emits strange sounds, Arduino does not work.
Option 1 -> B, 2 -> A works perfectly, but it defeats the purpose of the stabilizer, the servo is still +9V

Questions:

1. What's going on and how to fix it? I'd like to use 1 -> A, 2 -> B
2. Is it possible to feed servo from +9V. If it does not work all the time, it may work normal?

retrolefty

Typical servos voltage ratings are 4.5 to 6.0 vdc, operating them at 9vdc is most likely will only cause damage to the servo. Your most fundamental problem is that a PP3 battery is just not a good match for powering a servo even if you use a 6vdc regulator, because of the current draw requirements of a typical servo. A battery pack made up of AA alkaline cells is a better match if you must use batteries, or a suitable rated 1 amp wall wart power supply. If running multiple servos allow current capacity of the power supply of 1 amp per servo.

Lefty

Ryotsuke

Battery size is critical. And actually PP3 has enough power to run this circuit as is clearly seen when board is connected without regulator. I don't need to run this for long. Even if battery will drain in 10 minutes - it's fine - it is Li-ion rechargable :)

Ryotsuke

b.t.w. I use "small" version of L7806(0.1A) currently, I'll try full-size L7806 version (up to 2A) in the evening and tell if it works

AWOL

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If running multiple servos allow current capacity of the power supply of 1 amp per servo

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I use "small" version of L7806(0.1A) currently,

Hmm.

Ryotsuke

#5
Mar 07, 2012, 10:42 am Last Edit: Mar 07, 2012, 10:47 am by Ryotsuke Reason: 1

Hmm.

It is small servo with minimum torture that is powered on for like 0.1 sec in long periods. Show me a good site to look for load CURRENT (not only VOLTAGE) datasheets for servos. Was I supposed to know this telepathically?
I have used 5 x 13kg/cm servos and they consumed <2A when used same time.

PS Though I still hate that almost no site provides load CURRENT for servos they sale

AWOL

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and they consumed <2A when used same time

Yes, but 2A is still MUCH greater than the 100mA your regulator is rated for.
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It is small servo with minimum torture that is powered on for like 0.1 sec in long periods

Moving a servo for a short time is almost guaranteed to give you worst-case current consumption, I would have thought.

Ryotsuke

Ok, clear. I'll try with bigger regulator. Hope that was the problem.

Techone

I did some tests on servos. I use the "pot" code, the servo current usinf an external +6 V and test the current.  One servo on continous mode and the other "normal' servo. The current is : about 150 mA for the continous ( move CW or CCW ), and 50 mA to 200 mA for the normal type ( move & stop ) 

Therefore, when you use a servo, design for 250 mA for each servo. The more servos, the more currents it will eats. And using a battery to power them, expect the battery to be drain pretty fast... If I was making a robot using motors & servos, I will be using a car battery for LOL.  Go Ahead, Drain This ( car battery ) !!!   ]:)

The motto is :  Electric Motors Eats Currents for Breakfast   :D

AWOL

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I did some tests on servos.

What was the load on the servos?

Techone

#10
Mar 07, 2012, 11:43 pm Last Edit: Mar 07, 2012, 11:45 pm by Techone Reason: 1
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What was the load on the servos?


At no load condition. ( the servo have gears )

I was simply curious about them.

And I expect the current of the servo to increase when a load is apply.

I test those servos :  GWS S03N STD  <-- Standard Servo
                            GWS S35 STD  < Continious Servo

Ryotsuke

Used more powerful stabilizer and now it is fully working.

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