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Topic: Servo Motor doesn't move although 5V (Read 5203 times) previous topic - next topic

Rachmaninow

Hello Guys,

I dont get it anymore... I want to power a servo Motor with a 9V-Battery. So i bought an LDO which transfer it to 5V and max. 5A. Should be enough for a servo i think?

Well i tried it, and measure the 5V at the servo (so the circuit is correct!). Although the servo has 5V, it doesn't move! Why?! I think it doesn't flow a current.

If I power the Arduino with the 9V Battery (Vin), everything works fine. So where is the problem?

P.S. I use the Sweep-Example-Code for debugging.

jremington

#1
Nov 20, 2015, 10:26 pm Last Edit: Nov 20, 2015, 10:27 pm by jremington
The rectangular 9V batteries are for smoke alarms, not motors.

Rachmaninow

well thats no answer to my question :/

what would you suggest instead of a 9V battery?

and still the old question: why doesn't do the servo anything?

MarshaJ847

Are the grounds on the Arduino and the Servo's power source connected?  If not, the pulses from the Arduino wont be read correctly.

Marsha

jremington

Quote
well thats no answer to my question :/
Let me try to be clearer:

A rectangular, 9V battery of the type used for smoke alarms cannot power a motor.

Solution: use a different battery. 6AA cells will power small motors for a while.
As the previous poster suggested, be sure to connect the grounds together.

GrooveFlotilla

Quote
I want to power a servo Motor with a 9V-Battery.
Servos are normally only rated to 6 V
Some people are like Slinkies.

Not really good for anything, but they bring a smile to your face when pushed down the stairs.

DrAzzy

Servos are normally only rated to 6 V
Which is why he says in the next sentence that he was powering it through a 5v LDO....
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Rachmaninow

Are the grounds on the Arduino and the Servo's power source connected?  If not, the pulses from the Arduino wont be read correctly.

Marsha

Thank you, that was the solution!

@Groove: I use a LDO?

@Others:

Well, i need to have a light-weight solution. Its a System on a drone, so it should be very light.
If I put four of this Batterys in serial, i should have 6V with 3000mAh, right?

Energizer Lithium-Batterie Mignon AA, 1,5V, 3000 mAh
(http://www.elv.de/energizer-lithium-batterie-mignon-aa-1-5v-3000-mah-4er-pack.html)

Do i need a LDO at 6V, or can i connect the 6V directly to Servos?


Also:
I measured this current consumption: 200~300 mA. So the solution with the battery-pack would keep up to atleast 10 hours?

DrAzzy

The servos are okay with 6v.

Note that the Arduino itself is not. If you put it into Vin, the arduino will be getting 4.x volts, due to the dropout on the garbage regulator the Arduino boards use. But it's too much to supply direct to the 5v pin (you could use that LDO to get the 5v, and put the 5v output of that into the 5v pin - but if you do that, you must not connect it to USB while it's powered that way, lest you risk damage to the board)

ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

Rachmaninow

The servos are okay with 6v.

Note that the Arduino itself is not. If you put it into Vin, the arduino will be getting 4.x volts, due to the dropout on the garbage regulator the Arduino boards use. But it's too much to supply direct to the 5v pin (you could use that LDO to get the 5v, and put the 5v output of that into the 5v pin - but if you do that, you must not connect it to USB while it's powered that way, lest you risk damage to the board)


Mhm im not sure if I understood what you tried to tell me :/

So i place 4x 1.5V in serial = 6V. THose 6V goes direct to the servos. Parallel to that, 6V goes to the Vin of the Arduino. Shouldn't be a problem, or? On my other arduino, i feed it with 9V into Vin. works fine.
I have readt, that Vin shouldn't be >12V, so the onBoard-LDO gets too hot and damages the board.

Well, i think i need special akkus for servo Motors? Btw: there are two servo-Motors to feed :/

OldSteve

Mhm im not sure if I understood what you tried to tell me :/

So i place 4x 1.5V in serial = 6V. THose 6V goes direct to the servos. Parallel to that, 6V goes to the Vin of the Arduino. Shouldn't be a problem, or? On my other arduino, i feed it with 9V into Vin. works fine.
I have readt, that Vin shouldn't be >12V, so the onBoard-LDO gets too hot and damages the board.

Well, i think i need special akkus for servo Motors? Btw: there are two servo-Motors to feed :/
6V isn't high enough for the Vin of an Arduino. There is a forward voltage drop of 1V to 1.2V across the regulator.
Recommended voltage for Vin is 7VDC to 12VDC.

And 6V is too high for the +5V connection of an Arduino.

Unfortunately, 6V is right in the middle - in limbo.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

MarkT

#11
Nov 21, 2015, 02:47 am Last Edit: Nov 21, 2015, 02:47 am by MarkT
Don't try powering the Arduino and servos from the same power source.  Nearly all the problems
people have with servos are power related.  Most servos need 1A or so peak, more than USB can
provide, much more than small 9V batteries can possibly supply, and servoe put spikes and noise
onto the supply that can damage or reset logic chips.

Motors/servos on one supply rail, logic on another (regulated and spike/dropout free) supply. Common
the grounds at the Arduino. Thats the key to trouble free behaviour.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Rachmaninow

Thank you for your answers.

I want to power the whole system by one Power-Supply.

So, I need a battery with big capacity, light and high current. Price doesn't matter. I connect this battery to the servo-motors via LDO (5V). Parallel to that, i connect it to the Vin of the Arduino..
So the battery has to be >7V?

Maybe, 5x AA (7.5V)? But its not a nice solution... there are a only attachment for 4x AA, not 5x.

OldSteve

#13
Nov 21, 2015, 09:55 am Last Edit: Nov 21, 2015, 09:57 am by OldSteve
Thank you for your answers.

I want to power the whole system by one Power-Supply.

So, I need a battery with big capacity, light and high current. Price doesn't matter. I connect this battery to the servo-motors via LDO (5V). Parallel to that, i connect it to the Vin of the Arduino..
So the battery has to be >7V?

Maybe, 5x AA (7.5V)? But its not a nice solution... there are a only attachment for 4x AA, not 5x.
5 x AA isn't "big capacity", particularly if running two servos. And don't forget that your battery voltage will drop during discharge, so ideally you want 7V or a little less "at the end of discharge", not fully charged.

If I were you, and cost wasn't a concern as you say, I'd go with a NiMH or, better still, a Li-Po battery. 7.2V to 7.4V. They start out at 8V+, and drop to <7V when fully discharged.

How long do you want between recharges?
To determine battery capacity, you need to take that into account.
For 3 servos, the arduino itself and a few extra low-current peripherals, I use a 7.2V 4800mAh Ni-MH battery, which gives me a few hours between recharges. I've never taken note of the exact time - might be 4 hours.
(I recharge when the terminal voltage drops to about 6.5V or a fraction lower.)

Is your 5V 5A regulator linear or switching?
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

#14
Nov 21, 2015, 10:34 am Last Edit: Nov 21, 2015, 10:36 am by Rachmaninow
Thank you OldSteve, the first precise answer :)

LiPo sounds nice, also a 7.4 Voltage is fine.
Well, i send sensorvalues via 433 MHz on this arduino, who shall controll 2 Servo-Motors. So with 4800mAh, it could be 4-5 hours? Sounds nice.
So i had a look on this battery:

http://www.kotte-zeller.de/LRP-LiPo-Akku-7-4V-3800mAh-30C-Hyper-Pack-Multi-Plug-Hardcase-430215.htm?websale8=kotte-zeller-shop&pi=902017


Well, it has a nice capacity but its way too large and weights to much i think... :( Never thought, that battery-management is so hard.

My 5V regulator is a linear one. "LM1084" (http://docs-europe.electrocomponents.com/webdocs/0780/0900766b807800b5.pdf)



EDIT:
I found this one:

http://www.kotte-zeller.de/Dynamite-Reaction-LiPo-Akku-7-4V-4000mAh-50C-Sub-Hardcase-EC3-DYNB3800EC.htm?websale8=kotte-zeller-shop&pi=901974

its smaller than the other one, has more capacity


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