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Topic: jittery servos (Read 745 times) previous topic - next topic

TomGeorge

Hi,
Do you have a pair of wires from the supply  to the servos, AND a separate pair of wires from the Mega to the supply.

The aim is for the controller NOT to share power circuit wiring with the servos.

Are you really prototyping on protoboard?

Tom.... :)

Everything runs on smoke, let the smoke out, it stops running....

jremington

#16
Feb 12, 2018, 12:43 am Last Edit: Feb 12, 2018, 12:48 am by jremington
Quote
the fact that the servo power comes via Dupont connection from the breadboard into the servo connector plug.
That is guaranteed to be a problem, which is why I asked about it some time ago. 

Breadboard tracks should never be expected to conduct more that a couple hundred mA, and you are asking one to carry up to 7 Amperes. The track is probably burned.

chopperaddict

Hi Tomgeorge, I think you  have misunderstood my Fritzing diagram ? the servos are powered directly from my lab power supply, the arduino is powered via the USB or a 9v cell.  Only the 2 grounds are connected.

Yes, I am using veroboard so I can solder as many connections as possible, do you not approve ?

Hi jremington, I am not sure where you get 7A current from ?  My servo power supply and DMM show a maximum drain for one servo to switch is no more than 250mA.  There is never a time when more than a single servo is switching at the same time ?

Cheers

TomGeorge

Hi Tomgeorge, I think you  have misunderstood my Fritzing diagram ? the servos are powered directly from my lab power supply, the arduino is powered via the USB or a 9v cell.  Only the 2 grounds are connected.

Which is why we ask for a proper schematic.
A 9V cell will not keep your arduino powered for long.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
A picture of your project  will help, so we can see your component layout please.
Thanks..  Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

jremington

#19
Feb 12, 2018, 05:01 pm Last Edit: Feb 12, 2018, 05:03 pm by jremington
Quote
My servo power supply and DMM show a maximum drain for one servo to switch is no more than 250mA.
Those measurements don't show the full picture. Servos briefly draw the stall current every time they start to move. For small hobby servos, the stall current is around 1 Ampere and sometimes much more. Look up the stall current for your servo and tell us what that is.

slipstick

SG90 stall current is given as 650mA +/-80mA at 5V. So 1A is overdoing it, but not by very much.

Steve

chopperaddict

Hi Tomgeorge

As requested is here is my best attempt at a schematic produced using Fritzing.

I hope it clarifies my layout and design..?


TomGeorge

SG90 stall current is given as 650mA +/-80mA at 5V. So 1A is overdoing it, but not by very much.

Steve
Is not overdoing it, always overspec, never justspec. :o :o :o


Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

TomGeorge

#23
Feb 13, 2018, 10:20 pm Last Edit: Feb 13, 2018, 10:21 pm by TomGeorge
Hi,
Thanks for circuit;

You are powering the Mega from the same 5V supply?
Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

chopperaddict

No Tom, the mega is powered from the USB

TomGeorge

Hi,
What value are your pull down resistors?

How long are your wires from the switches to the Mega and from the Mega to the Servos?

Can you post a picture of your project so we can see  your component layout?

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

chopperaddict

#26
Feb 14, 2018, 01:47 pm Last Edit: Feb 14, 2018, 02:05 pm by chopperaddict
Pulldowns are 10K

Pictures of physical system attached, (including an SD card now attached.)

Hope it makes sense, All ***but*** those duponts on headers and into Arduino are soldered, including my little power distribution board at front and centre. left side is mega power, right is power supply for servos alone, both grounds are connected here with black wire.  All duponts are brand new.
Ian

wildbill

So, with that setup, what do you get if you run the most basic of code - move servo to 45, wait a couple of seconds, move to 90, wait etc.

chopperaddict

Just doing some more soldering, to ensure good contacts on the veroboard, so will try your request once that is finished !

Ian

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