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### Topic: Multiple servo switch on load issue (Read 5932 times)previous topic - next topic

#### Robin2

#15
##### Feb 16, 2015, 12:06 pmLast Edit: Feb 16, 2015, 12:14 pm by Robin2
Quote
The signal lines shouldn't be floating in at least two of those cases, however the issue persists.
I wonder how many catastrophes have happened because things "shouldn't" have ...
The Titanic and the Space Shuttle spring to mind.

Quote
Also, keep in mind a wire is a resistance,
IMHO this is grossly over theorizing the problem

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### 1:1

#16
##### Feb 16, 2015, 10:48 pmLast Edit: Feb 16, 2015, 10:55 pm by 1:1
You're implying that I shouldn't assume things or catastrophe awaits, it's possible yes, but improbable given the circumstances. (strawman argument in essence?)

...you then humbly imply that I shouldn't over theorize.

You simply mean to say that we'd get along better if I had the same ideas and experience as you?  (The porridge is juuuust right )

So far it would appear that I don't - but lets not let that stop us from learning right?

To me more specific:

You suggest that lines supplying PWM should start floating when I power up a unit that they are supplying? That's not something I have the conceptual background to appreciate. Elaboration, if possible ?

Also RC circuit theory isn't exactly egghead territory - (obviously) I'm no expert - but I do understand you can't comprehend them without understanding the (basic) nature of resistance.
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

#### Robin2

#17
##### Feb 16, 2015, 11:25 pm
You suggest that lines supplying PWM should start floating when I power up a unit that they are supplying? T
What I suggested was to connect some 4k7 resistors between the signal wires and GND and see if that was beneficial for your problem. That takes about 5 minutes of your time.

I am not suggestiing what I have quoted above. I am trying to put in your head the idea that when the Arduino starts it is not outputting any servo signal and the poor servo has to figure out all on its lonesome what it should do. Some servos are not happy in that situation. This is not theory.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### 1:1

#18
##### Feb 17, 2015, 12:43 am
Once again (feels like the third time, but I'm going to refrain from counting) I reiterate that in tests where the arduino (and also pololu servo driver) are already powered on the issue persists. They are on separate supplies, something you assumed in post #6.

So while agree with you on your second point re. startup signals being for all intents and purposes random (or prone to give unexpected results etc.) - it would seem it is not relevant to this case - yes/no ?

Also:

- So you're suggesting I 'should' have 10 4k7 resistors on me?  ...imminent shuttle disaster?
- You haven't explained what/how resistors would help - I think you said 'steady' the signal- I'm keen to learn (not being sarcastic). You're tying the line to GND - a pull down resistor?
- Did you by chance miss the part where the cap helped?   i.e. likely just need another cap in parallel or a larger value single unit and I'm good

Phew !  something about some Arduino forum users that gets me going I tells ya.

Discussion is robust
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

#### Robin2

#19
##### Feb 17, 2015, 10:20 am
Phew !  something about some Arduino forum users that gets me going I tells ya.

You are making a big deal about something that was never intended to be a big deal. And maybe I missed a simple answer that would have made it clear that it was not a solution. If you look at the Reply where I I first mentioned it you will see that I was not really expecting much from the idea. However, all along I have had the impression that the problem you are describing is a startup problem.

When you say "I reiterate that in tests where the arduino (and also pololu servo driver) are already powered on the issue persists" do you mean that you power up the Arduino to the point where it is issuing servo signals and then "throw the switch" to connect power to all of the servos at one time?

And (sorry if I am asking you to repeat yourself) if you "throw the switch" in the same way but without the Arduino powered does the same thing happen?

If it does, it suggests to me that the power supply for the servos is inadequate and the simple way to test that is to try a bigger power supply.

I know very little about electronic theory. I just know that the 4k7 resistor solved a startup problem for me where the servo was moving while the Arduino was resetting.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### 1:1

#20
##### Feb 17, 2015, 11:19 am
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

#### Robin2

#21
##### Feb 17, 2015, 02:23 pm

For whom?

I want to minimize my reading so I have time to attend to other requests for help.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### 1:1

#22
##### Feb 17, 2015, 07:50 pmLast Edit: Feb 17, 2015, 07:51 pm by 1:1
You are the him to whom I refered.

After looking in the mirror, as you suggest (?) -  I still think my comment applies to you only.

With a post count of 16+ per day, your tactic of minimizing reading so as to optimize your 'attendance' is telling.

Try, if you can, to not reply to this...

Consider it a challenge.

The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

#### Robin2

#23
##### Feb 17, 2015, 10:29 pmLast Edit: Feb 17, 2015, 10:38 pm by Robin2
Consider it a challenge.
I can never resist a challenge like that.

When I ask a question here (or on any Forum) I like to present my question so the person providing assistance can do so with the minimum of effort.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### zoomkat

#24
##### Feb 19, 2015, 06:12 am
Quote
Should also make it clear, the 2.7 and 5A will hold -
That just indicates an inadequate power supply. Servos under load (or starting current) can use more than 1a each (probably more if they are large servos). Also most servos have a lower operating limit of 4.8v. Lower than this and digital servos in particular may have control issues. People uising lipo batteries are able to operate hexapods with 18 servos.