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Servo could not be moved/controlled
04-02-2018, 01:35 AM (This post was last modified: 04-02-2018 11:47 AM by Mic.)
Post: #1
Servo could not be moved/controlled
Hi @ll,
it's already Easter and I'm still struggling with the servo of the Spherebot.

I can send commands to the board via serial connection tested on com-port 1 or 2. Motors can be moved via SM and "v" gives me the expected version-response, all valid commands replied "OK" but on TP or SP nothing happens.

The servo seems to be controlled, because it moves to a defined position when powering on. It is also permanently "under fire" means it tries to keep the position when I want to turn it a bit off and I can see the typical servo puls-diagramm when I connect an oscilloscope.

I tried it with Leanardo and UNO as well and also with servo directly connected to the boards (without shield). (I hope it will work without shield theoretically). I also used different PC, both Win7/64bit.

Is anybody out there having an idea for a solution - maybe there is a typical arduino-trap i stepped in :-)

Thx
Mic
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04-02-2018, 05:57 PM
Post: #2
RE: Servo could not be moved/controlled
Maybe the servo potentiometer is damages? Does the 5 Voltage regulator of the Arduino/Brain shield get too hot? If the motors can be controlled, the servo should be too, so discard any OS problem or PORT issue. do you have any other servo around?
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04-03-2018, 10:32 AM
Post: #3
RE: Servo could not be moved/controlled
(04-02-2018 05:57 PM)JJrobots JP Wrote:  Maybe the servo potentiometer is damages? Does the 5 Voltage regulator of the Arduino/Brain shield get too hot? If the motors can be controlled, the servo should be too, so discard any OS problem or PORT issue. do you have any other servo around?

First of all -thx for the reply...

No damage, the servo works quite well - I just wrote a small test-sketch with manual timing and random movements of the servo and it works well. And yes, I also tried a bunch of (different) analog servos which I have in spare.

The 5V-regulator does not heat up at all and I also even tried without the brain-shield (Which should work as well for a single servo).

That is what is really disgusting - I can communicate via serial to make the motors run but cannot move the servo... I tried the TP-command without parameters as well as SP,1 or SP,0.

I also tried an older version of the servo.h of older arduino IDE - just to be sure ;-)
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04-04-2018, 11:14 AM (This post was last modified: 04-04-2018 11:14 AM by JJrobots JP.)
Post: #4
RE: Servo could not be moved/controlled
So...maybe the line that goes from the Arduino to the SERVO header is not working? Can you use a multimeter and check if there is continuity?: Arduino D10 pin to SERVO1 header (SIG) (schematic attached)

There is another option here: to change the Arduino CODE in order to activate the Brain shield´s SERVO 2 instead SERVO1


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.pdf  schematic.pdf (Size: 100.95 KB / Downloads: 4)
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04-04-2018, 12:36 PM
Post: #5
RE: Servo could not be moved/controlled
As I wrote in my initial post, the servo itself works in that short moment when the whole thing is powered up - just to turn in it's default-position. And I feel the power in the servo if I slightly try to "detune" the servoposition. Furthermore I measured the signal on the pin of the servo-header right on the shield with an oscilloscope, and I saw the expected signal 20ms cycle duration and about 1,5ms signal width.

So it seems, that only the serial command is not processed correctly.

Btw. I tried a different variation of the EggDuino-code (C-Egg-Bot) that has an improved servo-code. A first test showed, that it works, but due to a different pinout i tested it without shield (and motors). The code uses Pin A3 and I'm not sure if that has something to do with using the analog port.

I will try to change the pinout according to your shield and see if it will work. Then I have to jump the next hurdle, because the incscape-plugin didn't found the board yet.
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