Problem with servo movement

[dasoul]

Hi,

first post on the forum. I have a project using an Arduino Uno, a Towerpro MG996R servo motor and a Li-po battery and a Charger and 5v boost board. It's a spherical die, which swings an arm inside of it with a weight and it makes the die roll. The problem with my project is that as long as the Arduino is connected with a USB cable the code works. The crazy part (for me at least) is that the usb doesn't even have to be connected to a computer or an outlet - it just needs to be connected to the power adapter. Once I take it out the servo starts to go past the programmed parameters. Here is the code I'm using:

#include <Servo.h>

// Declare the Servo pin
int servoPin = 9;
// Create a servo object
Servo Servo1;

void setup() {

  Servo1.attach(servoPin);


}

void loop() {

  Servo1.write(100);
  delay(4000);
  Servo1.write(151);
  delay(4500);

}

I've tried using multiple charging and boost boards, all with the same result. I'm attaching the schematic of the battery charge and boost board. I'm guessing there is a component in the power adapter that makes it work properly, but I don't know what it is. Any suggestions are highly appreciated.

[wvmarle]

Quite certainly a power supply problem.

What is the current rating of your boost converter?

What happens if you run the project off a pack of 3 AA batteries, without boost converter?

[dasoul]

It's 2000mA.

If it's a power supply problem, why it doesn't matter if the power adapter is connector to power or not?

[slipstick]

So what does happen if you replace the Lipo/charger/boost board with 3 x AA batteries? Or even better 4 x 1.2V NiMH rechargeable AAs.

And how is the MG996R connected? Not to the Arduino 5V pin I hope. In fact how about a schematic showing all connections.

Steve

[wvmarle]

dasoul:
If it's a power supply problem, why it doesn't matter if the power adapter is connector to power or not?

It seems like the power adapter (battery charger, voltage boost) is the problem. No matter how much power you have available for it on the input, it appears to be unable to deliver enough power on the output.

[TomGeorge]

Hi,
Welcome to the forum.

Do you have a DMM to measure some circuit voltages?

Thanks.. Tom..

[dasoul]

Hi Tom,
Yes I have. I've measured what is coming in the booster and what is coming out of it: 3.72v and 5.02v respectively. Should I measure somewhere else?
Thanks!

[dasoul]

wvmarle:
It seems like the power adapter (battery charger, voltage boost) is the problem. No matter how much power you have available for it on the input, it appears to be unable to deliver enough power on the output.

5v are coming out of it. I don't know if I'm saying this correctly but all is working properly as long as there is a usb cable plugged into the Arduino and into a power adapter (the adapter is not connected to anything, no electricity is coming from it) and all of the power comes from the booster/charger circuit.

[TomGeorge]

dasoul:
Hi Tom,
Yes I have. I've measured what is coming in the booster and what is coming out of it: 3.72v and 5.02v respectively. Should I measure somewhere else?
Thanks!

What about when the problem occurs?
Can you post an interconnecting diagram of your project, include power source, controller and servos.
Thanks.. Tom...

[wvmarle]

That there is 5V coming out right now doesn't mean there's still 5V coming out of it for the few milliseconds upon the starting of the motor of the servo. Such a dip is plenty for an Arduino to get reset.

In my experience USB power is remarkably robust, even if limited to some 500 mA it seems to handle peaks from starting servos really well.

Maybe all you need is a bigger decoupling cap on the output of your boost converter. Start by adding 220µF, maybe ramp it up to 1000 µF even. That should take care of the inrush.