6 DOF Robotic Arm

[helal]

Hello guys. I'm new here and I'm wondering if I need a technical help or a priest.

Recently I've purchased a 6 DOF Robotic arm with 6 servo motors (Tower Pro MG996R). First thing I did was test each servo motor. I tested with a servo motor tester board, with arduino and raspberry pi. Everything is ok. So a started assembling the arm. So far so good. Here comes the problem:

When I'm working on a project I like to do gradual steps. So, I started with just one servo motor. When I plug the GND, VCC and Signal wires directly to the raspberry pi board, it is like magic! I can Control the servo the way I want. I know that the MG996R consumes a lot of current and when im working with multiples servos it is good to have an external power source. So, when I connect the servo to the external power source (5V, 2A), wire the grounds together, the servo motor goes crazy. It starts to go back and forth and don't respond to my commands.

I was trying different solutions and I stumbled at something intriguing: if I get 2 wires and connect the GND and VCC from the raspberry pi board to a breadboard and connect the vcc and GND wires from the motor to the breadboard the servo goes crazy again.

Im sorry for my English, I don't know if I made myself clear but I don't understand what is going on. I appreciate any kind of help and if you guys need more information (like the code im using, videos, photos etc) just let me know and I'll be happy to provide it.

Cordially,
Alan Helal

[joan]

Could you post a photo of your connections? I'd be surprised if a servo moved when only connected to ground and Vcc.

[helal]

Hi, thanks for your reply. I made a video showing the servo working when connected directly to the raspberry pi board and then, when connected through a breadboard, it doesn't work.

I don't know hwy this time the servo doesn't start moving back and forth. I checked the raspberry pi VCC output and it is 5V.

Link to video: https://youtu.be/StBPekpyvBo

[pcmanbob]

My first test would be to check the end of the cable you are connecting to the servo to see if you still have 5V on it when you have it connected via the bread board.

[joan]

That suggests there is a fault in the breadboard or in the wires you only use in the breadboard solution.

[monica_palla]

Hello Alan,
When you want to deal with multiple servos at a time, the use of 16-Channel 12-bit PWM/Servo Driver w/ I2C interface is recommended, maybe for over coming the issue which you are facing.