meArm servo problem

Projects General Guidance
1

Hi everyone !

I'm making the meArm project ( http://lifehacker.com/build-a-kickass-robot-arm-the-perfect-arduino-project-1700643747 ) and everything is fine on the mechanical part of it.

I am using a 7.2V RC battery (6400mAh I think) connected to a voltage buck converter with an output of 6V (I tried 5V as well).

With one servo, everything works fine. With 2, they start to stutter, but when I connect 3, it's really bad.

I saw that to prevent the stutters/jiggles, I could use capacitors and I think I used them correctly but it doesn't fix the problem. Should I use something for the buck converter as well ? It's this one : http://www.ebay.com/itm/151365317684?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I used a bigger buck converter previously but it doesn't change anything.
I wrote the code again but that's not it.

I am pretty sure I'm missing some important informations so I'll write them as soon as possible when you point them out. And I'm new to electronic/programming.

Thank you,
Vincent.

2

Sounds like the buck inverter may not be an adequate power supply. Look at UCEBs on ebay which are made for servo powering. Also make sure you are not powering the servos thru the arduino. The attached pix shows an external servo power setup.

servo-wire.jpg

3

Hi Zoomkat. That's exactly how it's wired, the arduino powers nothing, not even the potentiometer. I'll actually try that and see if it changes anything.

What are UCEB ? I can't find it on google.

I bought last year an arduino shield for motors and I'm pretty sure there're pins for servos. I'll give this a try and see if the buck inveter is the problem.

Thanks for the reply,
Vincent.

4

What are UCEB ? I can't find it on google.

Typo, try UBEC like below.

5

It's all good now, the problem was coming from the potentiometers connected to the 5V from the buck converter and not the arduino. But I'll keep the UBEC in mind in case something ever happens.

Thanks for your help.

6

Kirua:
the problem was coming from the potentiometers connected to the 5V from the buck converter and not the arduino.

Glad you got that sorted, but I'm keen to know what the problem actually was and how you resolved it.

7

The problem was like the potentiometers were always moving back and forth by just a few degrees. I have no idea why it would do that because I just assumed that 5V is 5V. But apparently, the 5V from the arduino are needed.

But good I figured it out, maybe it will help someone someday :slight_smile:

8

I have no idea why it would do that because I just assumed that 5V is 5V. But apparently, the 5V from the arduino are needed.

If the buck converter is powering the servos, its voltage probably swings when the servos move, causing the pot output to the arduino also swing.

9

That could be it. I'll mesure the output voltage of the buck converter when a servo is moving to see if the voltage changes. But anyway, now it's fixed. Hopefully I won't have anymore big problems in the future.

Thanks.