Servos move erratically with power connection

I'm having some trouble controlling the movement of three servos. Two are continuous rotation and one is a high torque servo, all rated to run on 6V.

The problem is that whenever I connect the servos to a 6V battery they spin erratically at full speed. The continuous rotation servos are not so much a problem because they only move a very small amount. The high torque servo however appears to do a 180deg turn. This happens regardless of whether I'm running a sketch, or if I disconnect the signal wires and just connect the battery terminals directly to the servo.

Is this something intrinsic to all servos or am I missing some fundamentals here? How could I possibly fix it?

I would appreciate any advice here, even if it's a stab in the dark. Cheers.

Do you have all the grounds connected together for proper grounding?

Yes, I'm fairly sure I've grounded them all together. I have the grounds of the servos and battery connected in series to the ground on the Arduino.

or am I missing some fundamentals here?

It does sound like you haven't connected the battery ground to the arduino. I know you said you have but that is the expected behavior when you haven't.

waley: Yes, I'm fairly sure I've grounded them all together. I have the grounds of the servos and battery connected in series to the ground on the Arduino.

The word series is either just a poor choice of word or you may not have it wired correctly. A drawing would help at this point.

Lefty

When you power up a servo it will turn to its programmed position if not already there. If you power it down at a different position to 'home' its likely to do this.

MarkT:
When you power up a servo it will turn to its programmed position if not already there. If you power it down at a different position to ‘home’ its likely to do this.

This ended up being the issue, so thanks for replying :slight_smile: I have been busy with the project the last couple of days and hadn’t had time to reply to everyone else, but thank you everyone!

When I said I had all the grounds connected in series, I was meaning I had all the grounds connected in one column on a breadboard. Was this not the correct way to go about it?

When I said I had all the grounds connected in series, I was meaning I had all the grounds connected in one column on a breadboard. Was this not the correct way to go about it?

The wiring is correct. Parallel would be a better term than serial.

Oh ok, thanks! So much to learn :)

Parallel would be a better term than serial.

Both are wrong. A better term would have been chain to describe the way the grounds are linked. The other way to do it is star where all the grounds meet at one point.