next topic »

[on:]

i built a robot powered by 2 servos SM-S4303R. Before i used a 9V battery for supplying the arduino and servos via the external power supply. all went well and as expected, only battery life was not that long.
Today i changed to a 6 x 1.2V rechargable AA battery powerpack with 2500 mAh each.
Now, connected to the external arduino supply it does not work, servos turn but in reverse direction and not as programmed. Connecting the usb and all is ok at once. i measured the powerpack output voltage as 8.4 V.
btw all AA´s are freshly recharged.

[Reply #1 on:]

The servo seems to be rated upto 6V only.  It may be pulling excess current with that battery pack and becoming unstable.  The 9V battery probably limited the current and thus reduced the loop gain of the servo.   Could you run the Arduino and the servo from 4 cells (4.8V)?

[Reply #2 on:]

MarkT> thanks your input.
justed tryed to run on 4 cells. now only one servo turns, randomly starting foreward or backward direction.

[Reply #3 on:]

Sadly you may have damaged your servos as they are typically rated as requireing 4.5 to 6 volts, with 6 volts as a maximum. 7.5vdc may have been too much.

Lefty

[Reply #4 on:]

Are you using the servos with or without the regulator?

[Reply #5 on:]

i never have supplied anything more than the 5 Volts from the arduino board 5 V outlet, so i think that the servose are fine. They are working perfectly when i power the arduino board with the USB.

regarding regulator - i have connected both servos directly on pins 9 and 10 of the arduino uno board.

[Reply #6 on:]

Are you saying you powered the servos from the Arduino's 5V regulator?
Are these special low current servos?

[Reply #7 on:]

You shouldn't ever run servos from the Arduino's regulator; it is only rated at 500mA.
(Another sticky thread candidate)