Analogue vs Digital Servo's, with long cables.

I want to control a device using a servo, as i need 180 degree rotation. Problem is the device can be far away, so i tested a trial length of 5M of telephone cable, with 4 cores.

The normal Tower Pro 9G SG90, worked, but had slight jitter when stationary. I added a 470mF capacitor at the servo end of the cable and its perfect, zero jitter !!! I Believe this is an Analogue servo.

Next i tried a Tower Pro SG-5010 Digi servo, and it does nothing except buzz a little at the end of the 5M telephone cable. However it works perfectly, connected to the Audrino board and 4AA battery pack. Aurdino i still powered by the USB cable. Absolutely nothing i did could get it to move, at the end of the cable. I also tried 6AA batteries but no joy.

Interesting tests so far, with the SG-5010:

  • If the SG-5010 is powered directly with the battery pack, (at the end of the Telephone cable), AND the signal is run through the 5M telephone cable, it works fine.

Thus at this point, i think its a power problem because the digital servo does not like the small telephone cable gauge. I will try some thicker cable perhaps.

Just wondering if anyone here has run servo's over long cables ? Seems Analogue Servos are more tolerant to long cables.

I should add, that i am learning Audrino, and have a kit to play with. I am driving the servo's using the sample code. But i dont think this a code problem. Perhaps a servo problem, as there are many robotic projects with quite long cables.

Be careful with your voltages - servos are easily damaged if seupplied with too high a voltage ( esp digital ones)
Yes a bigger diameter cable a good idea as is using a capacitor at the servo end.
There maybe better solutions such as having the battery pack powering it next to the servo

Good Morning,

Problem solved !!

Exact same setup, but i changed the 5M cable to Cat 5, from the local hobby store. (Jaycar)

Used one of the twisted pairs each, for Signal, +Ve and -Ve. ALL remaining wires were connected to -Ve, which is also connected to the Audrion's Ground.

Servo is powered with 4x AA batteries. Arduino is powered by the USB power.

Works 100% and it totally stable without the capacitor, but i did buy a 4700uF one to add.

Will try 10M next..


You should never connect a large value capacitor directly across a logic signal, that's going to overload
the pin. A few 100pF is the maximum most logic devices are ever spec'd for.

You can add say about 220 ohms in series to limit the current and reduce signal reflection, then add a
capacitor, but 10nF is usually plenty.

And 470mF means 470000 microfarads, The symbol for micro is ยต, or u, never m or M (M is mega).