Servo just go crazy

I power up using 4.8V NIMH battery. coonected to PC using USB.
When i connect 3 servo, it work fine.

when i connect 6 servo, all servo goes crazy …they just move non stop aimlessly.
i am using a small servo 3.5kg.

how to trouble shoot…

Hello. This is most likely a problem with your power supply, since it only occurs when you add more servos. Is your battery freshly charged?

If you are using a Pololu product, please tell us which one.


HI, i am using a polulu 12 servo controller. If i am using 6 servo does that means i need 6 A currents.
Please advise how much my battery capacity should be…

Or should i be powering the servo directly and only connect the signal wire to controller ?

To be safe, you should make sure your battery has a maximum discharge rate above 6 A. The maximum discharge rate is related to, but not the same as the battery capacity. For more information, please see this blog post: … h-is-not-a

What is the capacity of the battery you already have? This 900 mAh one from us would probably work:

No, 6 A is not high enough for that to be worth it.


I am using a NIMH 800 mah.
I tried to use 4 AA size nergizer battery.

Both did not work well.

Now should i connect 1 battery pack to 3 servo ? If so what is your suggested connection ?

I think you should be able to get this working with a single battery pack.

What kind of servos are you using and what do you mean by 3.5kg? Was your NIMH 800 mah battery freshly charged? What kind of AA Energizer batteries did you have: Alkaline or NIMH? When the servos were going crazy, did you have the Maestro plugged into USB or not?

I’m not sure what’s going wrong, but if you could give more information about what you are doing, including photos of your connections and videos of how the robot behaves, we might be able to spot the problem.


Hi, thanks for the help. I think the problem is one of the servo torque is too high, so when i on it, the current drawn is too high and probably caused other servo to go crazy …
you are right, the battery pack i have should be sufficient.

I will keep trying and let you know if i face some more problems.
Thanks as my students are trying to get it work to complete their project on time.

If you are using a servo that is drawing a lot of power, even just temporarily, then you may undervolt the entire electronics chain, and actually reset the controller. This would then cause “random movement” in all the servos, as it would wake up, draw power, reset, wake up, draw power, …

Try powering with a high-amperage bench power supply and see how it goes. I’ve found that even 5A may not be enough for the temporary load of some servos – I have to bridge mine to 10A to make sure I don’t suffer from temporary undervolting (this is using a different controller, but the underlying physics is the same :slight_smile:
Also, LiPo cells have a “burst” capacity to deliver a lot of amps, so powering with a LiPo cell might be another way of getting around this problem.

I am using digital park servo 21g to 30g . Turnigy tyg 225-mg.
I still face the same problem. Could it be due to it is a digital servo ??

whenever i connect slowing one by one , after 3rd servo, the servo will go crazy…
The spec say it consume 180MA. X6 pcs which is less than 2 amps.

I wish to isolate and solve the problem.
can i actually power the servo diretly from batteries instead of through the controller ?

or how can i power up 3 servo to 1 source and another 3 servo to another source ?
I also do have 3s or 4s Lipo with regulator (3 A) . which one is a good choice ?

For reference, here is a link to the TGY-255MG: … 12sec.html

Digital servos do not inherently cause problems like this.

What is your Maestro doing with the servo channels as you plug more servos in? What kinds of pulses is it sending? If you disable all the servo channels (stop sending pulses), are you able to plug in all six servos without anything going wrong?

Yes, that is possible, but I don’t think it will help.

You would have to disconnect at least 3 of the servos from the Maestro’s power rail and power those servos directly from a battery. Just make sure that all of your grounds are connected and that you don’t short the positive terminals of two different batteries together.

I don’t know enough about those Lipos to tell you which one is better. Do you know what voltage the regulator outputs?


180 mA is the “running current” on that servo. The “stall current” may be significantly higher. The best way to know is to hook up an amp-meter, or a bench power supply with good read-outs, and measure.

Another option, if you have it, is to hook up a low-cost USB logic analyzer or oscilloscope to the control signals of the servos (if you have one available.)

Finally, servos have three wires in:

  • ground
  • voltage
  • control

The ground needs to be connected to the negative of all your battery packs, as well as your controller.
The voltage could go to any voltage supply – Maestro, or battery, or whatever you want, as long as that voltage supply shares ground with everything else. Just make sure it has the juice to deliver, and that it doesn’t give too much voltage for the servo.

The control hooks up straight to the controller (Maestro.) You may need to use or create some Y cables to be able to make the connections. Just make sure you don’t short your separate power supply to the volt-out from the Maestro!
Pololu sells convenient pre-crimped wires and housings to make your own cables. Get a 50-pack of rainbow 6" male-to-female wires, and a 10-pack of 3x1 housings, and you can make your own cables to match.
(Warning, though: The wires are 26 gauge, so very power hungry servos should not draw their power through these cables, or the insulation will melt. Don’t ask how I know :wink: