Maestro 12 - servo position range issue

Hi, first time using maestro, so please correct me if I’m doing something wrong. I have a futaba servo connected, which I believe has a 270 degree range. I connected wires and 5v power supply. I can move the servo using pololu software but my range for position when sevo moves is very small. I changed min/max to 200/4000, or others, but seems like my servo does a complete right turn around 1450 (1440 was midpoint) and does a complete left turn at 1430. I used all speed/acceleration setting changed min max but servo moves within a very small position range. What am I doing wrong?


Can you post some pictures of your setup, a datasheet for your servo (or a link to where you got it), and your Maestro’s settings file? You can save your settings file from the Maestro control center under the “File” menu.

- Patrick

Ok, attaching pictures and screenshots. I had another similar motor so I attached that too and it seems like it’s a full rotary /continuous rotation servo, and that also moves clockwise or counterclockwise within a short range. I don’t know if that’s the intended behavior? I have a flaps gauge for flight simulator that needs to go to 5-6 flap levels, approx 30-35 degrees apart.
Really appreciate your help.

I cannot access your Google drive folder, so can you adjust the sharing settings or post your files directly to the forum?

- Patrick

I apologize, I changed permissions so you should be able to see.

What is your power supply for your servo, and what is the servo’s mechanical range when you power it off and turn it manually? Do you have some other way to test your servo, like an RC receiver, or have any servos you know to be working that you could test with the Maestro? Also, if you have an oscilloscope (or if you can borrow one), could you take a look at the Maestro signals to confirm that is working correctly?

- Patrick

I’m using 5v power supply from a PSU, I have vin/vsrv jumper enabled as well. I connected another servo, which moves fine with my Opencockpit servo card, but same thing after connecting to polulu (I had to reshuffle power and signal wire as Opencockpit wiring is different) I created two videos of how servos dont move (the new one) or move within a short position range, both videos are in the same google drive. Please let me know if I’m doing anything wrong.

The reason I want to use polulu is it is supported by default with prosim-ar software, where for Opencockpit I have to write some scripting. I don’t know what an oscilloscope is.

Thank you for posting those videos. Please note, our company name is Pololu, not “polulu”.

Is the last servo you mentioned one of the ones in your videos (which I am presuming correspond to the servos you mentioned in your first two posts), or is this a third servo?

Right now my leading suspicion is that the servos you tested in your videos are somehow damaged. That would explain why you can hear them trying to move, but they do not actually move. One way they might have been damaged is if you commanded them to a position beyond their physical range, such as when you increased the min/max position to 200/4000μs, which is way greater than the range of most hobby servos.

Can you try testing the same servos from your videos with this Opencockpit servo card you have and tell me if and how they behave differently? I recommend you take the servos out of your simulator to do this and for further troubleshooting to make it is easier to see what is going on at all times.

Also, I am still not certain how your servos should be behaving (e.g. if your second servo is really a continuous rotation servo, then it should never reach a stop point if you command it to move a particular direction, no matter what the specific pulse width is). So, with the servos unpowered can you check what their range is by carefully moving them manually? You can also use this as an opportunity to feel for any signs of mechanical damage.

An oscilloscope is an electronic test instrument that graphically displays signal voltages and how they change. For example, you could use a scope to observe servo control signals which occur on the scale of microseconds. You can get a decent scope these days for a few hundred dollars, so we strongly recommend investing in one. It will save you a lot of time and give you better understanding of your systems, which enables better designs, better margins of operation, etc. Without one, you are left mostly just guessing about what might be happening, which is not a great way to operate.

- Patrick

I apologize for the spelling mishap, my phone keeps correcting to the wrong spelling. I’ll watch out next time.

So the 2nd servo in the video was actually 3rd servo, after making the video, I reconnected it back to opencockpit and everything was working fine (And luckily wasn’t damaged but I’ll keep the range comment in mind for next time) (Opencockpit only have range of 0 to 1023 set up as default). If I select this range in Pololu, it doesn’t move a bit.

I’m starting to believe it might be the card, I’ll order a replacement to see if it helps, so I’ll let you know.

This would be an unusual failure mode for the Maestro, so I am still suspecting a problem elsewhere. Can you post your Maestro’s settings file?

It is getting increasingly difficult to keep track of everything, so for each of the three servos you have been testing with can you tell me:

  1. Its range when you move it manually (as well as if you notice any mechanical problems when you move it)
  2. Its behavior using the Maestro Control Center using default settings
  3. Its behavior using the Opencockpit board

Also, when you test your servos with the Opencockpit board, are you using the same power supply as when you test them with the Maestro?

By the way, the control signal values in your Opencockpit interface and the Maestro Control Center are not equivalent. It sounds like Opencockpit is just setting a pulse width based on a ten-bit value, whereas the Maestro Control Center interface allows you to enter the actual pulse width in microseconds. However, if you have some documentation for your Opencockpit board that indicates what range of pulse widths that ten-bit value corresponds to, please let me know since that might be useful.

- Patrick