Can the HD 1501MG servo be modified to turn 180 deg?


Does anyone know what is the stock rotation range of the HD 1501MG servo? And does anyone know if it can be modified to turn 180 degrees?


I bought a couple of these servos. The torque is great. With pulse widths of 1 ms to 2 ms, the servos rotate 90 degrees. However, if I manually turn the output shaft, they rotate 180 degrees. Does anyone know how to modify these servos to increase it’s range from 90 degrees to 180 degrees? Thanks. --Osman


On most servos, you can get a range beyond 90 degrees by sending pulses outside of the standard 1-2ms range, which is a feature of some servo controllers (including our Maestro Servo Controllers). Be careful not to push the servo too hard against its limits of its motion, or it could destroy itself. I usually start with the lowest possible supply voltage (3 or 4 volts) and gradually move the servo toward each end until I find the limit point. Then I back it off a bit and configure my controller to never go past the limit.


Did you come right?

I would like to do the same with my 1501MG Power HD servo… I bought them thinking they are 180 degrees… It’s so hard to find proper datasheets for servos.

Is it possible to make it rotate 180 degrees when its supposed to be 90 degrees… when i manually turn the servo it can go to 180 degrees.


Hopefully Osman can let us know if he got it to work with an 180 degree range. Since you have one though, you should be able to test it yourself. We have a FAQ about exploring servo range limits on the Masetro controller product pages. Look for the FAQ titled “How do I use my Maestro servo controller to get the maximum possible range of motion from my servo?”.

- Ryan

If it helps, I used some 1501MG servos in a project recently and was able to get one to turn close to 180 degrees with a Maestro. I didn’t measure the rotation range precisely, but it was probably at least 160 degrees.

- Kevin

Okay awesome, I will have a look at that maestro then! Thanks

So, I managed to get it to rotate more than 90 degrees :mrgreen:

Here is how:

  1. It operated at a frequency of 300Hz
  2. Vcc = 4.5-6V
  3. Current = 1.2-1.5A
  4. Vin = Square wave with peak-peak @ 1.5 - 6V
  5. Max Duty Cycle on = 2.56ms
  6. Min Duty Cycle on = 1.64ms

The main reason it was only rotating 90 degrees is the current was too low!
Hope this helps other people as there is little information out there on servos.

I’m glad you got something working. I don’t know what you mean when you say you have a square wave on Vin. Generally, we do not recommend a varying voltage for your power supply.

- Ryan

With a square wave on Vin I mean the input signal… Vcc and GND are for the power, and Vin is for the input signal :slight_smile:

Vin is usually used to represent the voltage input connection for power, so using that to represent the signal can be confusing. I usually call it Signal or Sig for short.

- Ryan


Is there a servo with similar torque and speed that can turn 180 degrees? For my project I need exactly 180 degrees of rotation. Thank you!

Hello, taltmann.

Sorry for the delay in replying. Generally it is hard to answer your question. The explanation for why it is hard to answer can be found in the second FAQ found on any of our servo pages titled “How many degrees can this servo turn? Why do you not list it with the other specifications?”. The best way to do it is buy a couple of different servos and try them out.

- Ryan

Another alternative is to buy servos that are explicitly rated for wider rotational ranges. Some digital servos are, as well as hobby robotics servos.
You will end up paying more, though, and for the case of hobby robotics servos, will need another kind of controller than a hobby PWM controller (typically, single-ended TTL.)

Some links: … tuator.htm

Note that all these servos have bottom-end idler horn mounting holes, which is important for robustness in applications where the spline will see any kind of shear/axial load rather than just twist load.