Micro Maestro turned off after switching an ext. appliance


i suspect my issue is similar to the previous post : https://forum.pololu.com/t/micro-maestro-is-turning-off/3541/1

Basically, when i switch on/off an external appliance, it had affected my micro maestro to turn off itself and stops receiving commands from my laptop.

My current power setup is as follows:
My servo power is connected to a wall wart 5V 1A.
micro maestro is powered by a laptop USB, which the laptop is powered the mains.(not battery).
My external appliance is an industrial type fan connected to the mains.

The fan is by no way connected to both the laptop and maestro. But when i switch on/off the fan, the servos connected to the maestro jitters and most of the time it turns off the maestro (green LED not lighting or blinking, and maestro control center is giving me "Error code 0x1f ").

To solve the issue manually, i have to close my program using the port , and re-plugin the usb for it to resume normal operation.

My exhibition requires the setup to be sustainable for long periods, without much manual attention to remedy the issue. The fan would be on and off frequently too.

Is there a way to prevent this to happen?

I was thinking if i modify my program send soft reset commands to the maestro when this happens, or can i even attach a battery to power maestro by connecting to Vin while attaching the usb(hopefully it will keep the maestro on)?

I have tried other appliances like lights and it does not seem to affect much. But the fan still affects the maestro, probably it had a current spike along the mains, which affected my wall warts and laptop as well.


Hello, cpoohee.

I’m sorry that you are having trouble with the Maestro.

What kind of program did you write to control the Maestro? Does it use the native USB interface or the virtual COM port?

What operating system are you using? If it is a version of Windows, is the Maestro visible at all in your computer’s Device Manager when it is in this bad state?

In the Maestro Control Center, in the Serial Settings tab, could you please try checking “Never sleep (ignore USB suspend)” and see if that changes the behavior of the LEDs on Maestro? This should tell us whether power is being delivered to the USB port while the system is in this bad state.


thanks for fast response,

i wrote in MS visual 2010 C++ , using virtual com port , with your codes from a prev post :https://forum.pololu.com/t/maestro-c-serial-communication/3181/5 :slight_smile:

I’m currently out of the workplace which my maestro is at. But i will try to recall what i can remember. Earliest i can verify again will be on coming Monday.

Its running on win xp SP3, i have not checked the device manager before, but i can remember there is no “disconnected USB” sound when this issue happened. Only when i physically re-plugin the usb, the “disconnected USB” sounds followed by “UBS device detected” sound.

I cannot verify the current state now, but if i can remember, i did checked “Never sleep (ignore USB suspend)”, applied the settings, and unchecked the device manager->(all) USB Root Host-> power management settings.
The Yellow LED was lighted, but i cant remember it in a flashing state or lighted state. The green LED was off. No red LED too.
No error message on control center, until an exception when try to send commands from the slider bars.

When running my program, with this bad state, the printed message was “Error: Unable to write Set Target command to serial port. Error code… (sorry, i cant remember)” , which means the writeFile() from the “maestroSetTarget()” had returned false.

i hope i can programmatically resolve the issue. maybe by making use of the error message detected. i don’t mind if i have to add additional hardware to sustain the maestro, or do something about the fan. Any suggestions would be appreciated.


Hello, cpoohee.

I would try putting a powered USB hub between the Maestro and the laptop. If you have an unpowered hub you could try that too. I don’t know exactly what is happening in your system, but I think that an electrical disturbance of some kind is happening and when you computer detects it, it shuts off USB communication with the Maestro. A powered USB hub might be more resilient and protect the computer from whatever is happening on the Maestro’s side.

I hope this helps!


Hello, PooHee. You haven’t written back in a while. Were you able to solve your problem? What was the solution? --David