Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Mini Maestro 12 channel powering problem

I am using 12ch Maestro and my primary goal is to control servos wireless using Bluetooth modem from Sparkfun. I have connected my 5V power (Lipo battery via voltage regulator to give 5V output) to maestro GND and VIN pins. Bluetooth modem is connected to Maestro BAT pins and VSR=VIN is on. Maestro Rx and BTModem TX are also connected. One servo is attached. When the power is on, BTModem starts working as expected, but Maestro seems to be dead, I think the yellow led should be flashing. My software connects to the BTModem but no servo movement.
Then when I attach the USB cable from PC green led is on and yellow starts flashing. Now I can control servos via TTL and BTModem and also via USB and Maestro Control Center.
Maestro 5V pin in the center has about 2V voltage.
The power seems to be sufficient to the BTModem and servos but not for the Maestro ?
So how can I get it working without USB cable attached ?


Can you please post some pictures of your setup and provide more information about your LiPo battery and boost regulator? Can you try disconnecting everything from the Maestro (Bluetooth modem, servos, USB cable, etc) and then attempt to power the Maestro by connecting your power supply to VIN and GND? Could you tell me what you measure on VIN both before and after connecting it to your Maestro?


I connected the power supply straight to GND and VIN connectors, but the Maestro is still dead.
Unfortunately due to short circuit I managed to burn the connection between VIN and VSR. However the Maestro is still fully functional if it is powered via USB and the servos (and BTModem) get power separately.
So I think the connection between VIN and Maestro is broken (damaged).
So my question: is it possible to power the Maestro any other way than USB and PC?
I could break an USB cable and try solder those ultra thin wires, but maybe this would be an unreliable powering in the long run ?

Unfortunately, there are not any other options for powering the Maestro. In case you missed it though, there are two VIN pins, so if you damaged the VIN pin by the VSR rail, then you might try powering the Maestro through the VIN pin near the USB connector.

If that does not work, could you post pictures of your board and tell me more about this short circuit that damaged your VIN and VSR connection?


Hi !
The VIN connector near USB is not working. I think that that maestro gets power (VIN) via internal voltage regulator. That requlator is damaged. When the maestro is powered via USB, it does not go through regulator, is that true ?
So I made “USB power” from USB adapter as seen in the following pictures. The regulated 5V power is connected to holes between the two 6-piece servo connectors. USB-power is connected to 11 ch servo and Bluetooth modem to BAT connectors. This way maestro seems to be working normally.
By the way, are there any plans to replace the maestro (old fashioned) mini USB connector with micro USB ? Would be much easier to find cables…


There is still one thing I cannot understand here. If I connect the power via USB with setting like this and no servos are connected, the yellow starts blinking and the maestro is on. When I then connect one servo, I can control it normally.
But when that servo is already connected and I switch the power on, the yellow led blink twice shortly and is then off and maestro is dead.
Measuring the voltage in usb connector : 5V, so how much power the maestro really needs ?
My power supply is capable of giving power to maestro, BTModem and servo when servo connection is initially off


When the Maestro is powered via USB, it bypasses the regulator, so it seems like the regulator on your Maestro has been damaged.

At some point we will probably make a successor to the Maestros that uses a Micro USB connector, but we do not have a time frame for that, and we do not have any plans for remaking the current Maestros with a different connector.

It sounds like your Maestro controller could be browning out when the servo is connected; are you powering the Maestro and the servo from the same supply? If you are, then you might consider powering them from separate power supplies to avoid that. Can you look at what your power input is doing on an oscilloscope?