Micro Serial Servo Controller and USB to Serial Adapter

Can the micro serial servo controller be powered from the USB port? I will power the servos from an external souorce, but can the controller itself be powered from the USB port? if so, would I just use the Vbus out of the USB to Serial adapter?

Thank you :]

Yes (you can power the micro serial servo controller from the USB to Serial adapter) and yes (you would use the VBus pin on the adapter for +5V power for the controller, but not for the servos).


Thank You adam,

So I will connect Vbus form the USB adapter to VIN on the servo controller. Do I need to connect the GND from of the USB adapter to both ground pins on the servo controller (the VIN GND and the RS232 GND)? I would assume they are common, but not really sure what is the best thing to do.

Thanks Again

All grounds are common on the micro serial servo controller, so you only need to make one ground connection. The ground pin right next to the Vin pin is probably the easiest place.


thanks again.

Well it’s all hooked up, so let the problems begin. I am trying to use the pololu servo example software.

When i first plug in everything, the tree lights remain on. I wait but they stay the same. When i send a command from the software, I just get the solid red light “fatal error”

then I try the serial transmitter software, and just send 0x80. i get nothing but baud speed errors ( from the flashing lights.

The usb software seems to have installed well, and assigns com5 to the adapter.

any suggestions?

here is my wiring:

usb ----------- servo control

GND -------> GND
TX ---------> RS-232 Serial Input
Vbus ---------> VIN

Just to be clear, are you using the Pololu USB to Serial adapter (this guy)?

It sounds like you are, and your current wiring would cause exactly the problems you describe. The Pololu USB to Serial adapter outputs TTL level serial signals, so you would want to connect the adapter’s TX line to the servo controller’s SIN pin.


yes adam, that is the correct usb adapter. So need to connect it to the “logic level serial input” pin on the control board pololu.com/catalog/product/207 (the pin next to the VIN pin)? Thank you for your help.

Oh one more thing, you said all of the grounds are common, but I have read elsewhere that I need to make a jumper between the servo power ground and the controller board ground because I am using an external battery. Is ths not so?

Thank You,

The ground side of the servo power bus on the servo controller board is connected to the logic ground pin.

The normal way to power the servo motors is to hook up a separate battery or power source (usually 4V to 6V) to the servo power pins. This conducts power to the servos through large traces on the servo controller circuit board. If you are using very large servos that draw a lot of current, you may want to bypass the controller board and connect power and ground to the servos through wires, and running individual signal wires to the servos. If you do this, you still need to connect the ground side of your servo power source to the servo controller board. Unless you have giant super-torque servos you probably don’t need to do this.


Success! Everything works now that I have used the correct Rx pin. Thank you for your help.