Strange problem with usb host shield and high voltage servo

Hello,

I am experiencing a problem with an Arduino UNO with the USB host shield from circuits@home and a 7V servo. I use an external power source to get the 7V for the servo. I also connect a PS3 controller with a USB cable to the host shield and use the PS3USB example from the library. Everything works fine, if I do not connect the power adpater to get the servo working, that is, I see the PS3 controller working, I see the values from the buttons in the serial monitor. But when I connect the 7V adapter, the arduino hungs and I cannot get any positive behaviour. The serial communications don’t work and the PS3 controller doesn’t seem to work either.
I connect the 7V directly to the servo and the Arduino power input.
I am completely stuck. Any idea of what the problem could be?

Thank you very much
Rafael Caballos

Hi, Have you got the gnd of the servo power supply connected to the arduino?

Tom... :)

Yes, I keep the same GND for all the devices. From the power supply, I connect the GND and 7V wires to the Arduino power connector, and also to the servo connector, together with the PWM pin, precisely D7 pin but I think it should be the same if different.

Regards Rafael

Something I forgot to mention before. What shocks me is that evertything seems to work with the power supply off. The same moment I switch it on, Arduino hungs, even the IDE on my PC. I tried to use the USB power to work with Arduino instead the 7V supply, but if I turn it on to make the servo work (it does not work with 5V) then hungs. And at this moment, the 7V wire only touches the servo. I guess that something related to USB communications is affected by the power supply, but don't know what or why. And by the way, if I do not use the USB host shield, everything works without problem, but I need the PS3 controller to move the servo in my project.

Regards Rafael

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Tom... :)

Hello,

I attach a picture. Sorry for the bad quality. It is the best I could do with Paint.

Regards
Rafael

Hi,
What is your 7V supply and where on the arduino do you have it connected?

Tom… :slight_smile:

Hi,

The power supply is a high power one bought in Internet. I attach a picture. I connect it to the power jack in the arduino. If I do not use it and use USB instead, I also connect a GND wire from the power supply to a GND pin in Arduino.

Regards
Rafael

supply.jpg

The power supply is a high power one bought in Internet. I attach a picture. I connect it to the power jack in the arduino.

When the power supply is connected to the arduino, what is the voltage on the arduino 5v pin?