Problem while connecting the Arduino to external power supply AND USB for interf

Other Hardware Science and Measurement
1

Hello,

I am having aproblem while connecting my arduino to both an external power suplly and the USB and I cannot figure out the solution. My set-up is as follows:

I am using an ATX power supply in combination with a voltage regulator as external power supply, because one of of my pressure sensors uses a 24V input I've connected the -12V and +12V of the ATX to my voltage regulator and set the voltage regulator to produce 7.5V, which is an acceptable voltage for the Arduino. Now all goes well, I can read the sensor output using an LCD display, but the second step is that I want to connect and monitor the output from the arduino with Matlab Simulink. Now when I connect the USB to my computer and I use the external power supply simultaneously the ATX shuts down.

My question is why does this happen? And more important, how can I solve this problem? Any help is very much appreciated.

2

does the computer and the Arduino share the power supply?

Can you make a drawing and post that please?

3

Hi,

I don't have the possibility to make a sketch, but here is some more information, I made the power supply for the Arduino similar to this power supply:

Then I made a second circuit similar to this one:

I connected the -12V and the +12V to the input of the regulator and adjusted the regulator so that it gives a nice 7.5V to the arduino. All works fine untill I connect the USB to the computer, then the ATX power supply shuts down.

Maybe it has got something to do with the power resistor of the ATX power supply being connected to the 0V and +5V?