I have a DMX controller using a 3 pin connector (gnd, data+ and data-). I need to connect it to some cheap chinese DMX lights. The problem is that the lights are powered over the same 3 lines using a 24 VDC power supply. When I did, it burned out my controller. DMX is a differential signal, so it might work, but 24V is just to much (and clearly out of specs of DMX standard, which allow for at most 7 volt). These are the lights so there would be no problem with other DMX lights. The 24 DC power is connected to gnd (pin 1) and data+ (pin 3) of the DMX ights and is needed to power the lights.
As extra info, my DMX controller is running on the power of a usb port. When using a multimeter in AC mode (with the lights and 24V disconnected) It measures 2.5-3V on the data channel, while it is sending out some data.
How to prevent my new (expensive) controller to burn out as well? (it shouldn't see the 24V)