to control my amps i use pin 4 of my serial port and the service that raises power on that pin when pc is turned on.
this works all very well, but now i want to connect a relais to pin 4, so i can use a regulated 12v to switch on my amps (instead of the 10.7v pin4 is giving me)
anyway, when i want to do this, i'm gonna need more then just pin 4 (also a ground), but when i use a ground and pin 4 to close the relais, all works fine, but when i turn off my pc, pin 4 gives me -12v instead of 0v, turning the relais back on...
is there a way to avoid this? so, either way have 0v on pin 4, or make my relais not turn on when there is -12v on it?
Hint : A diode will prevent current flowing backwards.
Old Systems retired due to new car
New system at design/prototype stage on BeagleBoard.
so soldering a diode between dtr and the relais would fix my problem? (i'm really a noob in this) or do i need 2 diodes (1 between dtr and the relais, and the other between the relais and the ground, and switch the second one around)?
and can a normal diode handle the amperes coming from the serial port?