Where can I get a constant -12v?

[Spare-Flair]

This is the mod I made and posted in the case modding forum a month ago with a car security LED scanner, but everytime I turn off the computer, the led board will reset itself to an ugly pattern and I have to open up the case to change it back to scanner mode.

Right now I have the red +12v wire from the device plugged into the +12v yellow wire from a molex cable. The device has a black ground and a white negative. I've plugged both into the grounds of the molex. I think I need to connect the white negative to a constant powersource so that it doens't forget it's memory settings everything I swtch off.

Okay, so bought a LED scanner designed for car security systems and since it was 12v, I decided to hook it up into my system. It has 8 different LED patterns but I chose the back and forth scanner sweeping mode like KITT or a Cylon helmet.

I'm generally the type of guy who hates flashing lights and other things about case mods, I don't even have a window, but I've always preferred the insides of a computer to be more of a mystery with some hints of inner workings and some touches of sci-fi. The scanner also goes with the red motif of my case LEDs and interior.

I installed the scanner behind an aluminum intake grill that I got off a server case and installed into a 5 1/4" bay and put a filter behind it which diffuses the light from the scanner so it looks like it's the inside of the computer. I just stripped an old molex connector and spliced in the wires from the scanner. It looks better in person and in the dark than in pictures or video. The light is much more defused and the pattern of holes in the grill make it appear that it's ghosting. The video doesn't do it justice.

This video isn't the best quality and it's also bright which takes away the effect (best when the lights are off but my camera doesn't workin low light).
Scanner Video (Divx Low-Motion) 700kb

 

[jpmkm]

I really doubt you need -12VDC since no regular car has that.

 

[PretendR]

most of the time if you need a electronic circuit to remember a sertain function you use a memmory chip (eprom eeprom etc) . in a car most of the time they connect te electronic circuit directly to the battery from the car (only with a fuse in the powerlines) so the circuit won't be reset. in the computer you cant use these kind of electronics cause you dont have a battery. Try a different circuit that only has that function.

 

[ProphetSix]

Just a thought, but could you wire it up to use a 120V to 12V "wall-wart", and run the line in the case, and hook it up to use building power when the PC is off, and PC power when you turn the comp on? Someone else might be able to help with the circuit design, but that would give you a constant 12V source.

 

[Harlequin]

I don't know how the circuit operates, so I don't know if this is a useful solution, but you could put a memory capacitor on the chip that generates the patterns. Chips don't need much to keep their state when they're not driving other logic devices, so providing the cap just feeds the chip (a big if - it depends on the circuit design) that's an option.

Otherwise, perhaps look into using the standby power from the PSU - not 12V, but the chips don't need 12V to maintain their state.

Otherwise, get a regulated 12V wall adaptor and wire it to the power socket in your computer?

 

[Spare-Flair]

I don't know how the circuit operates, so I don't know if this is a useful solution, but you could put a memory capacitor on the chip that generates the patterns. Chips don't need much to keep their state when they're not driving other logic devices, so providing the cap just feeds the chip (a big if - it depends on the circuit design) that's an option.

Otherwise, perhaps look into using the standby power from the PSU - not 12V, but the chips don't need 12V to maintain their state.

Otherwise, get a regulated 12V wall adaptor and wire it to the power socket in your computer?

-5V? Wire it off the main PSU power connector?

 

[theshadow27]

Two options not already mentioned…

Step up converter from 5v to 12v to run it off the stby power that is in the ATX mobo connector.

Put a small 12v gel cell battery in the bottom of your computer (like for alarm systems/UPS boxes) and wire it up to that. It would charge when the computer was on (right off the 12v) and with a diode only run the display when the computer is off

Best of luck
//theshadow