Three position switch for white (accessory) lead?

Jistari · 03-14-2008, 05:48 PM

Any reason I couldnt place a switch on the white and red leads before the pc in the car that would have three positions as follows :

Pos 1 : Red passes through white passes through
(would act exactly as it does without the switch, power on white line signals pc to start up when car is started and shut down when car shut down)

Pos 2 : Red passes through white interrupted
(would shut power on white lead, could be used to restart pc through psu seeing white interrupted, or if left in this position would prevent pc from starting when car starts)

Pos 3 : Red passes through on red line and is also connected to white lead
(bear with me on this)
(this would be used in the case when the car and pc are running, and you want to shut the car off but keep the pc running)

Yup, I realize pos 3 would drain the battery, and I aslo realize you can set the MTX 3 to do this for a programmable amount of time, but I think I might prefer to have the M3 set as I have it (start in 5 seconds and shut down in thirty seconds) most of the time, I would just use pos 3 occaisionaly when I want to stop for a few minutes, but dont want the pc to shut down.

So, ignoring my thickheadedness, just on a factual level, is this a simple thing to wire up? I have a three position switch but havent tried it yet, not sure if I have the right one.

I'm guessing I will have to:

Leave the red line alone

Have one side power the white line from accessory fuse (like it is wired now)

Have the other side power the white line from the red line

And when the switch is in the middle position, have white disconnected

That work?

FusionFanatic · 03-16-2008, 07:57 AM

what are these red and white "lines" connected to? is one of them power and one ACC / IGN?

it's hard to figure out if it will work when you don't say what the red and white wires are.

Jistari · 03-18-2008, 03:21 AM

Dont know what I was thinking, I usualy over explain.

Sorry, yes, red is positive from a fuse tap on a 20 amp fuse that is always powered and white is positive from a fuse tap on a 20 amp fuse that is only powered when the ignition is on.

Jistari · 03-20-2008, 12:30 AM

Kill this.

Works great the way I described.

a2carat · 06-09-2008, 06:20 PM

Im trying to do the same thing... and was planing doing the same thing you did but I have a question... if I have the car runnig (carpc is on) and I want to Leave it on.. so I move the switch from position 1 to position 3 the carpc its going to think the power button was press since I have to go through pos 2 am i correct?

thanks
Felix

tigergibb · 06-09-2008, 08:29 PM

You want a "SPDT Center-Off" switch. Here's how mine is setup:

Switch Position
Up: CarPC On (12V connects to white)
Middle: CarPC Off (Center is off, so nothing is connected to white, thus CarPC off)
Down: CarPC turns on/off with car IGN (IGN connects to white)

And here's the one I have:
http://www.allelectronics.com/make-a...WITCH/-/1.html

Here's other switches from them that should work too:
http://www.allelectronics.com/make-a...-SWITCH/1.html
http://www.allelectronics.com/make-a...DIODE/-/1.html
http://www.allelectronics.com/make-a...-HANDLE/1.html

If I'm leaving for 5-15 minutes to go in the store or something I just flip the switch up so the computer is still on when I get back. If I am just moving the car in the driveway and don't want the computer to come on I put the switch in the middle position for off. Any other time the switch is down so the computer turns on/off with the vehicle.

FusionFanatic · 06-09-2008, 09:16 PM

Quote: Originally Posted by a2carat

Im trying to do the same thing... and was planing doing the same thing you did

here are some diagrams I made to help another member. maybe it will help you too

the diagrams show an M2-ATX, but the wiring will be the same for any PSU with a turn-on/trigger wire.

this one is for a simple override switch. it uses a 3-lead SPDT (center-off) switch.

this one is the same thing, but includes an LED to indicate when the switch is in position#3 (always-on). it uses a 6-lead DPDT (center-off) switch.

Quote: Originally Posted by a2carat

I have a question... if I have the car runnig (carpc is on) and I want to Leave it on.. so I move the switch from position 1 to position 3 the carpc its going to think the power button was press since I have to go through pos 2 am i correct?

you would be correct if the PSU reacted that quickly, but it probably won't (the M2-ATX doesn't

). with a center-off toggle switch you can switch it fast enough (from #1 to #3, or vise-versa) that the PSU will not even know you switched it.

good luck

a2carat · 06-09-2008, 11:41 PM

Thank you both

I think im going to wire that led too, because I want to hide the switch but at the same time put it somewhere easy to get to, in other words not visible, making it also like a valet switch

Thanks again

Felix