View Full Version : permanent 12V
Ascension
12-06-2005, 10:06 PM
Ive got an incar computer hooked up to a touchscreen ive mounted into the dash
http://www.members.optushome.com.au/hyper24/untitled.JPG
The power for the computer comes through a 300 watt inverter, this inverter is hooked up to a relay that is conected to the battery and the acc wire. The acc wire has a switch in it.
So when the key is in and the 12v signal is sent down the acc wire all i have to do is flick the switch i have upfront to turn the comp on.
Now my problem is, if the car is not running but the comp is on, when i go to start the car (crank it) the 12v to the acc line is cut and this turns off my computer.
So all i need is pretty much need is something the same as the acc line but doesnt cut out when the car is being cranked? can anyone help me, thanks.
s_tim_ulate
12-06-2005, 10:23 PM
Try running a relay off another line there. The power is cut to most other parts of the car to give as much cranking amps to the starter as possible. I think the interior light would be on a permanent line???
Splice in at the fusebox into a relay, power the relay off the battery and bobs ur uncle
SmokeyTF
12-06-2005, 10:42 PM
just get a tester and check cables till u find one that doesnt cut when ignition is turned over. shouldnt be hard to find, there is usually a permanent power behind the head unit that constantly runs power to the head unit so that ur radio stations dont get cleared everytime u turn the car off, or on in this case. im pretty sure my TF has one, i assume most would.
the interior light i dont think would run as much power as what u want, unless ur only looking for a remote? and wouldnt the power cut when the light is switched 'off'???
jason
TecoDaN
13-06-2005, 09:13 AM
without having a seperate battery, it will never work the way you intend to do. That is because 300w takes a lot of current. Combine that with the current required by the starter motor, the inverter will just kill itself to prevent power surges to its output.
Ascension
13-06-2005, 11:16 AM
No, the inverter is all good, i had the inverter hooked straight up to the battery and running the comp. I cranked the car and the inverter and computer survived just fine.
But i need to have a swicth up front for the inverter thats why theres a relay with the acc line hooked up.
When i crank the car, the remote line to the relay turns off, so this cuts the power line to my inverter.
all im looking for is a PERMAMENT 12V LINE, NOT POWER, JUST REMOTE! so when i crank my car, the relay stays closed and the power stays to the inverter.
I read somewhere its the IGNITION wire out of the key barrel, does anyone know the colour?
Also is it safe to use a hardline straight from the battery as a remote line? thanks.
Gerard
13-06-2005, 08:17 PM
what about a uninterruptible power supply thing? that'll do the job aswell.. its what i was thinking about using..
i never knew there was a permanent 12v supply in the car..
s_tim_ulate
13-06-2005, 08:33 PM
headunit for instance has permanent 12 v to store it with settings which are lost on full power down.
Interior light, engine CPU, etc
Gerard
13-06-2005, 08:39 PM
hedadunit has permanent 12v?? mine doesnt... same with interior light and everything else.. as far as i know.. it cuts off for a second when i start the engine, always has, i think hu's have a small cap in there to store small amount of charge to allow for the engine startin up. It takes me about 5 minutes of disconnected battery for it to reset.
maybe its a 3rd gen thing?
M4DDOG
13-06-2005, 09:57 PM
Just hook it up straight from the battery to a fuse, then to a switch.
Gemini
14-06-2005, 09:19 AM
http://www.mp3car.com/vbulletin/ is a forum dedicated to car computer installs. I am sure they have a solution to this problem :)
BTW you should see some of their installs they are awsome :shock:
Ascension
14-06-2005, 09:35 AM
im apart of that forum already, where do you think i got all my help from.
Im using the xenarc 7" screen from that site!
ZachTS
14-06-2005, 05:07 PM
without having a seperate battery, it will never work the way you intend to do. That is because 300w takes a lot of current. Combine that with the current required by the starter motor, the inverter will just kill itself to prevent power surges to its output.
300w and the currant it draws are completly different things. a standard computer power supply wont draw anymore than 10amps and the fuse in the inverter shouldnt be anymore that say 15a.
nothing in your house draws more than 10a.
for an incar computer you would ideally use a 'mini itx' main board and the 12v power supply associated with it.
the specifications for 'mini itx' state that the whole mainboard must be smaller than
17cm x 17cm which makes that one really small computer.. these boards come in different configurations, but expect to find one with dual 1000mb network cards, at least 32mb video (if not shared up to what ever level u choose) and usually 5.1ch audio.
the boards are intended for use in computers that are built for multimedia purposes, home entertainment units are one example... you can buy cases for these boards that look just like a dvd player.
'micro itx' main boards are a totally different kettle of fish.
well not really, the main differenace in that their size specification is under 10cm x 10cm...
and that kinda size can nearly fit into a single din space.. so with a 7", in dash touchscreen you can have a double din unit that does the lot!
if you want to design your own windows interface for in your car check out Media Engine.
if you want more info on any thing i've mentioned, pm me or email me and i'll send you some links.
Zach
ZachTS
14-06-2005, 05:10 PM
hedadunit has permanent 12v?? mine doesnt... same with interior light and everything else.. as far as i know.. it cuts off for a second when i start the engine, always has, i think hu's have a small cap in there to store small amount of charge to allow for the engine startin up. It takes me about 5 minutes of disconnected battery for it to reset.
maybe its a 3rd gen thing?
all headunits have:
- a constant power (yellow wire on aftermarket decks)
- an accessories power (red wire)
- an earth (black wire) NOTE: some OEM units earth themselves via their chassis or antenna.
just thought i would clear this up.. all magnas have an acc and constant wire behind the decks.
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