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07-28-2009, 05:25 AM
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#1
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Newbie
Join Date: Mar 2009
Posts: 13
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NooB Question about powering a laptop using M2-ATX
Hi All,
I am planning to gear up my own Carputer using my old Acer Laptop.
I have been searching and reading a lot of forum posts for my question.
I found many people placing laptops for carpcs and they have excellent solutions for auto power up / shutdown.
From what all i have learned till now i have tried to put up a design to power my laptop, screen and devices
I will be using M2-ATX (instead of CarNetix 1900) incase my laptop dies and i have to switch to a PC.
Question i have is
When i power down Ignition of my car, the laptop will still be connected to the Car battery from M2-ATX. Thus laptop will continuously draw power from car battery to charge laptop battery. Wont it kill my car battery?
Or M2-ATX cuts the power to the laptop when ignition is cut off.
Consider me a total noob in powering 
Thanks a lot
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07-28-2009, 05:31 AM
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#2
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Low Bitrate
Join Date: Dec 2006
Posts: 90
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Unless you have a notebook which charges/works from 12V, M2ATX will not be able to power it. Most laptops which I'm aware requires and input of 19V which M2ATX is not designed to generate.
Carnetix 1900 is your best bet if you are using a laptop. If you are on a budget, a Car adapter for the laptop may be a good deal but it would be limited when compared to Carnetix 1900
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07-28-2009, 05:46 AM
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#3
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Newbie
Join Date: Mar 2009
Posts: 13
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Quote: Originally Posted by DigitalVampire  Unless you have a notebook which charges/works from 12V, M2ATX will not be able to power it. Most laptops which I'm aware requires and input of 19V which M2ATX is not designed to generate.
That is why i am adding a 12v-19v DC Car Adapter for Laptop
Quote: Originally Posted by DigitalVampire Carnetix 1900 is your best bet if you are using a laptop. If you are on a budget, a Car adapter for the laptop may be a good deal but it would be limited when compared to Carnetix 1900
If i use only Car Adapter then what about the power that laptop will keep drawing from car battery even after powering down the ignition.
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07-28-2009, 06:03 AM
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#4
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,910
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Quote: Originally Posted by compuwengo If i use only Car Adapter then what about the power that laptop will keep drawing from car battery even after powering down the ignition.
Wire it to an ignition-controlled circuit so the power to the car turns off with the ignition.
You can do the same thing with a relay, as well.
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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07-28-2009, 06:09 AM
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#5
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Newbie
Join Date: Mar 2009
Posts: 13
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Thanks DarquePervert,
In case i power my laptop to Ignition Controlled circuit, then also i would need power for my devices. Can i power my other devices (LCD, SoundCard, etc) also from Ignition Controlled Circuit?
More over in that case, i guess, i would need a SSC for controlling startup and shutdown.
Please tell me will it work if i put in a Car Adapter ahead of M2-ATX as in my design?
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07-28-2009, 10:49 AM
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#6
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Constant Bitrate
Join Date: May 2008
Posts: 173
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The M2-ATX will hard-off the 12v line after a preset amount of time depending on how you set J10.
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07-28-2009, 10:53 AM
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#7
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,910
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Quote: Originally Posted by Sicarius The M2-ATX will hard-off the 12v line after a preset amount of time depending on how you set J10.
The M2ATX is completely unnecessary for a laptop install.
You completely missed the boat.
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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07-28-2009, 11:06 AM
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#8
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Newbie
Join Date: Mar 2009
Posts: 13
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@Sicarius : Thanks, you answered my question
@DarquePervert : I would love to know more, Let me know how would i power my other devices.
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07-28-2009, 11:13 AM
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#9
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Newbie
Join Date: Mar 2009
Posts: 13
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I think DarquePervert is pointing towards something like this.
In this case what about other devices? Other 12v and 5v Devices. Should i power all to Ignition Controlled Ckt?
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07-28-2009, 12:22 PM
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#10
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Low Bitrate
Join Date: Dec 2006
Posts: 90
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Quote: Originally Posted by compuwengo That is why i am adding a 12v-19v DC Car Adapter for Laptop
I totally missed your wiring diagram. My office firewall filters all image attachments.
Now that I'm home, I see your wiring diagram, but still believe it is a very inefficient setup and adds to the cost. 2 DC-DC converters in series!!!
Quote: Originally Posted by compuwengo I think DarquePervert is pointing towards something like this.
In this case what about other devices? Other 12v and 5v Devices. Should i power all to Ignition Controlled Ckt?
This looks good as long as your screen is tolerant to voltages upto 14.4V or sometimes even higher. I'd add a 12V regulator for the screen to be on the safe side
Last edited by DigitalVampire; 07-28-2009 at 12:43 PM.
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07-28-2009, 12:25 PM
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#11
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Newbie
Join Date: Mar 2009
Posts: 13
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@DigitalVampire : Then what should be the best way to do it?
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07-28-2009, 12:41 PM
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#12
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Low Bitrate
Join Date: Dec 2006
Posts: 90
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Quick and easy.
Use a LM7812 based regulator just for the screen. Being linear regulators, 7812 regulators are not very efficient, but will get the job done dirty cheap. Don't forget to heat sink the 7812 chip. Small downside is that when the car is not started, ie when battery voltage is ~12V, 7812 will output only ~10.5V. See if your screen is tolerant to that low voltage. In general, slightly lower voltage should not lead to any problems. When the car is running, the battery voltage goes up to 14.4V and 7812 will regulate the output to solid 12V as required by the screen. Since the voltage differential is not that high, the heat dissipation should not be high either.
IIRC, LM317 is better in terms of drop-out voltage than LM7812 and should help the above idle situation better. LM317 being an adjustable linear regulator, requires 2 resistors to set the output voltage though.
PS: All above assuming that your screen takes less than or equal to 1A current.
Powering 7812/317 from the 19V rail would solve the idle power issue completely, but it would be too inefficient again.
See what suits your situation better.
Last edited by DigitalVampire; 07-28-2009 at 12:47 PM.
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07-28-2009, 01:28 PM
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#13
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Newbie
Join Date: Mar 2009
Posts: 13
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@DigitalVampire : Do you have any schematics to this?
I am not that good when it comes to electronics.
Or should i google it ?
Thanks again
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07-28-2009, 01:44 PM
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#14
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Newbie
Join Date: Mar 2009
Posts: 13
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@DigitalVampire : I think the screen would need 1A. It would be Lilliput EBY701. So according to you, i should power my laptop using DC-DC adaptor and power the screen using LM317 regulator. Right?
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07-28-2009, 02:28 PM
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#15
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Constant Bitrate
Join Date: May 2008
Posts: 173
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Do you already have an M2-ATX or just planning on getting one?
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