Thread: Another Noob with a power suply question.

maybe, but a dc-dc would be more reliable. compared to risking messign up your eeepc, or screen, the cost for a reliable dc-dc is justifiable

My current system (a Fujitsu Stylistic 3400 tablet PC) is powered in a fundamentally similar way. I simply bought an inexpensive car charger for the tablet, cut off the cig lighter end, and have it installed behind the dash and wired into a source of switched +12 in the car (I believe I'm tapped into the radio circuit.)

With a traditional computer (like an EeeBox) such a solution wouldn't be practical as the unit does not contain a step-up (boost mode) switching supply, and therefore it shuts off when the system voltage is below a certain threshold. Mine seems to be happy at 12.5 volts and higher. So it does not work when the starter is turning, nor when battery voltage is low, as when the car is very cold.

With a laptop, however, this is not a problem. The PC simply senses when the external supply is not present and switches to internal battery power. Then, once the car's voltage is high enough to turn the power supply back on, the laptop switches to external power and recharges itself.

I've been running like this for close to four years now, and have no issues.

A DC-DC power supply will regulate the power and make a cleaner signal. These will also allow you to do a delay on which can prevent a power surge between the ignition on-crank-ignition on cycle.

So I found a little more out about the requirements of my system, the computer needs 9.5V at 2.3A kinda of odd voltage requirement. Can I get away with running something close to that say 10V at 2.5A, and what power supplies are out there for this voltage range? I'd also like to have the feature that automatically sleeps and wakes the computer when you turn off and start up the car.

for that, i would use a dc-dc power supply to clean up the input voltage, and then build a resistor pack that could take 5 amps continous that would output 9.5 volts-- and i really would try to get it as close as possible to the 9.5 volts(9.4-9.6 regulated)-- a half volt to computers is huge.

but that is what i would do-- becsaue it is only 9.5 volts, a cigarette lighter adapter should work, as long as it can provide the 2.3 amps of current

Originally Posted by soundman98

for that, i would use a dc-dc power supply to clean up the input voltage, and then build a resistor pack that could take 5 amps continous that would output 9.5 volts-- and i really would try to get it as close as possible to the 9.5 volts(9.4-9.6 regulated)-- a half volt to computers is huge.

but that is what i would do-- becsaue it is only 9.5 volts, a cigarette lighter adapter should work, as long as it can provide the 2.3 amps of current

I would have no idea how to build a resistor pack, my experience with electronics doesn't go much further than hooking up the home entertainment system. If its a matter of wire A in plug B I can figure it out now matter how complex it gets, but when it comes to circuits and building things I'll admit I'm totally lost.

If I were to just hard wire a cigarette lighter adapter would there still be a way to have the feature that auto sleeps and wakes the computer when power is cut and turned on?

anyone?

So I've got my computer wired to the glove box by splicing a cigarette lighter car charger into my cars 12+v power. I didn't go with a DC-DC power supply because my Asus EEE netbook is an odd voltage (9.5V at 2.3A). But today I saw this one the mp3Car front page, http://store.mp3car.com/Intelligent_..._p/pwr-034.htm if I'm reading this products description correct it's full adjustable in .25V increments anywhere between 5-24V. Meaning this would be able to supple my odd 9.5V requirements, right?. I can't tell what the output is in amps, I need 2.3A. It also looks like it can auto-sleep/auto-wake my laptop for me.
Can someone tell me if this will work for me?

Another question, because of the small harddrive space on my netbook, I've been running a portable USB harddrive with it. It's Velcro-ed to the back of the laptop.
When I have the computer plugged into the car, and the accessory on, but the engine not running, when the laptop is accessing the external drive it is constantly switching between AC and battery to get enough power for the usb drive. It doesn't do this if the engine is running, only when the electric is on but the engine is off.
Would this device also solve this?

Thanks for your help, sorry if these are stupid questions, I'm still trying to learn this stuff.

someone?