DC/DC converter

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EyeMWing

Banned
Jun 13, 2003
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I'll show you what happens.

I know, this isn't a correct diagram. Sue me.

The DPDT switch lacks connections for the third pair (clearly Visio sucks), is a ON-OFF-ON 3-position unit, and the DC/DC converter is one big gray area. Also, a laptop is one helluva resistor :p

Anyway, ignoring the problems with that diagram, I have one major problem remaining. The DC/DC converter. First, can someone recommend to me exactly what specs I should be looking for? Can I build one to do this myself? (Which I'd sort of prefer, since all the high-end DC/DC converters on Mouser seem to be HELLACIOUSLY expensive, and I could just as easily buy the $110 car adapter and use that from a single 12v battery, and just switch batteries mid-day for a whole $10 more)

Other thoughts/comments?
 
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bobsmith1492

Diamond Member
Feb 21, 2004
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If your laptop is a DTR, it probably draws a ton of power; mine draws less than 65W, and it's just a P-M. Anyway, yours could probably draw 100W. A 100W DC-DC converter will be immensly expensive assuming you can even find one of the right voltage. An inverter would probably be a better bet; get a cheapy couple hundred watt 12V to 120VAC inverter and just use your regular power supply.
 
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EyeMWing

Banned
Jun 13, 2003
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Originally posted by: bobsmith1492
If your laptop is a DTR, it probably draws a ton of power; mine draws less than 65W, and it's just a P-M. Anyway, yours could probably draw 100W. A 100W DC-DC converter will be immensly expensive assuming you can even find one of the right voltage. An inverter would probably be a better bet; get a cheapy couple hundred watt 12V to 120VAC inverter and just use your regular power supply.
Click to expand...

It'll run on as a little as 35w (at a whopping 800MHz), but will take a full 135 when it's charging the internal battery and running at full power.

I'd considered an inverter, and the more I shop around, the more it looks like it's the only way to go. Problem with that being that I have to buy a second AC adapter ($80) if I'm going to run the same switched setup (Or I could move to a relatively exotic 3PDT ON-OFF-ON switch and switch the AC portion of the line)
 
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bobsmith1492

Diamond Member
Feb 21, 2004
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Why would you need a second adapter? Just unplug it and plug it into the inverter; simple switch.
 
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JTWill

Senior member
Feb 2, 2005
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Why not simply use a LM 317 regulator. Its adjustable and good for 1.5 amps. Light and small circiut for your unit.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm#317.gif


The LM317T is a adjustable 3 terminal positive voltage regulator capable of supplying in excess of 1.5 amps over an output range of 1.25 to 37 volts. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof.

You can build one for less than $20 in parts from radio shack 2n3055 transistors can be used to bring the current output up to 10amps. google the part # .The great thing about the circuit is its current protection in shuting itself down on overloads.
 
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EyeMWing

Banned
Jun 13, 2003
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Originally posted by: bobsmith1492
Why would you need a second adapter? Just unplug it and plug it into the inverter; simple switch.
Click to expand...

Switching plugs manually is ungeeklike.
 
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bobsmith1492

Diamond Member
Feb 21, 2004
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Hey JTWill, do you have any schematics that show how to use 2n3055s in conjunction with a regulator? I've got tons of those, but never have found out how to use them.

Gotcha EyeMWing. You could switch the AC if you really have to; there are only 2 wires, so a DPDT would still do it (unless you run your computer on 3-phase power??? Maybe it's more of a hog than I though :p)
 
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