Hello guys i'm new to the forum. I found on a google search and what i'm wanting to do is buy/build a converter for my sleep apnea machine so I can use it in my car when I travel. Its normally plugged into 110vac and transformed to 18vdc at 2.3A , guys i'm a novice at best electronic buff and do have some understanding of it and any help would be great. Thanks in advance.

 

Hello guys i'm new to the forum. I found on a google search and what i'm wanting to do is buy/build a converter for my sleep apnea machine so I can use it in my car when I travel. Its normally plugged into 110vac and transformed to 18vdc at 2.3A , guys i'm a novice at best electronic buff and do have some understanding of it and any help would be great. Thanks in advance.

Most discount stores these days have low power inverters (12V to mains) but unless you pay a fair bit for them, they're likely to be pretty much square-wave output - check your machine can work with that before paying out.

At the current you want 18V at, stepping up from 12V isn't trivial, but there are some chips that can take the edge off it from the likes of LT & Maxim. The real hard work is designing the inductor.

You could always contact the manufacturer and ask whether it would come to any harm if you tried it on 12V.

 

The Texas Instruments Simple Switcher site
http://www.ti.com/ww/en/simple_swit.../index.html?DCMP=simple_switcher&HQS=switcher

shows 6 chips that can do this. 3 of them cost less than a dollar, the efficiency is 95%, and they use up about 1.3 square inches of board space.

Take a peek if you think you can make a circuit board.

 

Just buy a cheap 12V inverter..
http://www.amazon.com/Tripp-Lite-PV...&qid=1376691696&sr=1-2&keywords=tripp+lite+pv

 

Hello guys i'm new to the forum. I found on a google search and what i'm wanting to do is buy/build a converter for my sleep apnea machine so I can use it in my car when I travel.
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So you are planning on sleeping in your car? I hope it's not while you are driving.

 

18v @ 2.3A is 41.4 Watts; with 75% conversion efficiency translates to about 55 Watts of input power, or approximately equivalent to operating one halogen headlamp. If you used a 12v to 120VAC inverter to power your supply, you'd get another 80% to 75% efficiency hit on top of your supply, so around 74 Watts of input power would be required. Attempting to operate your C-PAP machine for any extended period of time will leave your battery too discharged to start your engine again; at the least will be very hard on it. Automotive batteries fall apart quickly if they are deeply discharged.

 

Hello guys i'm new to the forum. I found on a google search and what i'm wanting to do is buy/build a converter for my sleep apnea machine so I can use it in my car when I travel. Its normally plugged into 110vac and transformed to 18vdc at 2.3A , guys i'm a novice at best electronic buff and do have some understanding of it and any help would be great. Thanks in advance.

You may be able to get a Laptop Power Adapter for Car Use that gives 18 V DC.

Ramesh