12 volts into 24 volts

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12 volts into 24 volts

Post by JKMADSCI » Wed Aug 25, 2004 1:24 pm

Does any one have a schematic for a circuit that wouuld convert 12 volts dc into 24 volts dc.
I need 24 volts dc at 1.5 amps. The source voltage would be a car battery. I realise that this will require some type of switching ac circuit.
Thanx in advance

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Dave Dixon
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Re: 12 volts into 24 volts

Post by Dave Dixon » Wed Aug 25, 2004 1:46 pm

Try here...
National Semi power semi.
Just poke in the values in the center column for
Vin min. / Vin max. / Vout and Current.
It'll lead you to a simple switcher circuit.
We use them in our aircraft instruments quite
Good luck, hope this helps.

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Re: 12 volts into 24 volts

Post by jollyrgr » Wed Aug 25, 2004 2:45 pm

The simplest way to do this is with "off the shelf" parts. I suggest getting a simple 12VDC to 120VAC inverter. There are all sorts of these available and, with your low current requirements, you could get away with one used for laptops. Walmart, Target, and Kmart sell these things in the automotive section. I have seen these in their stores and here is an example from Target's web site:<p>http://www.target.com/gp/detail.html/sr=2_2/qid=1093 471494/ref=sr_2_2/601-5335012-9204924?%5Fencoding=UTF8&asin=B00006RK5I<p>This little 75 watt job will do nicely. There are bigger models with lots more power but you don't need to go that high. The web site shows a device for $30 but I have seen them much cheaper. If these are not in the automotive accessories, try the electronics department. Radio Shack sells these as well but for double the price shown above.<p>From there convert the 120VAC to 24VDC. You can do a "roll your own" DC power supply or look to the surplus market for a nice switching supply. One that comes to mind is from All Electronics. See this item:
http://www.allelectronics.com/cgi-bin/c ... type=store<p>This supply will take in 100 to 240 VAC and convert it to a regulated 24VDC at 3Amps. Thus the input voltage does not need to be that regulated. This supply is open frame; i.e. it does not include a case. (I'll have a suggestion later.)<p>All Electroncis also has a 100 watt inverter for $25. See this:<p>http://www.allelectronics.com/cgi-bin/c ... type=store<p>I suggest that you get a standard 120VAC to 24VDC (wheter you build your own or buy a pre-made module) and allow it to run off AC. Put it in its own case with a standard line cord input. Use a standard inverter to convert the DC to AC. You can go with the small styles I presented or if size is not a concern you can use a bigger device in the 300 watt or larger range. Doing this will allow you to have flexibility to use the 24VDC supply from an AC outlet and allow you to use the inverter for other items. If you still want a dedicated supply you can extract the AC inverter from its case and put the guts inside another case with a 24VDC supply of your choice. <p>With the items shown from All Electronics you can have the circuit running for less that $40 (not including case) and it will take about half an hour to assemble. The parts alone for rolling your own from scratch will cost a lot more unless you have a very well stocked junkbox. Plus you know it will work the first time. If not, troubleshooting the "off the shelf" solution I have presented will be quite easy.<p>If battery life is a concern then you WILL have some wasted power. Another thing you could try and find would be a DC to DC converter with Isolation. These devices are quite neat. They take in a range of voltages (let's say from 11 to 15 Volts DC and put out a clean 12VDC that is isolated from the source. I tried to find one to go directly to 24 volts DC but was unable to locate one. It might be possible to take two of the 12 volt modules and hook the outputs in series. I have never done this and it is only a theory. Has anyone done this before? Please let me know.
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Chris Smith
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Re: 12 volts into 24 volts

Post by Chris Smith » Wed Aug 25, 2004 9:43 pm

"Pico" makes neat little units already.

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