[Milsurplus] 12 to 24 volt conversion, the issue of cost

[Tom Dawson]

Mike,


I don't think anyone's recommending that you mortgage the farm for a new 
truck, it is just an interesting topic and there are a lot of possibilities. 
And threads tend to drift particularly if contributors pick up in the 
middle.

On your DC-DC converter project, I might recommend that you investigate 
boost converters as the inductors are a single winding.  I've made 
experimental converters with just a 555 driving the switch transistor. 
Regulation is achieved via adjusting the duty cycle (something other than a 
555 is needed if you want to regulate this way, but the 555 is a good place 
to start).  National semiconductor has application which greatly notes on 
their controller chips and boost  supplies in general.

Also there is Linear Technology with a substantial line of switching 
regulator chips of various configurations.  They also provide a free spice 
simulator with a "schematic drawing" input which greatly simplifies using 
spice.  the program is SwitcherCAD IV.  Quite handy.

The boost switcher appeals because of the simplicity of the inductor design 
and several amps can be achieved with inductances on the order of 50 uH if 
the frequency is high enough.  In practice you'll need to add input and 
output filtering to suppress the EMI.

As an example of an application the Elgar GIPS series of  MIL UPS employs a 
24 to 80 volt boost switcher at 400 Watts (5 A at 80 Volts) with an inductor 
about 3 inches in diameter.  The 80 volts is then turned into 120 Volts 60 
Hz sine wave but that feature is not germane to your project.

Anyway, some food for thought.

73

Tom
WB3AKD

----- Original Message ----- 
From: "Michael Tauson" <wh7hg.hi at gmail.com>
To: <boatanchors at lists.tempe.gov>; <boatanchors at mailman.qth.net>; 
<milsurplus at mailman.qth.net>
Sent: Thursday, October 08, 2009 2:36 PM
Subject: [Milsurplus] 12 to 24 volt conversion, the issue of cost


> As the one who started this thread, I really like all the responses so
> far and they've proven to me that many solutions do exist.  But darned
> near every one has been something that has a price tag that I hope
> someone else is willing to pick up because I sure as heck can't.  Let
> me get this perfectly clear to everyone, I LIVE ON A VA PENSION AND
> BARELY HAVE ENOUGH TO MANAGE WHAT I CAN DO NOW!  (Oh, and I'm not fond
> of rice & beans as a constant diet.)  Please, folks, don't spend money
> I simply don't have or try to rebudget that which I do but rather
> think cheap.  Some of the "cheap & easy" solutions people have
> directed me to are my food budget for no less than one month and
> upwards of three - and that is at commissary & Wally World prices.
>
> Only a few actually caught on to what I want to do - build (yes,
> build.  You know, individual components and winding transformers and
> soldering and all like that there stuff.) an inexpensive 12-to 24 volt
> converter and learn about toroids at the same time.  How that got to
> buying trucks is way beyond my comprehension but it tells me the
> thread has gotten out of hand.  Go back to my original post to see
> what I'm looking for ... and, as a hint, it has nothing to do with
> adding batteries, adding alternators, or buying vehicles.
>
> Let's see how quickly I get flamed for this.  I think I even know
> who'll be the ones to cast the first grenades.
>
> BEst regards,
>
> Michael, WH7HG
> -- 
> http://www.nationalmssociety.org/chapters/NTH/index.aspx
> http://wh7hg.blogspot.com/
> http://kludges-other-blog.blogspot.com
> Hiki Nô!
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