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

[dsmaples at comcast.net]

All: Consider this.  Set up a 24 VDC center-tapped transformer with two sets of switching transistors and some way to excite them, as you would with a standard inverter.  Then just hang a diode off of each end of the transformer and tie the diode cathodes together at a filter cap.   



As far as I can tell, you'll wind up with about 24 VDC at the filter cap.  Size the diodes correctly, and you should be done. 



This should be something you can build up using either (a) an old linear power supply, or (b) an old DC-AC inverter, or (c) an old DC-DC power supply for vacuum-tube hardware. 



Whadda ya think? 



Dave WB4FUR 



  
----- Original Message ----- 
From: "Jim Whartenby" <antqradio at sbcglobal.net> 
To: milsurplus at mailman.qth.net 
Sent: Thursday, October 8, 2009 9:31:01 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [Milsurplus] 12 to 24 volt conversion, the issue of cost 

You PWM a NE555 using pin 5 which connects to the top junction of the three 5k ohm resistors used to set the limits of the voltage comparators. 

The 555 should make a usable PWM for the step up converter. 
Jim 

--- On Thu, 10/8/09, Tom Dawson <wb3akd at earthlink.net> wrote: 

> 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. 
> 

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