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

[Tom Dawson]

Jim,

Only drawback to the 555 is the duty cycle limitation in astable mode which 
won;t exceed 50 %.  Given probably losses in the switch transistor and 
inductor, a 12 to 24 boost converter would need more that 50% DC.

Still it is a great place to start and I've used it with a Ford ignition 
coil and TV voltage tripler to power surplus image converter tubes.

73

Tom
WB3AKD


----- Original Message ----- 
From: "Jim Whartenby" <antqradio at sbcglobal.net>
To: <milsurplus at mailman.qth.net>
Sent: Friday, October 09, 2009 1:31 AM
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.
>

______________________________________________________________
Milsurplus mailing list
Home: http://mailman.qth.net/mailman/listinfo/milsurplus
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Milsurplus at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html