Envelope-to: dave@picks.force9.co.uk
Delivery-date: Thu, 26 May 2005 22:16:23 +0100
Message-ID: <01ae01c56238$1d038df0$7900a8c0@athlon1200>
From: "Dave Brown" <tractorb@ihug.co.nz>
To: rsgb_lf_group@blacksheep.org
References: <367832978@web.de>
Date: Fri, 27 May 2005 09:15:59 +1200
Mime-Version: 1.0
Subject: LF: Re: off topics: Inverter 12V/-12V wanted  from DK 8 ND
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

There used to be a low frequency arrangement using a 555 timer as a 
DC-DC converter for charging NICds from a 12 volt supply-was common in 
the amateur literature maybe 20 years ago. Might be the sort of thing 
to use? Just googled and this looks like the sort of thing I mean.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm#5volts.gif

73
 Dave, ZL3FJ

----- Original Message ----- 
From: "Hans-Albrecht Haffa" <dk8nd@web.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, May 27, 2005 2:45 AM
Subject: LF: off topics: Inverter 12V/-12V wanted from DK 8 ND


> Dear Lowfers,
> for a cw-shaping circuit with an op-amp (second order key-klick 
> filter by Jim Moritz) I need an inverter for the negative supply of 
> the op-amp. It is not possible to choose an dc/dc-converter, as most 
> of these devices operate at frequencies of 100 kHz...500 kHz, just 
> where the receiver will run.
> So it is necessary to design an inverter with an transformer running 
> at 100 Hz...500 Hz, what is a good frequency for laminated cores 
> designed for 50 Hz ac. Effectivity may be low, as the circuit will 
> draw only a few mA at voltages of -5...-12V, when powered at +12V. 
> My current thought: Astable multivib followed by driver-transistor 
> and an 230V/12V-12V-Transformer (the 230V ac-windign will not be 
> used).  After rectification  and stabilisation an voltage 
> of -4V...-6V seems to be feasable.
> Have You already done somthing similar?  Any proposals warmly 
> welcome.
>
> 55, Hans-Albrecht
> DK 8 ND           cba
>
>
>
>
> ______________________________________________________________
> Verschicken Sie romantische, coole und witzige Bilder per SMS!
> Jetzt bei WEB.DE FreeMail: http://f.web.de/?mc=021193
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Anti-Virus.
> Version: 7.0.322 / Virus Database: 266.11.17 - Release Date: 
> 25/05/2005
>
> 


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 266.11.17 - Release Date: 25/05/2005