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" <[email protected]>
To: <[email protected]>
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
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