KEMO Electronics (germany) make these items. They have an interesting
range of
small modules with various functions. Have a look at their web page:

http://www.kemo-electronic.com/en/module/m029/index.htm

They are wholesale only, but have distributors around the planet.

This should be the best solution, but (up to now) they don't answer to my
email...

73 de Riccardo IK5WQO

I think you might find a "wall-wart" power supply for a computer printer
to do the job.

You can find these in voltages like 24-28v @ 1 amp for maybe $10 new in
the US. Of course ours are 120v but I imagine you have the 240v types
available over there in I-land.

-Bill

Thank you Bill, but i want to start from 12/13,8 vdc to reach the famous 24
vdc, and do not want to use a 120 or 220 vac supply...

73 de Riccardo IK5WQO

This may be slight overkill (they claim it's good for 100W) but it's
inexpensive:

www.oatleyelectronics.com/kits/k168.html

Alternatively, you could put together something quite simple using
an MC34063A (try Google) - easy to use, readily available.

Bill

Thank you Bill.

73 de Riccardo IK5WQO

Netgeek wrote:
This may be slight overkill (they claim it's good for 100W) but it's
inexpensive:

www.oatleyelectronics.com/kits/k168.html

Alternatively, you could put together something quite simple using
an MC34063A (try Google) - easy to use, readily available.

That unit could run cooler or produce more output if the rectified
secondary were stacked on the +12 input, so it had to produce only the
additional voltage. Just cut the secondary turns almost in half.

John Popelish wrote:
Netgeek wrote:

This may be slight overkill (they claim it's good for 100W) but it's
inexpensive:

www.oatleyelectronics.com/kits/k168.html

Alternatively, you could put together something quite simple using
an MC34063A (try Google) - easy to use, readily available.


That unit could run cooler or produce more output if the rectified
secondary were stacked on the +12 input, so it had to produce only the
additional voltage. Just cut the secondary turns almost in half.

Or better yet, just add a few turns past the point where the drains
connect (which go up to almost twice the input supply voltage), and
connect those points to the output through one diode, each. Eliminate
the secondary, all together and raise the efficiency a bit more. But
there should be a filter choke between the rectifiers and the output
filter capacitor to average the slightly over voltage pulses with the
zero volt spaces between them.

On Sun, 8 May 2005 01:53:26 +0200, "Rightrik" wrote:

KEMO Electronics (germany) make these items. They have an interesting
range of
small modules with various functions. Have a look at their web page:

http://www.kemo-electronic.com/en/module/m029/index.htm

They are wholesale only, but have distributors around the planet.

This should be the best solution, but (up to now) they don't answer to my
email...

Because they are strictly wholesale only, they may not reply. In the past I
have had a reply which directed me to the distributor here in Australia.

"Rightrik" wrote in message
...
Hello, i need a little, low power (about 500 mA) step up converter from 12
v
dc to 24 v dc to operate correctly a 4 ways coaxial switch.
I have found project on the net, but i wonder if there is a ready, little,
not ott expensive kit or ready-to-go-module to obtain this 24-26 v dc
voltage from 12 (13,8) dc volt input.

Thank you,
73 de Riccardo IK5WQO


These relays will usually hold in fine on 12 VDC they may even work OK. If
they will not work there is a circuit that charges a capacitor to 12vdc and
when the relay is energized the cap is momentarily in series with the 12
volt supply. This will pull the relay in then the 12 volts should be enough
to hold it. Google on "operating 24 volt relays on 12 volts" Circuit is very
simple if you can find it.One advantge of using this circuit is that the
relay coils are not stressed as much. A coil that runs hot at 24 may be
cool to the touch on 12.

On Tue, 10 May 2005 20:41:10 GMT, "Jimmie"
wrote:

These relays will usually hold in fine on 12 VDC they may even work OK. If
they will not work there is a circuit that charges a capacitor to 12vdc and
when the relay is energized the cap is momentarily in series with the 12
volt supply. This will pull the relay in then the 12 volts should be enough
to hold it. Google on "operating 24 volt relays on 12 volts" Circuit is very
simple if you can find it.One advantge of using this circuit is that the
relay coils are not stressed as much. A coil that runs hot at 24 may be
cool to the touch on 12.

You might want to check this.

I have dealt with circuits which "should have" worked, but enough
components pulled down the voltage to where relays would not stay
energized, and would rapidly cycle as they struggled to stay
energized.

Happy trails,
Gary (net.yogi.bear)
--
At the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

Because they are strictly wholesale only, they may not reply. In the past
I
have had a reply which directed me to the distributor here in Australia.

They just replay me : "we don't have any distributor for Italy, sorry"...

:-(

Yes, i've seen this "pump-up" circuit but i would prefer a real 24 vdc to
make sure the rele is correctly energized.
My 26 vdc - 4 ways Dow-Key coax rele works also with 12 vdc, but the problem
is : "is it affordable at this coil voltage???"
A stronger 24 vdc would be better...

Thank you,
73 de Riccardo IK5WQO