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.

Thank you everyone for suggestions !!!

73 de Riccardo IK5WQO

In article , "Rightrik" wrote:

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.

Riccardo-

If you have a 12 volt inverter of any kind, you might look at the primary
side of its circuit. If the transformer center tap is connected to 12
volts and it uses switching transistors to alternately connect the ends of
a transformer winding to ground, then you can connect rectifiers from the
ends of the transformer winding, to a filter capacitor for a plus 24 volt
supply.

When one end is grounded, the center is still plus 12 volts, so the
opposite end of the winding becomes plus 24.

73, Fred, K4DII

Riccardo-

If you have a 12 volt inverter of any kind, you might look at the primary
side of its circuit. If the transformer center tap is connected to 12
volts and it uses switching transistors to alternately connect the ends of
a transformer winding to ground, then you can connect rectifiers from the
ends of the transformer winding, to a filter capacitor for a plus 24 volt
supply.

When one end is grounded, the center is still plus 12 volts, so the
opposite end of the winding becomes plus 24.

Thanks Fred, but i would like the dc-dc inverter solution to be able to
operate the switch from any 12/13,8 vdc source.

73 de Riccardo IK5WQO

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.

If "operate" does NOT mean "hold" (i.e., if you just need pulses of 24 volts)
then you can wire a capacitor to a switch such that the capacitor charges
to 12 volts and then ADDS to that same 12 volts to operate the relay.
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

If "operate" does NOT mean "hold" (i.e., if you just need pulses of 24
volts)
then you can wire a capacitor to a switch such that the capacitor charges
to 12 volts and then ADDS to that same 12 volts to operate the relay.

Well, i need a stable 24 v dc voltage, not just a voltage peak to 24 and
back to 12.

Thank you,
73 de Riccardo IK5WQO

"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