12vac to 12vdc

[s cass]

12vac to 12vdc?
how to ?

12vac from 12vac landscape lighting transformer 100 to 200 watts
to
12 - 24vdc .350ma

thanks

 

[Fred Bloggs]

12vac to 12vdc?
how to ?

12vac from 12vac landscape lighting transformer 100 to 200 watts
to
12 - 24vdc .350ma

thanks

Use a voltage doubling rectifier and filter capacitor hookup to drive a
National LM2675-ADJ simple switching regulator. See the "Power" section
at http://www.national.com for more detail and to run a simulation.

 

[TCS]

Use a voltage doubling rectifier and filter capacitor hookup to drive a
National LM2675-ADJ simple switching regulator. See the "Power" section
at http://www.national.com for more detail and to run a simulation.

Do you mean a fullwave rectifier? Voltage doubling is an entirely
different beast.

No need for a switching regulator either. A 7812 will do the trick
just fine. 12Vac=~17Vpeak; the 5V extra is plenty to cover the 7812's
voltage drop.

Summary: 12vac -> full wave rectifier -> cap (500uf or so) -> 7812 =
12VDC

 

[N. Thornton]

s cass wrote:

The 12 volt AC waveform swings from almost positive 17 to almost
negative 17 volts. You can pass this through a diode bridge and
produce full wave DC that can charge a capacitor. This will give you
about 15 to 16 volts DC which can be regulated to 12 volts by a 7812
regulator (mounted on a heat sink).

Hi.

Just one additional point: transformer regulation. IRL you can expect
10% more voltage out because your 100w transformer is only lightly
loaded.

You wont need any regulator if youre happy with 16-19v rather than
12v.


Regards, NT

 

[Fred Bloggs]

Do you mean a fullwave rectifier? Voltage doubling is an entirely
different beast.

No need for a switching regulator either. A 7812 will do the trick
just fine. 12Vac=~17Vpeak; the 5V extra is plenty to cover the 7812's
voltage drop.

Summary: 12vac -> full wave rectifier -> cap (500uf or so) -> 7812 =
12VDC

I was taking the "12 - 24vdc .350ma" in the body of the post to mean he
wanted an adjustable output over that range. Now it is becoming clear
that the OP has copied labels he sees on some some junk he owns- since
nothing adds up.