12v to 6v converter/regulator

D

dreed75

Guest
I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
 
Look at the LM317 regulator with a pass transistor.

The 317 will do up to 1.5 amps (with heatsink).

Just make sure the input voltage is at least a couple of volts higher than
the desired output.


"dreed75" <davidspam@bresnan-dot-net.no-spam.invalid> wrote in message
news:vLqdnWqTy65UaHjfRVn_vQ@giganews.com...
I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
Click to expand...
 
dreed75 wrote:
I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David

The LM2587 is an adjustable, up to 5 amp switching regulator chip.
Click to expand...
http://www.national.com/pf/LM/LM2587.html#datasheet
 
Michael wrote:
Look at the LM317 regulator with a pass transistor.

The 317 will do up to 1.5 amps (with heatsink).

Just make sure the input voltage is at least a couple of volts higher than
the desired output.


"dreed75" <davidspam@bresnan-dot-net.no-spam.invalid> wrote in message
news:vLqdnWqTy65UaHjfRVn_vQ@giganews.com...

I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
Click to expand...
Do you mean 12V like 12.00VDC?
Or do you mean 12V like plug it into a car?
If it's the latter, you have a LOT more things to worry about.
mike

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dreed75 wrote:
I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
Click to expand...
The LM317, LM350 and LM338 and two resistors will all do that.
The chips (on heat sinks) can handle up to 1.5 amps, 3 amps
and 6 amps, respectively.

The LM317 with a PNP pass transistor and a few resistors is
probably your best choice. Simpler, but more costly, would be
the LM250 or LM338. Here's the circuit with the pass xsistor:
PNP
2N2955
e c
+12 -----+------ ---------------------+
| \ / |
3[R1] ----- |
| | ------------ |
+--------+------|in LM317 out|---+--- Vout +6
| ref | |
------------ [R2]240
| |
+----------+
|
[R3] 910
|
Gnd

There will be a voltage drop across R1 (3 ohms) as the LM317
provides current to the load. The more current that is
drawn, the greater the voltage. The effect is to cause the
transistor to conduct when the current drawn is about 200 mA,
and the more current that is drawn, the harder the transistor
conducts. R2 (240 ohms) and R3 (910 ohms) form a voltage
divider that "programs" the LM317 to produce very close to
6 volts. If you need it to be precisely 6.00 volts, substitute
a 10 turn, 1000 ohm pot for R3 and adjust it to the exact voltage.

Consult the datasheet for the LM117/LM317 for more detail.
http://www.national.com/ds/LM/LM340.pdf

Ed
 
On Tue, 26 Jul 2005 03:35:21 -0500,
davidspam@bresnan-dot-net.no-spam.invalid (dreed75) wrote:

I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
Click to expand...
Unless you want and know how to dissipate appropriately 18 W, you must
go for a switching converter. Forget about linear regulators.
 
Hi,

You may not want to do this but by using two IR2110'S and 4 fets and a
toroid with two wires bifilar wound . Connected as you would a push pull,
center tapped 6 to 12 volt converter and replace the two diodes with two
fets. This must be driven with a 40 to 50 % on each half cycle. You now have
a synchronous rectified voltage doubler that is bi-directional and if a 12v
charger is applied to the 12 volt output you will also charge the 6 volt
battery.

I have built such a device for a friend to add a 12v battery to a triumph
motorcycle because the 6v batteries are no longer made. The 6v charger
charges the 12v battery and the electrical system is all 6v. Above I used
the 555 timer and 4013 to divide by two and give a symmetrical output.

Ray







"Mochuelo" <cucafera@RE_MO_VE_THIStelefonica.net> wrote in message
news:p6see11p4qqt50bvok7m6va1k506uhl2tr@4ax.com...
On Tue, 26 Jul 2005 03:35:21 -0500,
davidspam@bresnan-dot-net.no-spam.invalid (dreed75) wrote:

I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David

Unless you want and know how to dissipate appropriately 18 W, you must
go for a switching converter. Forget about linear regulators.
Click to expand...
 
You could do a little experimenting with a mobile phone car charger -
just change the output voltage divider resisters and bobs your auntie

David - who finds the local tips are full (big exaggeration, but..) of
them

dreed75 wrote:

I have looked all over for a chip or a schematic that allows me to
convert 12v to 6v and I can't find anything. I can find 12v to 5v
with no problem at all but I need 6v. Would a simple voltage divider
work? The load changes so I don't think a voltage divider will work
but I am not sure. The current will be up to 3A at some times but as
low as 500mA at other times. Thanks.

David
Click to expand...
 
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