How to: automotive 12vdc regulator ?

[SAH]

I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about 2
or 3 amps max. I need to run some small devices that require a 12Vdc input.

Any and all help appreciated.

Sean.

 

[Thomas C. Sefranek]

"the best and cheapest way"

Often contradictory!

I'll bet your "device" will work just fine on the "varying ... output".
(If not, it's a crap device!)

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...

I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.

--
*
| __O Thomas C. Sefranek WA1RHP@ARRL.net
|_-\<,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

 

[SAH]

Agreed, I am hoping that it will be the case but the question was posed for
the worst case scenario. The device in question is a cold cathode neon tube
used in PC Mod applications. You can pick them up for 10 bucks in a 12"
tube. They come with a 4 pin Molex connector to provide 12Vdc to an
inverter. Now, in a PC application, the inverter will see a pretty stable
12Vdc, but in a car it will obviously vary up to 3 volts on the high side,
worst case scenario. What would be the cheapest was to have a 12 Vdc limiter
?......or maybe somebody here has already tried this and has some experience
with them.....?

S.

"Thomas C. Sefranek" <WA1RHP@ARRL.NET> wrote in message
news:O_6dnc5naOPGmmuiRVn-jA@comcast.com...

"the best and cheapest way"

Often contradictory!

I'll bet your "device" will work just fine on the "varying ... output".
(If not, it's a crap device!)

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.


--
*
| __O Thomas C. Sefranek WA1RHP@ARRL.net
|_-\<,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

 

[Jack Snodgrass]

On Fri, 02 Jan 2004 17:42:01 -0400, SAH wrote:

I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about 2
or 3 amps max. I need to run some small devices that require a 12Vdc input.

Any and all help appreciated.

Sean.

I recently ordered ( but haven't received )
http://store.ituner.com/ituner/itps.html
for a different 12volt application. Not sure
what your version of cheap is.

jack

 

[SAH]

Well, I may have to got that route. If I don't get any first hand info soon
I'll just throw one in a car and see what happens. I'm hoping that they are
not all that sensitive.
"Jack Snodgrass" <jacks_temp_id_200401@verizon.net> wrote in message
newsan.2004.01.03.00.36.40.831581@verizon.net...

On Fri, 02 Jan 2004 17:42:01 -0400, SAH wrote:

I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about 2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.

I recently ordered ( but haven't received )
http://store.ituner.com/ituner/itps.html
for a different 12volt application. Not sure
what your version of cheap is.

jack

 

[Chan]

You can't regulate to 12V if your input is 12-14.5. This is because your
regulated will need to drop at least 0.6V (assuming it's just one power
transistor). So you can have a max of 11.4V.

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...

I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.

 

[Byron A Jeff]

In article <bt6ilv$cbe$1@hercules.btinternet.com>,
Chan <dsadsdddads@btinternet.com> wrote:
-
-You can't regulate to 12V if your input is 12-14.5. This is because your
-regulated will need to drop at least 0.6V (assuming it's just one power
-transistor). So you can have a max of 11.4V.

PNP bipolars and P-channel MOSFETs often will only drop 0.2V over low to medium
currents. Check out the Vsat parameters.

BTW with an auto regulator, that's very rarely the issue. There are three
issues that need to be dealt with:

1) Starter voltage drop out. When the car is starting, often the battery will
drop as low as 8V. You can't keep regulation at that voltage and it'll
often reset the equipment connected. I resolved this issue in my car
computer by having a Lead Acid battery before the regulator and a connection
between the car electrical system and the battery via a diode. So the
car system would charge the battery, and when the car started the diode
prevented the electrical system from drawing power from the extra
battery.

2) Surges. Auto electrical systems can have spikes way above 14V. So you should
have surge/spike protection. A MOV or a zener based power shunt should
be at the head of the electrical system. Also a power resistor can limit
the amount of current into the regulator.

3) Noise. You'll need to sprinkle caps into your regulator to smooth out
the noise typically found in the electrical system.

BAJ

 

[Keith R. Williams]

In article <bt6ilv$cbe$1@hercules.btinternet.com>,
dsadsdddads@btinternet.com says...

You can't regulate to 12V if your input is 12-14.5. This is because your
regulated will need to drop at least 0.6V (assuming it's just one power
transistor). So you can have a max of 11.4V.

One could with a switching regulator.

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

--
Keith

 

[Robert C Monsen]

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...

I need to know the best and cheapest way to regulate my cars varying 12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.

Look at the LT1371. Its a switching regulator, requiring a couple of
external inductors, diodes, etc. It'll let you draw 3A.

Regards,
Bob Monsen

 

[Greg Neill]

"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:CBHJb.725039$HS4.5405533@attbi_s01...

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.



Look at the LT1371. Its a switching regulator, requiring a couple of
external inductors, diodes, etc. It'll let you draw 3A.

Doesn't anyone use zener diodes anymore?

 

[Robert C Monsen]

"Greg Neill" <gneillREM@OVE.netcom.ca> wrote in message
news:QO_Kb.18190$OX.633434@wagner.videotron.net...

"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:CBHJb.725039$HS4.5405533@attbi_s01...

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.



Look at the LT1371. Its a switching regulator, requiring a couple of
external inductors, diodes, etc. It'll let you draw 3A.

Doesn't anyone use zener diodes anymore?

I wonder how long a 12V zener would last as a shunt at 14V? He wants 3A.

Regards,
Bob Monsen

 

[SAH]

Thats an idea. 3 amps would be the max for sure, probably only half that
most likely. Could you give me a particular zener number, maybe I can track
one down ?


"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:AL6Lb.311723$_M.1811488@attbi_s54...

"Greg Neill" <gneillREM@OVE.netcom.ca> wrote in message
news:QO_Kb.18190$OX.633434@wagner.videotron.net...
"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:CBHJb.725039$HS4.5405533@attbi_s01...

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.



Look at the LT1371. Its a switching regulator, requiring a couple of
external inductors, diodes, etc. It'll let you draw 3A.

Doesn't anyone use zener diodes anymore?



I wonder how long a 12V zener would last as a shunt at 14V? He wants 3A.

Regards,
Bob Monsen

 

[Bill Bowden]

"Robert C Monsen" <rcsurname@comcast.net> wrote in message news:<AL6Lb.311723$_M.1811488@attbi_s54>...

"Greg Neill" <gneillREM@OVE.netcom.ca> wrote in message
news:QO_Kb.18190$OX.633434@wagner.videotron.net...
"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:CBHJb.725039$HS4.5405533@attbi_s01...

"SAH" <webit@[NOSPAM]accesswave.ca> wrote in message
news:GAlJb.195438$PD3.5906023@nnrp1.uunet.ca...
I need to know the best and cheapest way to regulate my cars varying
12 -
14.5 Vdc output to a reasonably steady 12 Vdc. I would only require
about
2
or 3 amps max. I need to run some small devices that require a 12Vdc
input.

Any and all help appreciated.

Sean.



Look at the LT1371. Its a switching regulator, requiring a couple of
external inductors, diodes, etc. It'll let you draw 3A.

Doesn't anyone use zener diodes anymore?



I wonder how long a 12V zener would last as a shunt at 14V? He wants 3A.

Regards,
Bob Monsen

You can make a big zener diode with a NPN power transistor
and small zener. Hook the zener from base to collector
so that the transistor only conducts at the zener voltage
plus 0.7 for the b/e voltage. Put the big zener in parallel
with the load as a shunt regulator and add a 0.2 resistor
in series with the battery. If the battery is at 12 volts you
lose 0.6 volts at 3 amps. If the battery is at 14 volts,
the transistor drops 12 volts at 10 amps (120 watts) and the
resistor dissipates 20 watts.

-Bill