24v supply

Archiver

In the past, I've been able to run my stamp from a 12vdc supply directly to
the regulator on the stamp. My current project will be powered by a 24vdc
source. Is it as simple as running the power thru a 7812 regulator to get
it down to 12v or is there more to it.

Mark

Archiver

You'll have a 12V standoff, which will give you something like 18W of heat,
which IMHO is a bit much and will call for a good size heat sink. I would
either divide the 24V down to something like 15V ( I think the minimum
standoff V is 3.0, but you had better check the LM7812 data sheet on this)
This way you would only need to dissipate 4.5 W or so. Of course, you'll
just make heat in your divider, so while you're regulator heat would be more
manageable, it would not be very efficient either. You might consider either
using an adjustable regulator like the LM317, or perhaps a DC-DC converter
to get the output voltage down and end up with a more efficient system
overall.

Chris

>

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Original Message

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> From: Mark Schmidt [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=9iB2R63DrZI4A0ima08CisGO7tk_k5cvgFB3GLRahEFGENtoxEdjcuki8dE2qFt83IebONpZJcYLBCk]mschmidt@g...[/url
> Sent: Monday, September 17, 2001 9:51 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] 24v supply
>
>
> In the past, I've been able to run my stamp from a 12vdc
> supply directly to
> the regulator on the stamp. My current project will be
> powered by a 24vdc
> source. Is it as simple as running the power thru a 7812
> regulator to get
> it down to 12v or is there more to it.
>
> Mark
>
>
>
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Archiver

I think a 7812 in a TO220 package should work for you.

The maximum input for the 7812 is 35 VDC and thus with 24 VDC, you
are okay.

When running with no heatsink, the max power dissipation is about
3W. Thus, with the 12V (24 - 12) drop across the regulator, your
current is limited to about 250 mA. With a modest heatsink, you can
roughly double this.

But, if you are not driving a motor or similar hungry device, you
probably don't draw anything close to this 250 mA.

Hope this help.

Peter H. Anderson, http://www.phanderson.com/stamp/


--- In basicstamps@y..., "Mark Schmidt" <mschmidt@g...> wrote:
> In the past, I've been able to run my stamp from a 12vdc supply
directly to
> the regulator on the stamp. My current project will be powered by
a 24vdc
> source. Is it as simple as running the power thru a 7812 regulator
to get
> it down to 12v or is there more to it.
>
> Mark