Power supply question
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Posts: 46,084
I have a requirement for the following power supply:
12volt input
5volt output
500ma output current
I have been using the 7805 regulator for this but the heat output due
to the rather high differential voltage (7v) is not acceptable. I need
a more efficient solution which is easy to build and inexpensive. As a
calibration point my 7805 solution uses one regulator and two capacitors
on a 1.5" square PCB.
Is there a good solution to my requirements. I am using the 7805 solution
to power a Garmin 25 board. The board and power supply are mounted inside
an aluminum chassis box approximately 4" x 3" x 3". Because of the use,
both the G25 and the power supply must be enclosed. The 12volts comes
from the battery in my car. I am very concerned about the heat buildup
inside the box. I have bored some holes in the top of the box which helps
some. However, I believe that the real solution is to have a more efficient
power supply
Any suggestions or ideas would be gratefully appreciated. I would also
appreciate a copy (CC) of any response be sent to my Email addess.
TIA
Vic
_____________________________________________________
Victor Fraenckel - The Windman vfraenc1@n...
KC2GUI
www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
12volt input
5volt output
500ma output current
I have been using the 7805 regulator for this but the heat output due
to the rather high differential voltage (7v) is not acceptable. I need
a more efficient solution which is easy to build and inexpensive. As a
calibration point my 7805 solution uses one regulator and two capacitors
on a 1.5" square PCB.
Is there a good solution to my requirements. I am using the 7805 solution
to power a Garmin 25 board. The board and power supply are mounted inside
an aluminum chassis box approximately 4" x 3" x 3". Because of the use,
both the G25 and the power supply must be enclosed. The 12volts comes
from the battery in my car. I am very concerned about the heat buildup
inside the box. I have bored some holes in the top of the box which helps
some. However, I believe that the real solution is to have a more efficient
power supply
Any suggestions or ideas would be gratefully appreciated. I would also
appreciate a copy (CC) of any response be sent to my Email addess.
TIA
Vic
_____________________________________________________
Victor Fraenckel - The Windman vfraenc1@n...
KC2GUI
www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
Comments
also a bit more expensive. Look also for PowerTrends products.
Two step series regulators ( 7809 and a 7805 ) will also help to
better distribute heat buildup.
ACJacques
Victorf wrote:
>
> I have a requirement for the following power supply:
>
> 12volt input
> 5volt output
> 500ma output current
>
> I have been using the 7805 regulator for this but the heat output due
> to the rather high differential voltage (7v) is not acceptable. I need
> a more efficient solution which is easy to build and inexpensive. As a
> calibration point my 7805 solution uses one regulator and two capacitors
> on a 1.5" square PCB.
>
> Is there a good solution to my requirements. I am using the 7805 solution
> to power a Garmin 25 board. The board and power supply are mounted inside
> an aluminum chassis box approximately 4" x 3" x 3". Because of the use,
> both the G25 and the power supply must be enclosed. The 12volts comes
> from the battery in my car. I am very concerned about the heat buildup
> inside the box. I have bored some holes in the top of the box which helps
> some. However, I believe that the real solution is to have a more efficient
> power supply
>
> Any suggestions or ideas would be gratefully appreciated. I would also
> appreciate a copy (CC) of any response be sent to my Email addess.
>
> TIA
>
> Vic
> _____________________________________________________
>
> Victor Fraenckel - The Windman vfraenc1@n...
> KC2GUI
> www.windsway.com
>
> Home of the WindReader Electronic Theodolite
> Read the WIND
I'm doing a project where a stamp and a small motor need to be
running 24/7 in an outdoor environment. Living as I do in southern
California, solar power seemed like an obvious solution. so I bought
a solar panel and a big 12v battery. Can I power the stamp with the
panel at the same time I'm charging the battery, then let the battery
supply the power at night? Can anyone point me in the right direction
for creating a hybrid battery/solar panel power supply?
Thanks,
Mark
you are working at so here is some general advice:
You can run the low power circuitry off the _battery_
when it is being charged by the solar panel [noparse][[/noparse]PV] AND
at night without switching; you'll need a 5 volt regulator.
There should be a blocking diode in series between the
PV and the battery [noparse][[/noparse]often these diodes are internal to
the panel - use a shottkey diode of a rating to handle
full panel current otherwise]. This diode restricts
dark hours reverse discharge from the battery to the PV.
Size the battery and panel in some reasonable way so that
the battery can store one or two days expected solar
input from the PV.
Limit the battery charging voltage with either a series
or shunt regulator since the open circuit voltage of the
PV is likely way higher than the battery should have
[noparse][[/noparse]17+ volts] and the PV will keep putting out current,
though less than at lower voltages. The PV can be looked
at like a poorly regulated current source; short circuit
current is not a great deal larger than operating voltage
output current - hence you can use a shunt regulator OK
if that looks like a good way to go. Pay attention to
power dissipated in regulators - current x volts = power
and if any of these products is large in your circuits you
need heat sinks on your regulators.
Hope this helps... premena
>>
Date: Tue, 8 May 2001 16:32:33 -0700
From: markallen <markallen@m...>
I'm doing a project where a stamp and a small motor need to be
running 24/7 in an outdoor environment. Living as I do in southern
California, solar power seemed like an obvious solution. so I bought
a solar panel and a big 12v battery. Can I power the stamp with the
panel at the same time I'm charging the battery, then let the battery
supply the power at night? Can anyone point me in the right direction
for creating a hybrid battery/solar panel power supply?
<<
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went wrong - the 5v regulator got really hot immediately and then my
circut blew out. I'm estimating the load is @600 ma and 4.5v. It's
powering a portable mp3 player. I'm estimating the load at that
because the wall wart that came with the mp3 player said that on the
outside. I hope this isn't too basic an electronics question...
>Mark, you didn't mention what power levels or amp hours
>you are working at so here is some general advice:
>
>You can run the low power circuitry off the _battery_
>when it is being charged by the solar panel [noparse][[/noparse]PV] AND
>at night without switching; you'll need a 5 volt regulator.
>
>There should be a blocking diode in series between the
>PV and the battery [noparse][[/noparse]often these diodes are internal to
>the panel - use a shottkey diode of a rating to handle
>full panel current otherwise]. This diode restricts
>dark hours reverse discharge from the battery to the PV.
>
>Size the battery and panel in some reasonable way so that
>the battery can store one or two days expected solar
>input from the PV.
>
>Limit the battery charging voltage with either a series
>or shunt regulator since the open circuit voltage of the
>PV is likely way higher than the battery should have
>[noparse][[/noparse]17+ volts] and the PV will keep putting out current,
>though less than at lower voltages. The PV can be looked
>at like a poorly regulated current source; short circuit
>current is not a great deal larger than operating voltage
>output current - hence you can use a shunt regulator OK
>if that looks like a good way to go. Pay attention to
>power dissipated in regulators - current x volts = power
>and if any of these products is large in your circuits you
>need heat sinks on your regulators.
>
>Hope this helps... premena
actually measure the current the device uses with an
ammeter. It's possible you connected the regulator wrong
way around or without in/out bypass capacitors [noparse][[/noparse]can cause
instability and self destruction] - see data sheet.
If you _did_ have .6 amps and a 14 volt input [noparse][[/noparse]charged
12 v battery] and 5 volts out that's .6x(14-5) = 5.4 watts
in the regulator which would certainly require a heat
sink on the TO-220 regulator!
BTW this would be a very inefficient way to run a PV panel
as most of the power would be lost as heat - solutions - either
use a lower voltage PV and 6 Volt battery or use a switching
regulator to drop to 5 v.
Power supplies are prosaic but required on most every project
so polish up your ohm's law and power calc skills :-) .
Good luck!
>>>
Date: Thu, 10 May 2001 17:45:35 -0700
From: markallen <markallen@m...>
Thanks for the thoughtful reply. I tried this before and something
went wrong - the 5v regulator got really hot immediately and then my
circut blew out. I'm estimating the load is @600 ma and 4.5v.
.....
>M
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writes:
> BTW this would be a very inefficient way to run a PV panel
> as most of the power would be lost as heat - solutions - either
> use a lower voltage PV and 6 Volt battery or use a switching
> regulator to drop to 5 v.
how about a pwm and a cap to fill in the lows.
I have recently bought a StampWorks kit, and I am
just getting started. My first problem is the power supply:
The kit provides a 120V->12V(1000mA) voltage transformer,
but in my country we have 220 Volts supply. So I cannot
use the transformer supplied with the kit, and a 220V->12V(1000mA)
transformer is not available in the local market.
So my question is: if I have to buy a new transformer, what is the
range of volts and Amps that it should supply? For example, is it
ok for me to use a 220V->12V(750mA) transformer?
Secondly, can I use a battery pack, like the one used in Boe-Bot?
If so, what are the battery specification?
Thanks a lot for your help,
- Raj
should be fine. Just make sure the outer portion of the connector is
ground. If you plan on running a couple of motors or other high current
devices a 1 amp transformer would be better. The board itself has a five
volt regulator already on it.
Original Message
From: "rsm_interraeda" <rsm@n...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, April 02, 2002 1:36 AM
Subject: [noparse][[/noparse]basicstamps] power supply question
> Hi,
>
> I have recently bought a StampWorks kit, and I am
> just getting started. My first problem is the power supply:
>
> The kit provides a 120V->12V(1000mA) voltage transformer,
> but in my country we have 220 Volts supply. So I cannot
> use the transformer supplied with the kit, and a 220V->12V(1000mA)
> transformer is not available in the local market.
>
> So my question is: if I have to buy a new transformer, what is the
> range of volts and Amps that it should supply? For example, is it
> ok for me to use a 220V->12V(750mA) transformer?
>
> Secondly, can I use a battery pack, like the one used in Boe-Bot?
> If so, what are the battery specification?
>
> Thanks a lot for your help,
>
> - Raj
>
>
>
> To UNSUBSCRIBE, just send mail to:
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>
>
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>
>
>
is it possible to make a DC power supply from a pc power supply?
a pc power supply is cheaper (maybe) than a transformer
and i do not have to worry about handling the transformer
so i can just connect from output wires of the power supply to the
board
it has three adjustable outputs (two of +24V(or less), -12V)
is it a good idea to do this?
please give me some opinions.
thanks
proper output wires and use it as is.
jim
http://www.geocities.com/jimforkin2003/
Original Message
From: i_drives [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=iL-78NTK2F73DFuP63lLw8HNaPFC35cSH3LcRGj86sVBjmwurqy_Pk75sUFotMNrlaf1Q144tpI]i_drives@y...[/url
Sent: Tuesday, December 02, 2003 2:22 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] power supply question
hi all
is it possible to make a DC power supply from a pc power supply?
a pc power supply is cheaper (maybe) than a transformer
and i do not have to worry about handling the transformer
so i can just connect from output wires of the power supply to the
board
it has three adjustable outputs (two of +24V(or less), -12V)
is it a good idea to do this?
please give me some opinions.
thanks
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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Of course, the price is right if you have some old PC's laying around ready
to be trashed. One thing to be aware of is that some switcher supplies need
a bit of a load to startup and regulate properly. So by putting a small load
resistor across each of the outputs (typically 5 volts, 12 volts, and minus
12 volts) you can make this work. Also, if memory servers, there's an extra
lead (orange I think), that's some sort of sensor lead that can shut down
the supply. I think it's for standby operation, but it's been a LOOOOONG
time since I've fooled with one of these.
Mike Sokol
www.modernrecording.com
mikes@m...
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: "i_drives" <i_drives@y...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, December 02, 2003 2:21 AM
Subject: [noparse][[/noparse]basicstamps] power supply question
> hi all
>
> is it possible to make a DC power supply from a pc power supply?
> a pc power supply is cheaper (maybe) than a transformer
> and i do not have to worry about handling the transformer
> so i can just connect from output wires of the power supply to the
> board
> it has three adjustable outputs (two of +24V(or less), -12V)
> is it a good idea to do this?
> please give me some opinions.
> thanks
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Just be sure to fuse it!
Regards,
Al Williams
AWC
* New kit: Read position data
http://www.al-williams.com/gp5.htm
>
Original Message
> From: i_drives [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=JaBxZq9Q8RvP4Ds97sjM1FFbesK29222PrhJx2xsRsTquRvAQxij0M-KNly_3nZePIBwfZmHrim0HX0]i_drives@y...[/url
> Sent: Tuesday, December 02, 2003 1:22 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] power supply question
>
> hi all
>
> is it possible to make a DC power supply from a pc power supply?
> a pc power supply is cheaper (maybe) than a transformer
> and i do not have to worry about handling the transformer
> so i can just connect from output wires of the power supply to the
> board
> it has three adjustable outputs (two of +24V(or less), -12V)
> is it a good idea to do this?
> please give me some opinions.
> thanks
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
but it could work. I do know that some of these early switchers wouldn't
start up and regulate without some sort of load. We used to test these in my
shop, and finally made a load plug for just such occasions. A few hundred
ohms across each supply couldn't hurt, and will serve to bleed down the
supply when its turned off. The 12 volt supplies with a 220 ohm bleeder will
draw a little over half-watt (12v x 12v / 220 ohm) = 0.654 watt. The 5 volt
supply with 100 ohms will draw 1/4 watt (5v x 5v / 100 ohms) = 0.25 watt.
Maybe the new switchers are more tolerant of no-load conditions, but if
you're pulling the power supply from a 10 year old junker computer, consider
adding a load.
Mike Sokol
www.modernrecording.com
mikes@m...
301-739-6842 (Office)
301-964-5682 (Mobile)
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: "Allan Lane" <allan.lane@h...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, December 02, 2003 1:22 PM
Subject: [noparse][[/noparse]basicstamps] Re: power supply question
> As Mike Sokol pointed out, some of these need
> a load resistor to start up properly.
>
> I thought it was only needed on the +5 volt line.
> Check with JDR Microdevices, or Jameco.
>
> --- In basicstamps@yahoogroups.com, markallen <markallen@m...> wrote:
> > Hi.
> >
> > I'm doing a project where a stamp and a small motor need to be
> > running 24/7 in an outdoor environment. Living as I do in southern
> > California, solar power seemed like an obvious solution. so I
> bought
> > a solar panel and a big 12v battery. Can I power the stamp with the
> > panel at the same time I'm charging the battery, then let the
> battery
> > supply the power at night? Can anyone point me in the right
> direction
> > for creating a hybrid battery/solar panel power supply?
> >
> > Thanks,
> >
> > Mark
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
It's been a while since I have posted here, but I have a question that
is just a tad off topic that I am sure someone here will have an
answer for, and I don't know where else to ask it.
My current project revolves around a solar system that I want to
operate a PC from. The solar system provides a +12V rail. I want to
run a PC from this system without using an inverter to power a normal
PC power supply.
After years of playing with basic stamps, I am used to +5VDC supplies,
the batteries supply a +12VDC supply, but I am just buggered how to
get -5VDC and moreover -12VDC .
I am sure that I am not the only person who needs to run a PC fron a
12VDC rail, so if there is anyone out there who can suggest an
appropriate circuit I would more than appreciate it.
Regards,
Dwain.
9volts it outputs everything you should
[url=need.http://www.mygizmos.net/frames/hardware/psu2-]need.http://www.mygizmos.net/frames/hardware/psu2-[/url]
5_schematic.pdf,the site should even have the board layout.Just do a
search on google for "Sproggy"
Hope it helps, Stan
--- In basicstamps@yahoogroups.com, "dwainsworld2000" <dwain@d...>
wrote:
> Hi Group,
>
> It's been a while since I have posted here, but I have a question
that
> is just a tad off topic that I am sure someone here will have an
> answer for, and I don't know where else to ask it.
>
> My current project revolves around a solar system that I want to
> operate a PC from. The solar system provides a +12V rail. I want to
> run a PC from this system without using an inverter to power a
normal
> PC power supply.
>
> After years of playing with basic stamps, I am used to +5VDC
supplies,
> the batteries supply a +12VDC supply, but I am just buggered how to
> get -5VDC and moreover -12VDC .
>
> I am sure that I am not the only person who needs to run a PC fron
a
> 12VDC rail, so if there is anyone out there who can suggest an
> appropriate circuit I would more than appreciate it.
>
> Regards,
>
> Dwain.