5v from a 9v battery
Simon Lebrun
I have a circuit I'd like to build that requires a 5v DC power supply.
I'd like to run it from a 9v battery. Can this be done by using a 5v
regulator (eg. 7805) on the 9v battery? Is it that simple?
Simon Lebrun
leb...@hwcn.org
--
Peter H. Anderson
yes .. you should have capacitors on the line and load side of the
regulator and a 1K resistor on the load side to maintain enough current to
keep the regulator turned on, but the 705 will do the job for you ..
--
Peter H. Anderson, p...@access.digex.net, http://www.access.digex.net/~pha
Parallel Port & Basic Stamp Control and Data Acquisition
Simon Lebrun <am...@freenet.hamilton.on.ca> wrote in article
<5hngl6$q...@main.freenet.hamilton.on.ca>...
: I have a circuit I'd like to build that requires a 5v DC power supply.
:
George W. marutz II
Simon,
Actually yes, it is that simple. The 7805 would definitely be the easiest
choice to implement for your needs, but, not necessarily the best choice.
The 7805 is an outdated device. It is inefficient and has a high
regulation cut-off voltage. Since the 7805 was introduced nearly thousands
of other choices have become available. I do not recommend the 7805 in
battery powered projects because the regulator itself will consume much of
your battery just in regulating the voltage to 5V!!!
Try looking at National Semiconductors or Linear Technologies web sites for
other options. You do not need anything fancy, just something geared
towards battery powered projects. They should be good at helping you make
a selection.
This may be more than you are willing to go into but have you considered a
switching power supply? Switchers will perform the same function as your
linear 7805 and be a heck of a lot more efficient. Once again, look to
conserve battery power.
Hope I could help
George...
Gareth Baron
In article <01bc3dd8$ed717fc0$52c0...@teleweb.teleweb.net>, "George W.
marutz II" <gma...@teleweb.net> writes
>Simon,
>
>Actually yes, it is that simple. The 7805 would definitely be the easiest
>choice to implement for your needs, but, not necessarily the best choice.
>
>The 7805 is an outdated device. It is inefficient and has a high
>regulation cut-off voltage. Since the 7805 was introduced nearly thousands
>of other choices have become available. I do not recommend the 7805 in
>battery powered projects because the regulator itself will consume much of
>your battery just in regulating the voltage to 5V!!!
>
>Try looking at National Semiconductors or Linear Technologies web sites for
>other options. You do not need anything fancy, just something geared
>towards battery powered projects. They should be good at helping you make
>a selection.
>
>This may be more than you are willing to go into but have you considered a
>switching power supply? Switchers will perform the same function as your
>linear 7805 and be a heck of a lot more efficient. Once again, look to
>conserve battery power.
>
are interested in this design route.
>Hope I could help
>
>George...
>
>
>
>
>
>
>Simon Lebrun wrote:
>
>> I have a circuit I'd like to build that requires a 5v DC power supply.
>> I'd like to run it from a 9v battery. Can this be done by using a 5v
>> regulator (eg. 7805) on the 9v battery? Is it that simple?
>>
>> Simon Lebrun
>> leb...@hwcn.org
>>
>> --
>>
Gareth Baron
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Peter Bennett
Simon Lebrun wrote:
>
> I have a circuit I'd like to build that requires a 5v DC power supply.
> I'd like to run it from a 9v battery. Can this be done by using a 5v
> regulator (eg. 7805) on the 9v battery? Is it that simple?
>
> Simon Lebrun
> leb...@hwcn.org
Yes, that would work, if the current requirement is small (under 50 mA,
preferably much under!, depending on the battery life you require).
An alternative for more current (and assuming your circuit isn't too
fussy about voltage) is to use four 1.5 cells - AA, C or D depending on
current and required battery life.
This will give 6 volts when the batteries are fresh, so I would add a
power diode, such as 1N4001, in series to drop 0.7 volts, if your
circuit won't tolerate 6 V.
--
Peter Bennett VE7CEI ben...@triumf.ca
TRIUMF, Vancouver, B.C., Canada
GPS and NMEA info and programs:
ftp://sundae.triumf.ca/pub/peter/index.html or
ftp://ftp-i2.informatik.rwth-aachen.de/pub/arnd/GPS/peter/index.html
or http://vancouver-webpages.com/peter/index.html
John Shadrach
Yes it is that easy, providing you don't want to draw too much current.
Also golden rule with alkaline batteries is to put 220 to 470 microfarad
capacitor across them to handle transients, plus 0.1 or similar on input
and output of regulator, close to package, to stop dreaded oscillations.
78L05 might also be more appropriate.
John Shadrach
Simon Lebrun <am...@freenet.hamilton.on.ca> wrote in article
<5hngl6$q...@main.freenet.hamilton.on.ca>...
> I have a circuit I'd like to build that requires a 5v DC power supply.
> I'd like to run it from a 9v battery. Can this be done by using a 5v
> regulator (eg. 7805) on the 9v battery? Is it that simple?
>
> Simon Lebrun
> leb...@hwcn.org
>
> --
>
pspray
Try the LM2931-5.0 from National. I specified it in a battery powered
device. I think its quiescent current is only about 1 mA. Anyhow, it's
the lowest Iq device I could find. I wasn't concerned with dropout since
the supply in this case was 12 V and the other stuff would not work if the
battery got anywhere close to the dropout point of the 2931.
-- pHil
>Try looking at National Semiconductors or Linear Technologies web sites for
>other options. You do not need anything fancy, just something geared
>towards battery powered projects. They should be good at helping you make
>a selection.
>> I have a circuit I'd like to build that requires a 5v DC power supply.