Current rating of power supply - Electronic Circuits Projects Diagrams Free

shiv · 27th May 2003, 03:30 AM

Hi
i use 5V,10mA supply. For some special cases, 30mA current rating is required and i can use only one 5V,10mA supply. How can 30mA be accomodated with 5V,10mA power supply?

Thanks
Shiva

stevez · 27th May 2003, 11:33 AM

The short answer is that it can't.

Your 10 ma supply may be grossly under-rated and/or the 30 ma requirement is an overstatement. Without a lot more information about the supply and load it's tough to comment.

Gene · 27th May 2003, 11:15 PM

steve is right. I would re-build it into a 30ma supply which would be strong enough to handle either application.

stevez · 28th May 2003, 05:02 PM

Worth mentioning is that a power supply (like anything else) is only as strong as it's weakest link. Sometimes careful examination of the components will reveal an opportunity to get more out of something - but only sometimes.

Sometimes we get by in connecting a 30 ma load to a 10 ma supply because the 30 ma represents a peak that is seldom reached and the 10 ma is a continuous rating. Sometimes we can make the 10 ma supply work by not pushing whatever it is so hard. An example might be a 300 watt amplifier that we might want to run on a power supply that falls short of requirements - we might simply limit how far up we turn the volume as a way of managing the inadequate supply.

Transformers are one of several components that can be stretched, so to speak. I know that a transformer designed for continuous commercial service can be used at levels twice it's design if used in intermittent amateur service. It really doesn't put out any more - it's just that we've put it to work in a situation that is less demanding.

Wire is another one of those where how much current it can carry depends on a number of things. A 12 ga wire in a conduit is rated at less current than one in open air - presuming of course that voltage drop isn't the issue.

Sometimes the answer is "try it and see" but this applies only if the result of failure is acceptable - not a fire, injury, death, costly, etc.

So the short answer is still "no" but I've offered a little more.

27th May 2003, 03:30 AM	(permalink)
shiv New Member	Current rating of power supply Hi i use 5V,10mA supply. For some special cases, 30mA current rating is required and i can use only one 5V,10mA supply. How can 30mA be accomodated with 5V,10mA power supply? Thanks Shiva

27th May 2003, 11:33 AM	(permalink)
stevez Experienced Member	The short answer is that it can't. Your 10 ma supply may be grossly under-rated and/or the 30 ma requirement is an overstatement. Without a lot more information about the supply and load it's tough to comment. __________________ stevez

28th May 2003, 05:02 PM	(permalink)
stevez Experienced Member	Worth mentioning is that a power supply (like anything else) is only as strong as it's weakest link. Sometimes careful examination of the components will reveal an opportunity to get more out of something - but only sometimes. Sometimes we get by in connecting a 30 ma load to a 10 ma supply because the 30 ma represents a peak that is seldom reached and the 10 ma is a continuous rating. Sometimes we can make the 10 ma supply work by not pushing whatever it is so hard. An example might be a 300 watt amplifier that we might want to run on a power supply that falls short of requirements - we might simply limit how far up we turn the volume as a way of managing the inadequate supply. Transformers are one of several components that can be stretched, so to speak. I know that a transformer designed for continuous commercial service can be used at levels twice it's design if used in intermittent amateur service. It really doesn't put out any more - it's just that we've put it to work in a situation that is less demanding. Wire is another one of those where how much current it can carry depends on a number of things. A 12 ga wire in a conduit is rated at less current than one in open air - presuming of course that voltage drop isn't the issue. Sometimes the answer is "try it and see" but this applies only if the result of failure is acceptable - not a fire, injury, death, costly, etc. So the short answer is still "no" but I've offered a little more. __________________ stevez

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27th May 2003, 11:15 PM	(permalink)
Gene Experienced Member	steve is right. I would re-build it into a 30ma supply which would be strong enough to handle either application.