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Which power supply should I use? Answered

I have a Velleman kit that doesn't come with a power supply. The specifications say to use a 9v 150mA DC adapter but I am having trouble find a wall plug like this. Could I use a 9v 200mA wall adapter or maybe a 9v battery pack without damaging it?

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icengBest Answer (author)2012-11-15

YES .... of course you can use wall adapter with a higher current capacity
as long as it is 150 ma or more.

Iv built Velleman kits and can tell you this one and others are well designed 
to be insensitive to input supply variations..

This would be hard to be damaged as long as you don't exceed 10v
And don't worry about under power because the unit would simply not
work until about 8.5v and 150ma up to 10v and 500ma or more .

A

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Arya42 (author)iceng2012-11-16

Thanks. Could I also use a 9v battery pack?

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steveastrouk (author)Arya422012-11-16

No, because you can't get enough current out of a 9V rectangular battery

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Arya42 (author)steveastrouk2012-11-16

Why not? Isn't there about 600mA in a fully charged 9v battery and it needs to be at least 150mA?

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steveastrouk (author)Arya422012-11-16

You're confusing output current, which is in Milli amps with capacity, which had the units of miliampere_ hours. Capacity is energy storage, but you can only get that out at a limited rate.

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Arya42 (author)steveastrouk2012-11-16

So that's what it means when it says mAh on a battery?

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steveastrouk (author)Arya422012-11-16

Yes. "600mAhr", means you can theoretically pull 600mA for one hour, and then its empty. In fact, you can't discharge a battery at that rate and get that much energy, they are actually rated over 10 hours, so a 600mAhr battery can deliver 60mA for 10 hours.

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iceng (author)steveastrouk2012-11-16

+1
square 9v batteries are a limited power source
you could not run an electric scooter on it.

But mixing a square 9v battery with pocket change will burn up the battery ( get hot ) when a coin shorts it out ..

Also incidentally it got rather uncomfortable in my pants at the Coffey shop some years ago.

The point being the energy in a new battery when suddenly released did not even burn the skin or harm the fabric.

Point being ;  that the energy storage isn't all that much in a non-Lithium battery.

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steveastrouk (author)iceng2012-11-16

Why are we getting so many questions about PSU output current ATM ?

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Re-design (author)steveastrouk2012-11-16

Steve why don't you create and info/instructable on power supply basics? Then we can point them to that to get the whole story instead of just the rough edges.

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steveastrouk (author)Re-design2012-11-16

Trouble is, its really a "guide", but "guides" are supposed to be lists of instructables.

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steveastrouk (author)Re-design2012-11-16

Yeah sounds like a plan for a collaborative effort.

Steve

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