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Topic: Will I need voltage regulator (like LM7805) for 'stabilized' PSU (Read 3636 times) previous topic - next topic

artvolk

Good day!

I've power brick which 5V output and it seems to be 'stabilized' will I need a further voltage regulation, or I can connect ATmega MCU directly to it? Does 'stabilized' mean 'voltage regulator built-in'?

P.S. It seems that LM7805 will not work in such situation anyway, because it have 2V dropout.

Thanks!

You don't actually need to supply regulated voltage. If you supply the 5V on the Vin Pin, there's an on-board regulator that gives you a regulated +5V output on the 5V power pin of the arduino while powering the arduino itself.
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James C4S

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If you supply the 5V on the Vin Pin, there's an on-board regulator that gives you a regulated +5V output on the 5V power pin of the arduino while powering the arduino itself.

This is not correct.  While it is true there is an on-board regulator, it will not reliably work if given 5V in.  The on-board regulator (like the 7805) really needs about 2V and so Vin should be at least 7V.

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I've power brick which 5V output and it seems to be 'stabilized' will I need a further voltage regulation

Generally power bricks are regulated.  However, they also tend to be switching power supplies which may have a minimum load requirement.  In other words, they are regulated provided enough current is being drawn.  One simple measurement is to measure its no-load voltage.  If it is 5V you should be fine.  If it goes higher than that, you might need to do more investigating.
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artvolk

It seems I was no clear in first post -- I'm powering bare ATmega chip, not Arduino board (which have regulator build-in).

James, thanks for the response, I will try to measure open circuit voltage (without load).

James C4S

You will still want to provide some local (close to the chip) de-coupling capacitors.  It will help stabilize ripple-voltage.
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artvolk

Thanks for the tip, I've standard 0.1uF and 47uf decoupling capacitors on all ICs, is this what do you mean?

James C4S

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westfw

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it seems to be 'stabilized'

So you want us all to guess what "stabilized" might mean when used by the particular manufacturer of your supply?
It MIGHT mean the same as "regulated", and it might not (it could mean that it's just filtered DC, for instance.)  You pretty much need to measure it to find out...

artvolk

It seems that this is a translation issue from Russian, I should call it "regulated" in English. I've opened the case of this particular supply and it has LM78xx regulator on the output. I've also measured open circuit voltage (without load) and it is the same as nominal value.

Grumpy_Mike


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