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Nano on-board regulator...was: I made a mistake

 

Hi Dale,

I'm designing a NANO project right now that uses the on-board regulator at about +12v input. I'm only powering the atmega328p chip and? 6 digital outputs, consisting of low-current LEDs/opto-isolators. I've had no problems, so far, with a random sampling of about a dozen cheapo boards....My max current draw is perhaps 25mA. How much current were you drawing from the regulator where it popped??

....Now I'm concerned that I may need to consider an external regulator.

Thanks,

73, David KB4FXC
 

On the raduino, the si5351 is sucking as much as 35ma+5.6ma=40.6ma of 3.3v from the Nano assembly
as per table 3 on p5 of ?https://www.silabs.com/documents/public/data-sheets/Si5351-B.pdf
That 3.3v comes from a regulator tucked inside the USB chip at U2, whatever the clones are stuffing there.
? ??
That's a very significant extra load on U2.

The USB chip at U2 is powered from the Nano's 5v rail which could come from 12v vin through the
dinky 5v regulator at U3, though on the Raduino we instead have a separate 5v LM7805 in a TO220. ?
The Raduino's TO220 can get quite hot.
The Raduino would likely blow U3 if it didn't have a separate TO220 LM7805,
even if U3 was an honest ua78m05 in the sot223

Unless shaving pennies, I'd tend to just feed the Nano 5v and not borrow any 3.3v from it.
Especially if getting pot-luck Nano clones from Ebay.


On Sun, Oct 22, 2017 at 02:11 pm, David McGough wrote:
I'm designing a NANO project right now that uses the on-board regulator at about +12v input. I'm only powering the atmega328p chip and? 6 digital outputs, consisting of low-current LEDs/opto-isolators. I've had no problems, so far, with a random sampling of about a dozen cheapo boards....My max current draw is perhaps 25mA. How much current were you drawing from the regulator where it popped??

....Now I'm concerned that I may need to consider an external regulator.
 

David KB4FXC

Regardless of what has been said about the on-board regulator being questionable, it is a pretty
standard 3-terminal regulator it is usually good for at least 100 ma.? I have used a couple dozen
of the Asian manufactured NANO boards with +13.6 volts input and they all worked just fine.??

I suspect that your concern about exceeding current limits may be valid though because there is
no heat sink on those on-board regulators.? Most of my Arduino based test equipment uses the
on-board regulator for NANO and an attached LCD.? Other circuitry is powered from a 7805L or
higher current capable 7805 equivalent.?

There is a lot of not-invented-here and not-manufactured-here sentiment among the ham radio
fraternity.? Some of it justified and some is just myth and FUD (Fear, Uncertainty, and Doubt).

Arv? K7HKL
_._


On Sun, Oct 22, 2017 at 3:11 PM, David McGough <kb4fxc@...> wrote:
Hi Dale,

I'm designing a NANO project right now that uses the on-board regulator at about +12v input. I'm only powering the atmega328p chip and? 6 digital outputs, consisting of low-current LEDs/opto-isolators. I've had no problems, so far, with a random sampling of about a dozen cheapo boards....My max current draw is perhaps 25mA. How much current were you drawing from the regulator where it popped??

....Now I'm concerned that I may need to consider an external regulator.

Thanks,

73, David KB4FXC


 

Hi Arv,

Thanks for the comments. The Nano's I've got have a (clone, I'm sure)
AM1117-5.0 regulator. I noticed the datasheet says the ABS MAX input
voltage is 15VDC, a stark contrast to 26+ VDC MAX for LM2940 in the
"stock" Nano design, or even the 35VDC limit for 78xx series regulators.

I'll do some additional testing and make sure "LDO" doesn't stand for Low
Dropout OSCILLATOR! HiHI.

73, David KB4FXC

On Sun, 22 Oct 2017, Arv Evans wrote:

David KB4FXC

Regardless of what has been said about the on-board regulator being
questionable, it is a pretty
standard 3-terminal regulator it is usually good for at least 100 ma. I
have used a couple dozen
of the Asian manufactured NANO boards with +13.6 volts input and they all
worked just fine.

I suspect that your concern about exceeding current limits may be valid
though because there is
no heat sink on those on-board regulators. Most of my Arduino based test
equipment uses the
on-board regulator for NANO and an attached LCD. Other circuitry is
powered from a 7805L or
higher current capable 7805 equivalent.

There is a lot of *not-invented-here* and *not-manufactured-here* sentiment
among the ham radio
fraternity. Some of it justified and some is just myth and FUD (Fear,
Uncertainty, and Doubt).

Arv K7HKL
_._


On Sun, Oct 22, 2017 at 3:11 PM, David McGough <kb4fxc@...> wrote:

Hi Dale,

I'm designing a NANO project right now that uses the on-board regulator at
about +12v input. I'm only powering the atmega328p chip and 6 digital
outputs, consisting of low-current LEDs/opto-isolators. I've had no
problems, so far, with a random sampling of about a dozen cheapo
boards....My max current draw is perhaps 25mA. How much current were you
drawing from the regulator where it popped??

....Now I'm concerned that I may need to consider an external regulator.

Thanks,

73, David KB4FXC
 

There are clearly a few items of ebay electronics about which some fear, uncertainty and doubt is in order.

For example, good luck getting 20 AH at 12v out of this:
? ?

Or getting the maximum rated amps out of any $2 switching (or linear) power supply
across the entire claimed input and output voltage ranges. ?Or even half of the rated amps.
For more than a few milliseconds.

Ebay RD16HHF1 RF power FET's are often some random switcher FET with fresh ink.
That can even happen with the relatively cheap IRF510, why anybody would bother is beyond me.

But many have had surprisingly good luck with the $3 Nano's.
Including most Bitx40 owners.
Though they must be cutting corners where they can off the design of the $30 original.
?
And I did just order 50pcs of the AD8307 for less than I could get two out of Mouser
as per the last paragraph of this post: ?/g/BITX20/message/32675
Got my fingers crossed.

Jerry


On Sun, Oct 22, 2017 at 02:40 pm, Arv Evans wrote:
Regardless of what has been said about the on-board regulator being questionable, it is a pretty
standard 3-terminal regulator it is usually good for at least 100 ma.? I have used a couple dozen
of the Asian manufactured NANO boards with +13.6 volts input and they all worked just fine.??

I suspect that your concern about exceeding current limits may be valid though because there is
no heat sink on those on-board regulators.? Most of my Arduino based test equipment uses the
on-board regulator for NANO and an attached LCD.? Other circuitry is powered from a 7805L or
higher current capable 7805 equivalent.?

There is a lot of not-invented-here and not-manufactured-here sentiment among the ham radio
fraternity.? Some of it justified and some is just myth and FUD (Fear, Uncertainty, and Doubt).
 

Hi Jerry,

I know all ebay switchers aren't equal, of course. But, here are some
cheapo examples that are success stories; with hundreds deployed in the
hamvoip.org project, etc.

At less than $0.80 each, these little boards are fantastic. The 3A rating
is intermittent duty cycle, efficiency is excellent, and protected from
output short-circuit/overload:

I power Raspberry Pi 3 boards, etc., from these. They don't skip a beat:



I agree that you should stay away from ebay RF power transistors unless
you're certain about the reseller/manufacturer. I, too, have purchased
some lemons!



73, David KB4FXC

On Sun, 22 Oct 2017, Jerry Gaffke via Groups.Io wrote:

There are clearly a few items of ebay electronics about which some fear, uncertainty and doubt is in order.

For example, good luck getting 20 AH at 12v out of this:
?? ?? ( )

Or getting the maximum rated amps out of any $2 switching (or linear) power supply
across the entire claimed input and output voltage ranges. ??Or even half of the rated amps.
For more than a few milliseconds.

Ebay RD16HHF1 RF power FET's are often some random switcher FET with fresh ink.
That can even happen with the relatively cheap IRF510, why anybody would bother is beyond me.

But many have had surprisingly good luck with the $3 Nano's.
Including most Bitx40 owners.
Though they must be cutting corners where they can off the design of the $30 original.
??
And I did just order 50pcs of the AD8307 for less than I could get two out of Mouser
as per the last paragraph of this post: ??/g/BITX20/message/32675 ( /g/BITX20/message/32675 )
Got my fingers crossed.

Jerry

On Sun, Oct 22, 2017 at 02:40 pm, Arv Evans wrote:


Regardless of what has been said about the on-board regulator being
questionable, it is a pretty
standard 3-terminal regulator it is usually good for at least 100 ma.?? I
have used a couple dozen
of the Asian manufactured NANO boards with +13.6 volts input and they all
worked just fine.????


I suspect that your concern about exceeding current limits may be valid
though because there is
no heat sink on those on-board regulators.?? Most of my Arduino based test
equipment uses the
on-board regulator for NANO and an attached LCD.?? Other circuitry is
powered from a 7805L or
higher current capable 7805 equivalent.??


There is a lot of not-invented-here and not-manufactured-here sentiment
among the ham radio
fraternity.?? Some of it justified and some is just myth and FUD (Fear,
Uncertainty, and Doubt).
 

Good steers!
Thanks.


On Sun, Oct 22, 2017 at 04:37 pm, David McGough wrote:
At less than $0.80 each, these little boards are fantastic. The 3A rating
is intermittent duty cycle, efficiency is excellent, and protected from
output short-circuit/overload:

I power Raspberry Pi 3 boards, etc., from these. They don't skip a beat:
 

I have tried several of the small switcher regulators, but in most cases I had to add additional filtering to reduce noise. When I have to run a Nano or pro-mini with more than about a 9V, I just feed it through several 1N4002 diodes in series to drop the applied voltage down to the 7-9 volt range. This makes the little regulator on the Nano or Pro-mini much happier.



--
DuWayne? KV4QB

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