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Topic: Do any clone Pro Minis actually come with a power isolation jumper? (Read 474 times) previous topic - next topic

ShermanP

What I believe is the official Arduino schematic for the (Sparkfun) Pro Mini shows a power isolation jumper which if opened lets you power the Vcc pin directly without any current flowing back through the regulator to ground, and it also isolates the power LED.  I ordered my first 3.3V 8MHz Pro Mini, and it seems to work fine, but alas, no power isolation jumper.  I didn't realize I had to check for that.

I'm going to run the processor directly on an unregulated 18650, and the jumper would have been convenient to have.  As it is, I'll have to desolder or cut the output pin of the regulator, as well as the power LED or its resistor in order to minimize power loss.  The device will be in deep sleep most of the time, but there's no power switch.  The schematic for the regulator shows a resistor divider from the output to ground, which provides feedback for the regulator.  So clearly I need to prevent that flow from taking place.  And of course we can't be having no stinking power LED.

For future reference, does anyone know of a source of clone Pro Minis which do have the jumper, or is that only available in the Sparkfun model?

jremington

For low power or battery operation of the Pro Mini or clones, I just remove the regulator and the LED resistor, with a short swipe of a hot solder pencil tip. Takes about 5 seconds. Then it can be powered through Vcc with any voltage above 1.8V (although 16 MHz operation generally requires at least 4.0V).

An "official" Arduino schematic would be obtained from Arduino, not Sparkfun.

pert

An "official" Arduino schematic would be obtained from Arduino, not Sparkfun.
The Arduino Pro Mini was designed, manufactured, and sold by SparkFun. They were sold in the Arduino Store for a while (just as Arduino sells Paul Stoffregen's Teensy boards in the Arduino Store now), but these were still Sparkfun boards, with the SparkFun logo on them:

So the SparkFun Pro Mini schematic is the official schematic.

wvmarle

a power isolation jumper
I've never seen this on my Pro Mini (clone) boards. Care to share a link to that schematic? Which exact jumper (reference number) would be this power isolation?
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

jremington

Pert, thanks for providing that fascinating factlet!

Could you take a moment to answer the OP's question, about why the power jumper shown on the official schematic seems to be missing?

6v6gt

Well, here is the 'power' jumper (SJ1 in the schematic). It is on the left hand side but to the right of the GND and RST pins. It looks like a blob of solder.




Picture from: https://www.sparkfun.com/products/11114

There are also 2 jumpers on the reverse side near A4 and A5 but these are for the I2C pull up resistors.

Of course, other versions and their clones may have a different layout.

ShermanP

It was pretty easy to remove the regulator and the power LED's resistor.  But this is a one-way modification, so there's no practical way of going back.  The good thing about the jumper is that you don't have to remove any parts, and can restore the solder blob to restore the regulator and power LED if you wanted to do that for some reason.

So now the Atmega does the power-down sleep at something under 0.5 uA.  Actually, I don't have a digital meter that goes that low, but my trusty ancient analog meter has a 50uA scale, and the needle just barely moves.  Youtube videos on this general subject show a power-down sleep current of 0.3 to 0.4 uA.  That's provided you do all the things needed to minimize current during sleep.

My original question was whether anyone knows of a clone pro mini which has the jumper.  So far it appears that may not exist.

jremington

Pro Mini clones cost only about $1 on eBay, and they always seem to work, so just buy several and modify them any way you like. Pick up a few of the 3.3V version while you are at it, as they eliminate the hassle of interfacing to 3.3V sensors.

That way there is never a need to "reverse" a modification, and you are pretty likely to destroy one or two anyway. I certainly have.

pert

I have about 5 different styles of Pro Mini derivatives. I just took a look and found that none of them have this jumper. It's a bit surprising to me. I'm very surprised that all these manufacturers took the time to develop their own designs, rather than just grabbing SparkFun's Eagle files. The only thing I can think is that there was something about SparkFun's design that made it more expensive or difficult to manufacture. While they were at the redesign, they went ahead and removed anything they thought was unnecessary.

I'm actually not a big fan of the SparkFun style of Pro Mini. I really like the Chinese ones that have all pins on grid and even manage to squeeze in an ICSP header! That's the only style I'll buy now.

Paul__B

Pro Mini clones cost only about $1 on eBay,
Well, maybe just a little more than that!  :smiley-roll:

6v6gt

. . .
I'm actually not a big fan of the SparkFun style of Pro Mini. I really like the Chinese ones that have all pins on grid and even manage to squeeze in an ICSP header! That's the only style I'll buy now.
I agree about the non-prototype board friendly spacing of the pins, especially A4 to A7, but can you provide a link to a clone which does use exclusively a 0.1 inch matrix.

pert

OK, I exaggerated about "all pins on grid". The "FTDI header" is not on grid. That doesn't bother me because I don't ever need to connect that to a prototype board.

https://www.ebay.com/itm/352036437846


I think you can find them a little cheaper on Aliexpress, but I've been burned too many times now by the horrible sellers on that site so I've decided I'd rather just pay a bit more on eBay and actually get my orders.

6v6gt

OK, I exaggerated about "all pins on grid". The "FTDI header" is not on grid. That doesn't bother me because I don't ever need to connect that to a prototype board.

https://www.ebay.com/itm/352036437846


I think you can find them a little cheaper on Aliexpress, but I've been burned too many times now by the horrible sellers on that site so I've decided I'd rather just pay a bit more on eBay and actually get my orders.
That is great. Thanks. The FTDI header of course does not matter because that is connected directly to the programmer as required. That retailer does not ship here, but it has given me hope.

pert

You're very welcome. There are definitely other sellers of this style of Pro Mini. That was just the first result in my "price + shipping low to high" search.

Unfortunately, this style of board doesn't seem to be quite so common as the other ones, and is not the cheapest option. I'm not sure why more sellers aren't using this one. It was even featured in a Hackaday article a while back talking about how great the design is.

The button is a little close to the ICSP through holes to fit a male header, but I only needed to trim the edge of the header plastic a little bit to fix that; only takes a few seconds. I actually usually don't bother with the male header for ICSP because I am normally incorporating these boards into finished projects where I rarely need to flash the firmware, so I just press my pogo ICSP adapter down on the holes when I do want to program them.

ShermanP

pert, what are the 10 pins on the left that aren't on the main DIP lines?  I assume A4-A7 are there, but what else?  I tend to breadboard everything, at least in the beginning, so the non-DIP-line holes aren't particularly useful.

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