Suppling power to MM

Sun May 07, 2017 6:53 pm

i would like to be sure about how to correctly supply my maple mini.
from Vin it goes to the ams1117
from the USB it goes to the ams1117
from Vcc directly to the stm32

about cross-supplying (not sure if it is the correct word) i see a diode marked S4 near the LDO so i would say it is a Schottky diode. Does it work as in the arduino? so i can supply the board at the same time from the usb and the Vcc or Vin?

could someone confirm this?

EDITED with corrections in the next posts

Mon May 08, 2017 8:45 am
aster wrote:from the USB directly to the stm32 (correct?)

Mon May 08, 2017 8:56 am
maple mini VIN (before pin 0) is 5v, before the LDO, hence my guess is it may be possible to connect 4xAA or AAA batteries (6v) at VIN, but do check the schematics & review your board (just in case those baite mini may be different) … lemini.pdf
i’ve been thinking about 4x NIMH 1.3v batteries as well giving a nice 5.2v when fully charged

incidentally i (ab)used that VIN on my baite mini, used it as ‘vout’ & routed it to supply my ILI9341 lcd board which has a separate LDO taking 5v VIN :lol:

note VCC is 3v3, 3.3v connecting anything higher may see the mini ‘blow up’ in smoke :twisted:

i’m thinking maple mini can possibly run on 2xAA or 2xAAA 1.5v batteries simply connecting them at VCC, 3V3, no regulators etc !

Mon May 08, 2017 9:24 am
It may also be possible to run the MM directly, without the voltage regulator on one 18650 (or any similar single LiPo/LiIon cell), with a suitable diode in series to keep the maximum voltage within the acceptable range of the datasheet i.e. < 4.0V … or perhaps even without the diode, although since a fully charged LiPo is around 4.2V that may be pushing your luck in terms of smoke production :?

Mon May 08, 2017 9:30 am
lipo is a ‘headache’ for me as it seemed 4.2v looks too low for the LDO, but too high for the mini, it is leaving me wondering what to do about those 4.2v lipo batteries, but i really would like to use those as if i use 2×1.5 v AA or AAA, i’m not sure how many of those AA or AAA batteries i’d need to send to the recyclers/garbage collectors a year :lol:

maybe i should try 4.2v lipo at the LDO VIN after all
has a 1.1 – 1.3v dropout, so 4.2v fully charged may give 2.9v to the mini, and if the battery drain a little, how long would the mini last :? or maybe i should try those big fat regulator diodes with at least 0.6v voltage dropout :lol:

Mon May 08, 2017 9:41 am
i’ve run maple mini’s from lithium batteries, and that worked pretty well, but it would indeed be nice to have a proper test on how well it works.

We’ve got 2 things that work to our advantage:
-the AMS1117’s dropout voltage mentioned in the datasheet is at 800mA, usually when using a maple mini, you’re probably even having a hard time reaching 100mA, so the dropout voltage should be far less (but i don’t find a graph on this in the datasheet, so we’d have to measure it)
-the maple mini (and most things you can connect to it), will cope with slightly lower voltages. if it were to drop down to 3V when the battery is running low, it’s very likely that everything will still work :).

Seems like an interesting thing to test :).

Mon May 08, 2017 9:57 am
stevestrong wrote:aster wrote:from the USB directly to the stm32 (correct?)

Mon May 08, 2017 10:00 am
do review the schematics … lemini.pdf
and have a volt / multimeter handy & measure voltages at the VIN (5v), VCC (VCC is 3V3) pins in the normal running mode
otherwise u may be taking some chances with magic smoke :lol:

Mon May 08, 2017 10:06 am
Since you can get a 5V boost regulator for less than a buck (pun intended), you could boost the lipo to 5v, then run the board from that. Not the most efficient method, but it has some advantages. … 5v&_sop=15

Mon May 08, 2017 10:24 am
this is a somewhat ‘crazy’ world, do a charge pump double the v say 4.2v – 8.4v, then put a regulator to get 5v, then do another LDO to get 3.3v

i’m not too sure if putting a 1 watt 5 ohm resistor in *series* at VCC (3v3) and connect 4.2v LIPO would be a ‘cheap & good’ solution though :lol:

my guess is perhaps we’d 1st try put that lipo at 4.2v so that with AMS1117′ dropout voltage is 1.1v – 1.3v, we’d get 2.9 v or 3.1v(optimistic) fully charged, then we play labamda & see how low can stm32 runs for under 3v, ADC may give goofy values though :lol: … 164185.pdf
page 7 1.2 Power supply schemes
The circuit is powered by a stabilized power supply, VDD .
– If the ADC is used, the V DD range is limited to 2.4 V to 3.6 V
– If the ADC is not used, the VDD range is 2.0 V to 3.6 V

ok i’m going to try running mini on lipo 4.2v over VIN & ams1117 LDO :D

btw did a little research on ebay about LDO, it seemed those ams1117 ‘flooded’ the mkt, probably a most common 3.3v ldo found in all the cheap consumer electronics & the baite mini (may be bluepill as wll) … 7&_sacat=0
i hardly think those tiny ams1117 are rated for 1amp, if u need anything close to 1 amp, the big LM1117 is probably needed … 1617053651

then i found the *real* li-po LDO, LP2950, just that it only gives a measly 100ma, but the dropout voltage is a nice 450mv max, so with LiPo with 4.2v – 0.45 ~ 3.75 that’s still plenty of headroom above 3.3v and u’d be able to spent all that battery juice till u are left with 2v on the stm32 … 50&_sop=15

and if 100ma is too measly small for the purpose after all we power gigabytes sd cards (never mind stm32f1 only has 20k sram & 128k flash) plus run the 72mhz cpu and then maybe run an lcd display board as well there is the more expensive mcp1700 LDO which gives 200-250ma … 01826C.pdf … 00&_sop=15

and if all else fails, then u’d go for LM1117 the big 1 which give 800ma or AMS1117 1A (can’t be those tiny ones) but now the dropout voltage is a whopping 1 – 1.3 v (btw all the other esoteric LDOs that may be found on sites like ti … either never appeared on ebay or is super expensive)

oh btw then as like ahull’s solution there is the state-of-the-art switch mode boost DC-DC converters these would drive that 1A x 5V (5 watts!) from that little 4.2v lipo battery … 21&_sop=15

Mon May 08, 2017 6:18 pm
i just did a measurement on the maple mini of the voltagedrop of the ams1117, and it’s indeed always >1V, even at lower current, so indeed a pretty crappy regulator if you want to run of lipo/lion

i’ve found similar regulators as ag123, and ordered
-some mcp1700’s
-some XC6206’s: 0.5A, 200mV drop @ 100mA
-some AP2112’s, up to 0.6A, max 250mV drop :).

enough to last me a while, and should all 3 suffice for powering our lovely devices from a lithium battery :).

Fri Oct 13, 2017 9:40 pm
Posting a little update to this topic: as i was ordering pcb’s anyway, i made some small adapters for AMS1117 -> AP2112K. See the result below (yeah, crappy soldering, i know :p ).

mm-ap2112k.jpg (67.75 KiB) Viewed 471 times

Sat Oct 14, 2017 1:57 am
aliexpress – only available in lots of 100, pricing £5.85 to £7.06 from 5 sources.

would this regulator be suitable for the 405/407 design ? <tongue-in-cheek>


Sat Oct 14, 2017 5:45 am
[zmemw16 – Sat Oct 14, 2017 1:57 am] –
aliexpress – only available in lots of 100, pricing £5.85 to £7.06 from 5 sources.

would this regulator be suitable for the 405/407 design ? <tongue-in-cheek>


that’s what i’m currently using for my 405 design :). for the exact reasons i already posted here :).
For my saber boards i also switched to that one, seemed pretty much ideal for these kind of boards :). And hence i quickly made an adaptor so i could upgrade the various board i have with an AMS1117 to something proper (that AMS is way too popular :p).

Sat Oct 14, 2017 5:54 am
sorry i tend to only read the unread posts of threads.

Sat Oct 14, 2017 5:55 am
[zmemw16 – Sat Oct 14, 2017 5:54 am] –
sorry i tend to only read the unread posts of threads.

lol XD
no problem, i also don’t always read everything or remember everything (even in my own threads :oops: ) :).
but it’s indeed a nice regulator, and i’ve indeed got 100 of them laying around from aliexpress :).

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