Maple mini and RC lipo’s – how to taste the black magic smoke again

madias
Tue May 17, 2016 11:52 am
Just a little warning:
While playing around with 2s RC lipos (8.4V, up to 40-80A discharge power!!!) I burnt out a maple mini (not the BAITE version) very quickly (maybe only the voltage regulator, I’ll check this later). Even with the BAITE ones (they have the “bigger” AMS1117 clone voltage regulator) I wouldn’t connect them directly to such powerful lipos: I burnt those AMS clones on other devices – they are really bad made and after they are dead, they tend to give the whole input voltage to the output.
This happend without any particular load on the mini!
As a silly and cheap workaround I use a separate LM7805 (with heatsink) to reduce the power and connected it to the “Vin” of the maple.

racemaniac
Tue May 17, 2016 12:16 pm
madias wrote:Just a little warning:
While playing around with 2s RC lipos (8.4V, up to 40-80A discharge power!!!) I burnt out a maple mini (not the BAITE version) very quickly (maybe only the voltage regulator, I’ll check this later). Even with the BAITE ones (they have the “bigger” AMS1117 clone voltage regulator) I wouldn’t connect them directly to such powerful lipos: I burnt those AMS clones on other devices – they are really bad made and after they are dead, they tend to give the whole input voltage to the output.
This happend without any particular load on the mini!
As a silly and cheap workaround I use a separate LM7805 (with heatsink) to reduce the power and connected it to the “Vin” of the maple.

Pito
Tue May 17, 2016 12:20 pm
What could be the power loss and the temperature (sot-223)?
U = 8.4V I=50mA
P = 8.4*0.05 = 0.42W
T = 25 + 0.42W*90C/W = 25 + 37.8 = 62.8C
63degC cannot damage the 1117 voltage regulator, I guess..

WereCatf
Tue May 17, 2016 12:39 pm
Maybe Madias shorted something or connected the batteries on wrong pins, or wrong polarity, or something? No matter how much current the batteries can put out the device shouldn’t care since it’ll only draw what it actually uses?

zmemw16
Tue May 17, 2016 2:10 pm
sorry people, ams1117 pdf says mtbfis 4100hrs odd, does not mean a life of that, failure usually at power off / on.
failure at the first on-to-off is normally found out at the second the off-to-on. :D

5v into a LM7805 does not give out 5v, almost certainly below V-usb, what then happens is higher level wins!

stephen


ahull
Tue May 17, 2016 2:57 pm
zmemw16 wrote:… ams1117 pdf says mtbfis 4100hrs odd…

zmemw16
Tue May 17, 2016 3:16 pm
oops, eyesight failure, somehow F. 4 became F 4.
absolutely no idea how the brain cell did that.

IEC/EN General Safety. Report: SPCLVD 1407030-1. IEC/EN-60950-1, 2nd Edition. MTBF (25°C). MIL-HDBK-217F. 4185 x 10³ hours. (70°C). MIL-HDBT-217F
.


WereCatf
Tue May 17, 2016 3:23 pm
zmemw16 wrote:oops, eyesight failure, somehow F. 4 became F 4.

Pito
Tue May 17, 2016 6:01 pm
Pito wrote:What could be the power loss and the temperature (sot-223)?
U = 8.4V I=50mA
P = 8.4*0.05 = 0.42W
T = 25 + 0.42W*90C/W = 25 + 37.8 = 62.8C
63degC cannot damage the 1117 voltage regulator, I guess..

zmemw16
Tue May 17, 2016 8:21 pm
so 40yrs then :D

once upon a time i modified my motorbike with a solid block full bridge rectifier, it handled the 6v to 12v inverter for the 55W halogen full beam headlight. took about 8 secs to ramp up the extra load, not good at 60mph at night.
now i’m thinking i’m puzzled as to why i needed a bridge rectifier ?
i’d also changed it from a single carb to a twin carb head, so said rectifier got stuck in an empty space with a rag to stop the rattle.
70 miles down the motorway, in the outside lane at 70mph, i always had the headlight on, i had a 12″ square smoke tail right under the petrol tank.
i’ve never known how i got to the emergency lane, with the luggage, seat with its two rounded over hex head bolts, wiring harness and petrol tank all off in about 30-50 seconds. needed a new pair of gloves.
now i tend to overly heat sink things.

i’ve only ever done this once.
take one 6v electrolytic cap, fed it full wave rectified 6v ac, eyes got it, blind 5 flights of stairs yelling gangway from my newly rented room to the nearest water in the kitchen.

stephen


ahull
Tue May 17, 2016 10:16 pm
zmemw16 wrote:
i’ve only ever done this once.
take one 6v electrolytic cap, fed it full wave rectified 6v ac, eyes got it, blind 5 flights of stairs yelling gangway from my newly rented room to the nearest water in the kitchen.
stephen

RogerClark
Wed May 18, 2016 1:43 am
The only reasons I can think for this to happen, is that the LiPo’s are incredibly low impedance, and can overload the regulator with current when it charges the caps on the 3.3V side.

But this sounds really unlikely, unless very thick wire was used to connect to the regulator.

Perhaps the regulator is a cloned product and has reduced operating limits?


madias
Wed May 18, 2016 6:00 am
RogerClark wrote:
Perhaps the regulator is a cloned product and has reduced operating limits?

zoomx
Wed May 18, 2016 6:28 am
You’re right. I found this post
Beware of fakes. I have a bag full of AMS1117-5 (SOT223) here that fail in unpleasant ways (pass input direct to output) when you exceed about 10v input, at any current draw. As long as you don’t exceed about 10v input they are ok,

ahull
Wed May 18, 2016 12:06 pm
zoomx wrote:You’re right. I found this post
Beware of fakes. I have a bag full of AMS1117-5 (SOT223) here that fail in unpleasant ways (pass input direct to output) when you exceed about 10v input, at any current draw. As long as you don’t exceed about 10v input they are ok,

mrburnette
Wed May 18, 2016 12:19 pm
Aliexpress and DX have lots of counterfeit components.

OK, folks … the above is just a complete distortion of fact. I’m going to defend Aliexpress since it is my primary off-shore store and I have no experience with DX; but Alliexpress is a wrapper service and not the seller. I seriously doubt there is much oversight from mother Ali, but I do know that I have had one order canceled by Aliexpress when the vendor appeared to oversell their inventory. Aliexpress put a 10-day hold on all orders and required the vendor to “prove” supply capability. No charges were ever placed on my credit card.

IMO:
If you buy from off-shore Asian sources, you need to do your own quality testing. QA for items that seemingly are near free when free shipping is considered are almost assuredly not fully tested – if tested at all.

So, if you buy a PSU or even those ugly prototype power units – test them! Honestly, PGM (piss-gripe-moan) will only go so far toward making you feel better… the best defense is a great offense. TEST FIRST.

Ray


ahull
Wed May 18, 2016 1:01 pm
+1 to Ray’s post. There is a reason why real companies do real QA. It costs money, but it saves you so much heartache. Having spent time designing diagnostics and more recently assisting with software QA, I know how important it is. I have no quibbles about using the cheapest of the cheap for hobby stuff, but if my reputation and my business depended on it, then known suppliers and rigorous QA are the order of the day. If the competition want to sell their product cheaper, without QA, hell mend them. :lol:

WereCatf
Wed May 18, 2016 1:03 pm
mrburnette wrote:and I have no experience with DX; but Alliexpress is a wrapper service and not the seller.

Pito
Wed May 18, 2016 1:56 pm
All today’s voltage regulators have got at least a) overcurrent protection, b) thermal overload protection..
The AMS1117 series of adjustable and fixed regulators are easy to
use and are protected against short circuit and thermal overloads.
Thermal protection circuitry will shut-down the regulator should
the junction temperature exceed 165°C at the sense point.

Unless the regulator is a fake, or a defect unit, the only way you can destroy it with a “fizz”, is a) wrong polarity of the Vin, b) pins mismatch, c) high input voltage Vin, d) maybe a high inductive load (generating highvoltage peaks).
A high capacitive load (ie 1F blocking capacitor at Vout) should not have destroyed the regulator as the overcurrent protection does not allow that.
A high temperature of the package, ie. 140°C will decrease its life, however..

madias
Wed May 18, 2016 2:08 pm
Ok folks,
it has a reason why I put this thread under “maple mini”:
As we all know there are two different kinds of the maple mini clone out there:
The BAITE one (with the large AMS(?)1117))
the “other one” (with a two small (smd transitor like) voltage regulators) – It seems it’s not really available at the moment.

The “other one” was destroyed while connecting it directly to a 2s lipo (40C).
So I (and other ones here) researched a little bit and found out, that many chinese clone voltage (especially AMS1117) regulators may make big problems with higher voltage / ampere.

So the big question is, if also the BAITE ones are involved by this problem so we should add a warning to the Wiki.


mrburnette
Wed May 18, 2016 2:21 pm
madias wrote:
<…>
So the big question is, if also the BAITE ones are involved by this problem so we should add a warning to the Wiki.

zoomx
Wed May 18, 2016 3:45 pm
I bought from DX (was DealeXtreme) some years ago. It is like a big seller on Aliexpress, they sell the same things. The difference is that you can have all packets with tracking and tracking was free when the order was over about 5$, today is more.
I never reviewed any item but sometimes you can understand something about the quality.
DX has also a UK, USA and AU shops with much less items, never bought from there.

I agree with ray but I am not a professional, I buy items for fun. Very few devices are working on italian volcanoes doing simple tasks like moving a mirror for an instrument (an FTIR spectrometer).


Slammer
Wed May 18, 2016 9:12 pm
Beware with AMS1117, it is a linear regulator and you have first of all to respect the power limit.
The typical thermal resistance of SOT-223 package soldered on PCB is about 80-90 C/W.
The power limit is calculated:

Tmax = Tambient + W * 90

Tmax = 125 by datasheet, and Tambient=40, then:

Wmax =(125-40)/90 = 0.95W

It is very easy to calculate the maximum current of device given the input voltage. Some examples:

Vin=8.5V, Vout=3.3 => Imax = 0.95 / (8.5-3.3) = 182 mA, much lower than rated current of device.
Vin=8.5V, Vout=5 => Imax = 0.95 / (8.5-5) = 270 mA
Vin=12V, Vout=5 => Imax = 0.95 / (12-7) = 190 mA
Vin=12V, Vout=3.3 => Imax = 0.95 /(12-3.3) = 109 mA

Normally, AMS1117 has internally thermal protection that switches off the output if the temperature is beyond limits, but you can not depend on this, specially with questionable quality parts.
All cheap breadboard power supplies use AMS1117 in SOT-223 package. The power limit of this device is very low, try to feed it with an external regulator with as low voltage as possible, to reduce the heating dissipation ( Vin must be greater than Vout+1 )


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