Bluepill: max. voltage on 5V pin?

In my recent project i have a 12V power supply. As I am lazy and I don’t want to spend an extra DC/DC converter,
can I wire the 12V directly to the 5V pin, or will the 3.3V regulator send smoke signals in this case?

Regards
stancecoke

stancecoke wrote:In my recent project i have a 12V power supply. As I am lazy and I don’t want to spend an extra DC/DC converter,
can I wire the 12V directly to the 5V pin, or will the 3.3V regulator send smoke signals in this case?

Regards
stancecoke

@Ray makes a good point. One other thing to consider is that there are lots of variants of these boards, so any advice would be specific to a particular variant. Also, there is some doubt if the regulators on some of the boards are actually genuine.

Some boards use an AMS1117 3v3 regulator -> http://www.advanced-monolithic.com/pdf/ds1117.pdf (often marked A117, 1117, or something similar). They are in theory able to tolerate 15V on their input, however, this supposes that a) your board uses this particular regulator, b) the regulator you have is a genuine part, and c) your additional load on the regulator will be within the spec. of that regulator when run at 12V (for the answer to that, you need to consult the datasheet). If in any doubt, add your own regulator, they are jelly bean parts and only cost a few cents.

So in summary, try it and see, but the risk (while low) is entirely yours, or add a separate regulator. If you do pop the regulator, let us know, membership of the magic smoke club is free and new members are always welcome.

http://www.stm32duino.com/viewtopic.php?t=22
http://www.stm32duino.com/viewtopic.php?t=1266

Thank you for your suggestions. On my Bluepill, the LDO is labeled with “DE=A1D”. Google says it is a http://www.richtek.com/assets/product_f … 193-16.pdf

Absolute Maximum Rating for Supply Input Voltage = 6V So I will have to spend separate regulator or DC/DC converter…

Regards
stancecoke

stancecoke wrote:Thank you for your suggestions. On my Bluepill, the LDO is labeled with “DE=A1D”. Google says it is a http://www.richtek.com/assets/product_f … 193-16.pdf

Absolute Maximum Rating for Supply Input Voltage = 6V So I will have to spend separate regulator or DC/DC converter…

Regards
stancecoke

Spending $0.50ea qty 50 is what I did for the ESP8266 where it is extremely critical to have a low-Z power supply output impedance.

The STM32F103 IMO does not require such low-Z, but it certainly will not hurt anything!

Ray

I will use a LM7805, as I have several ready to hand…

Regards
stancecoke

Hijacking this thread, as my question is very similar.
I recently got a batch of blue pills, and I was trying to follow the suggestions on this topic to find out what the voltage regulator is, and what’s the max voltage.
However I’m not able to properly decode the model…
It seems something like “S2Q6”, or “S2QG”, but looking up on google these codes doesn’t seem to show anything relevant.
Has anyone ever encountered this kind of voltage regulator?

Cheers,
Marco

LM7805 comes in many packages, but all capable of only dissipating so much heat.

roughly dropping from 12-14v to 5v, means 7 to 9 * current drawn (mA) mW
make sure you have a sufficiently large heat sink attached.

stephen

Discussed a few times here already – that voltage regulator’s package (in the BPill) has got a high thermal resistance (bad cooling), so it will overheat easily even at 5V input.

well you could get a Baite MM clone instead of BP
https://www.aliexpress.com/store/produc … 46722.html
https://www.ebay.com/sch/i.html?_nkw=st … i&_sacat=0

that uses AMS1117 with a max 15V given in the spec and accordingly it can deliver up to 1A downstream
http://www.advanced-monolithic.com/pdf/ds1117.pdf

but i’d think sinking 12v to 5v, there’d be a lot of waste heat, it would run hot as well given the high voltage drop and you’d still need to find a way to do some heat sink

One of my Baite clones emitted magic smoke when its owner inadvertently connected it directly to a 12+V automotive feed. It’s now eking out a lonely existence at a landfill somewhere so I’m unable to check the regulator markings.

uh oh, thanks for posting that, it’s probably pretty good warning
my guess is to feed off 12v, it would probably be better, safer, more efficient to feed off a low cost step down buck converter
https://en.wikipedia.org/wiki/Buck_converter
https://www.ebay.com/sch/i.html?_nkw=bu … r&_sacat=0
pretty much an overkill as a buck converter typically supply much higher currents downstream, but when loads is light it could consume much less as well and possibly run cool, the capacitors could be smaller too

[BennehBoy – Sun Dec 17, 2017 11:30 am] –
One of my Baite clones emitted magic smoke when its owner inadvertently connected it directly to a 12+V automotive feed. It’s now eking out a lonely existence at a landfill somewhere so I’m unable to check the regulator markings.

Spew Alert to others … do not drink coffee while reading the above …

Ray

[BennehBoy – Sun Dec 17, 2017 11:30 am] –
One of my Baite clones emitted magic smoke when its owner inadvertently connected it directly to a 12+V automotive feed. It’s now eking out a lonely existence at a landfill somewhere so I’m unable to check the regulator markings.

best post of 2017 ?
should there be a competition ? new thread?
srp