very small STM32F405 board

Simple Pito’s 9193 cooler:
Take a piece of wire, ie. 0.4-0.6mm dia, make a small coil from it, say 4-5windings 2mm dia, solder the short leads to pins 1 and 3 (Vin, En) such the coil touches the top of the package. Apply a small dot of glue or (none conducting) thermal paste beneath the coil such it gets better thermal contact to the package. It will cool down the chip via pins 1 and 3 as well as via the top of the package. Not to scale:

9193 cooler.JPG

9193 cooler.JPG (14.8 KiB) Viewed 750 times

In addition to these numeric calculations, I do wonder if anybody has done thermal imaging of F103 and F407 boards to determine if this is a real problem.

Not having the infra thermometer handy, I loaded BPill’s 3.3V rail with 33ohm (5V from USB as the input), so the Iout was maybe 120mA, the temperature of RT’s package (the finger method) was below 50degC (you can keep touching with your finger till about 50degC with a standard human).

With 2x 33ohm in parallel the Iout aprox 220mA, and you cannot touch the package anymore, crazy hot!

Would be great if somebody could measure the temperatures and verify the tables above.

Btw, the fundamental laws of physics are not easy to bypass as of today, the thermal power dissipated by any linear voltage regulator is simply

P = (Uin – Uout) * (Iout + Ireg), [W, V, A], where Ireg could be neglected with modern regs.

[Pito – Sun Jul 30, 2017 11:43 am] –

…you can keep touching with your finger till about 50degC with a standard human…

That is for a metric calibrated human finger. Those of you in the land of Trumpentweet will have fingers pre-calibrated to 122 F

Yes, degC as degree Celsius.. (0degC – pure water freezes, 100degC pure water boils, at the sea level)

[ahull – Sun Jul 30, 2017 1:15 pm] –

[Pito – Sun Jul 30, 2017 11:43 am] –

…you can keep touching with your finger till about 50degC with a standard human…

That is for a metric calibrated human finger. Those of you in the land of Trumpentweet will have fingers pre-calibrated to 122 F

Those of us have such a thick skin by now that our fingers will probably burn before we notice…

[victor_pv – Sun Jul 30, 2017 1:28 pm] –

[ahull – Sun Jul 30, 2017 1:15 pm] –

[Pito – Sun Jul 30, 2017 11:43 am] –

…you can keep touching with your finger till about 50degC with a standard human…

That is for a metric calibrated human finger. Those of you in the land of Trumpentweet will have fingers pre-calibrated to 122 F

Those of us have such a thick skin by now that our fingers will probably burn before we notice…

.. in which case, a keen sense of smell will be needed to determine if the finger is rare, medium or well done.

For people with thick skin and a limited sense for smell there is an another test – the spit test.
Spit at the voltage regulator, and when
– the water boils and evaporates within 3 seconds – the temp is >= 110degC
– you see dancing balls – the temp is >= 210degC

You also may spit at your finger and when it sizzles when touching the regulator the temp will be >=110degC.
The people with musical ear may distinguish the temperature ranges based on the sizzle’s pitch

Use at your own risk, no warranties of any kind..

This is starting to get funny

I found another small F4 board ( F411 ).
It has also a ESP8266 as WIFI interface.
I wonder if it would be complicated to get the thing running.

Seems to be this board

http://www.intorobot.com/downloads/manu … eet_En.pdf

Shame there is no schematic

[ChrisMicro – Tue Aug 29, 2017 6:10 am] –
I wonder if it would be complicated to get the thing running.

It should not, although without schematics, some pain can be faced …