[chbot] Car 12v supply to 5v VCC.

Volker Kuhlmann list57 at top.geek.nz
Sun Jul 7 00:50:52 BST 2019

On Sun 07 Jul 2019 09:04:41 NZST +1200, Daniel Powell wrote:

> Sorry for the intrusion with something bound to be a simplistic
> and rather rudimentary question given my lacklustre knowledge in
> electronics.

Glad you asked, that's what this group is for :-)

> https://www.aliexpress.com/item/32280431843.html , LM2596HVS, XL4005 and  XL7015
> https://www.aliexpress.com/item/32961984080.html , 12V LM7812
> https://www.aliexpress.com/item/32921703886.html

Links are better than pics anyway.

Do you mean electrically noisy? Add a few capacitors to power supply
lines at different points, enclose all the electronics in a metal box
and use common mode chokes on cables coming out/going into the box (like
the toroid on your UBEC).

But are you sure it's that noisy? The ESP should be OK in a dash board.
Just try without first, the electrical noise is much more likely to
cause malfunction than damage. And ESPs are <$5...? Perhaps the I/O to
the microcontroller are your bigger problem, if you have long cables
involved? If you're expecting the noise to have some power in it than
simple port protection circuits might be needed (RC, or diodes, or both,
but that also depends on the signal).

I'd be more worried about car vibrations and breadboard. I don't think
that's gonna stick together for long, with reliable electrical
connections, or altogether... you might have a few loose components in
the bottom of the dash at the end of the drive.

Those aliexpress regulators are all good to use. Given it's
china-cheap(TM), the modules will not live up to their max power
promise, the componentry probably has a higher failure rate (worst case
12V into 3.3V ESP... but it' much more likely to fail open circuit), the
tiny trimmer on the small module is a bit desperate, etc.

You might want to replace the trimmers with fixed resistors, because of
mechanical vibrations.

You don't say what the power consumption of your toys are, but I'm
guessing maybe 0.5A. The 7805 regulators are potentially more reliable,
but at (12-5)V*0.5A=3.5W you'll have meltdown without heat sinks. The
switchmode regulators waste maybe only 1/3 of the power.


Volker Kuhlmann
http://volker.top.geek.nz/	Please do not CC list postings to me.

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