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

Volker Kuhlmann list57 at top.geek.nz
Tue Jul 9 07:28:51 BST 2019

On Tue 09 Jul 2019 07:53:59 NZST +1200, Daniel Powell wrote:

> In terms of reliability, my soldering is shyte so the intent was
> to pot the lot once it's proven to work.

Sorry, potting a breadboard in that kind of shaking environment I'd stay
clear of. Learn to solder... ;-)))

> In terms of noise I was referring to the voltage drops associated with
> turning on massive fan array's, starting the car, running large light
> pods, or blowing an alternator.

Sounds more like brownouts or blackouts than noise!!
Big caps... in front of the regulators!

> The trimmers will be set under load, then glued such that they can't
> be adjusted (and hopefully don't ever need it again).

Hmm. I just don't trust the vibration... And the precision trimmer would
vibrate internally, no difference with potting. I stay with my
recommendation - replace with fixed resistors.

> However I gather from your comments below your choice of the
> regulators posted is the switching UBEC, which shouldn't release so
> much heat?

All of the switching regulators are pretty much the same and I'd use
those. Less heat, less trouble. It's OK to solder modules onto
prototyping boards, but I'd use 2-sided through hole ones, with rings
only (I hate the stripe ones), the through-holing makes the solder joint
much more resistant to mechanical wear.

The stated switching regulator efficiency is best-case, forget it, it
only applies at a single point - the peak of the efficiency curve.
Regulators running at around a MHz are more efficient than those at
180kHz, even at low loads. Real world, say expect about 50-65%. That's
still much better than the 0% of a 7805.

> protoboard. Given the front face is covered in modules I'm keeping the
> wiring on the back face. The face that has the pads. I place a tinned
> insulated wire, through hole next to the pin I require routing, then
> solder bridge from the wire to the pin. I'll attempt to construct some
> traces on power, ground with wirewrap , however I suspect that I'd
> need a multi layer board to feed all my busy displays and the poor
> placement of the ESP (trying to maximize display while minimising
> footprint). Am I doing the right thing, or am I right royally making a
> dogs breakfast of my cheap ahrse Chinese devices?

No, that's OK practice. Thicker ground wires are good. I use 2-sided
protoboard, cables (or bare single-core wire) for ground, and the signal
ones around that. I have yet to find lacquer insulated 1-core copper
wire that can be soldered easily - they're made to withstand coil
temperatures without losing insulation, no good for soldering. Wire wrap
wire is no good for soldering in the middle of the length, tho easy with
a high quality strip tool.

PCBs are so cheap at jlcpcb.com that I must get a handle on using those,
and kicad. (I'm not interested in proprietory, or online-only, tools.)



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

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