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

Daniel Powell danielvieway at hotmail.com
Mon Jul 8 20:53:59 BST 2019

Volker, thankyou for the reply. 

In terms of reliability, my soldering is shyte so the intent was to pot the lot once it's proven to work. Given it's in an offroad race car (extreme vibration and impacts) and a rally car (constant vibration, hopefully without impacts) I don't think I'll get away without potting it somehow. However this is more of a project for firing neurons than construction of a viable commercial product. If it proves reliable then I'll get a board printed for it and perhaps remove the intelligence from the displays, run an ESP32 chip rather than a prototype module and integrate it into the board. As it is, it's a tight conglomeration of modules that doesn't optimize traces.. at all!

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. 

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

Given the 7805 will need a more substantive heatsync I'll invert it and run a plate alongside the outside of the casing. 

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

It's certainly less than .5A draw in that it runs from a 2.0 spec PC USB connection. I should have run my inline USB power meter on it..... whoops. Once I complete the protoboard wiring I'll do so. 

Which you may also be able to assist me with. 😊
In terms of protoboard I've through hole soldered the modules on a single sided 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? 

Thank you so much again for the pointers. 


-----Original Message-----
From: Chchrobotics <chchrobotics-bounces at lists.ourshack.com> On Behalf Of Volker Kuhlmann
Sent: Sunday, 7 July 2019 11:51 AM
To: Christchurch Robotics <chchrobotics at lists.ourshack.com>
Subject: Re: [chbot] Car 12v supply to 5v VCC.

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 :-)

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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
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