How does my automotive 12v to 5v circuit look?

Still a beginner at all this but I’m trying. Using an arduino nano for what I’m trying to do is still overkill, so I’ve been trying to take a stab at using an ATTINY85. Here’s the 12v-5v circuit I’ve been able to come up with over many hours of searching and trying my best to learn. If anyone can tell me if what I have is solid, or if I should change anything please feel free. If you have a good method that has worked for you I’d love to hear it. I’ve also linked all the datasheets below.

My circuit will be used in a vehicle to control aftermarket lighting (I have another circuit (not shown) using ATTINY to control that) so this 5v circuit needs to be capable to handle all of the horrible nonsense automotive 12v appears to have (transients, load dumps, noisy), hopefully the ESD/TVS I’ve selected can handle it, also almost all the components selected are AEC qualified.

Before anyone says just use a USB adapter… I’m not trying to cobble things together with multiple boards, hence why I’m working on my own 5v circuit to include on my custom pcb.

Components:
D1: SMA6J5.0CA-TR
IC1: ZLDO1117QK50TC
C1: C1210X106M3RACAUTO
C2: TPSC107K010R0150
– optional, for testing –
R1: ERJ-U06J151V (150Ohm)
LED1: 150080GS75000 (150Ohm)

The absolute maximum of 18 V may be a little close for an automotive application.

Don’t forget to provide a generous sized heatsink.

SMA6J5.0CA-TR
A TVS diode with a stand-off voltage of 5volt on the 12volt car supply can't be good.
Better use an 18volt stand-off unidirectional TVS there. And a (fast) fuse.

Maybe easier to use a (switch-mode) cigarette lighter style USB charger, made for this sort of thing.
Leo..

I use a dc to dc buck converter, cheap from aliexpress an that works good on my pro mini straight into the vcc pin....

I'll probably get killed now by the experts here..... but is does work (for now)

I use a dc to dc buck converter

It is a good idea to have transient and polarity reversal protection in front of the converter, as transients of > 125V are often observed in automotive power systems. An 18V TVS diode with a fuse is standard and very cheap.

Hi

All my circuits are automotive and I use the attached circuit on all of them and have never had a problem with noisy electrics or voltage spikes.

Had this circuit working a speedometer on a car from the 70s with lots of hostile spikes without a glitch.

jremington:
It is a good idea to have transient and polarity reversal protection in front of the converter, as transients of > 125V are often observed in automotive power systems. An 18V TVS diode with a fuse is standard and very cheap.

How does the car battery handle that? Can't be good good... I thought the alternator has a regulator providing a stable voltage thees days. I have a ardyino monitoring voltage every half second. when engine is running itaxes out at 14.4volts.

Btw not intending to hijack this topic so if OP want me to ask three questions in another topic I'm good with that.

How does the car battery handle that?

Just fine. It does a little chemistry with the spikes.

Detailed information on voltage spikes in automotive circuits and protection from them here.