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.
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..
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.
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.
