#avr Logs

Jun 24 2021

12:02 AM Phantom: the problem I actually have is to get proper parts, that won't fail when the alternator dump it's power and I get spike well past 24V
12:16 AM vmt: well like rue said, you need fuck all power, user a zener shunt
12:16 AM aighearach: Phantom: I would just use a 555 with a good regulator and a current-limiting resistor. You could also use an isolated buck converter though that adds a lot of expense (a few dollars)
12:16 AM aighearach: a zener is too slow, probably
12:16 AM Phantom: depend on the setup
12:17 AM aighearach: assuming you limit the current so you're not wasting excess power
12:17 AM Phantom: VCC -> R -> C -> Z -> LDO
12:17 AM vmt: hmmpf, it may, or may not be
12:20 AM aighearach: If it is a typical robust LDO I'd do VCC -> LDO -> R -> Z -> C
12:21 AM Phantom: https://tinyurl.com/ydrlae52
12:23 AM Phantom: actually.... this may work for once...
12:23 AM Phantom: https://tinyurl.com/yzeg7e5z <=== the diy ldo
12:25 AM aighearach: That's probably fine, it's hard to get the voltage exact but that won't matter
12:25 AM Phantom: yeah, will have to do some fidling, but will ends up with a real ldo
12:25 AM Phantom: good enought for sim
12:26 AM aighearach: The nice thing about an off the shelf LDO is that it dissipates heat well, that's also why I use a 5V zener after it to catch transients instead of a 25V before it
12:27 AM aighearach: A jump start from a tow truck can hit you with low impedance 26-28V
12:27 AM aighearach: So I assume 32V max for automotive
12:31 AM Phantom: I saw spikes in normal use of 24V, and some 78l05 fried when the ground got loose
12:31 AM Phantom: the 78l05 is 35V rated afaik
12:31 AM Phantom: and after it won't catch the input spikes
12:31 AM Phantom: which damage the ldo
12:58 AM aighearach: 78l05 might only be 20V rated?
12:59 AM Phantom: the one I checked was 35V
12:59 AM aighearach: Still, absolute max voltage is often just talking about when the mosfets died from over-voltage, it doesn't imply that it can withstand near that much without current limiting
02:51 AM specing_ is now known as specing
08:26 AM rue_mohr: well
08:26 AM rue_mohr: a zener shunt is ldo
08:27 AM rue_mohr: or
08:27 AM rue_mohr: take that circuit I did and put a ...
02:51 PM specing_ is now known as specing
05:35 PM -!- #avr mode set to +o by cadmium.libera.chat
05:45 PM -!- #avr mode set to +o by cadmium.libera.chat