I fried my Arduino Mini...

[stj]

Re: I fried my Arduino Mini...

put a uf5408 in parallel with the first zener.

to soak up any negative spikes cause by inductive shit turning on and off in the car.
stuff like blower motors and the starter.

[eccerr0r]

Re: I fried my Arduino Mini...

Well, the worry is if someone decides to use a stick through the window and press the buttons from the outside, gaining entrance to your car because the power windows were active...

Unless you write the code that you may only close the window when key is not in the ignition...

[Dannyx]

Re: I fried my Arduino Mini...

It would be a bit tricky to do the stick thing anyway because the rockers are on the dash under the stereo (photo to get an idea of the interior of this car). There's two extra lines of defense against this: power only goes to the rockers when the key is in the ACC position naturally, so those optoisolators wouldn't activate anyway and second the code is written to detect the ignition and only then allow UP/DOWN movement.

[Dannyx]

Re: I fried my Arduino Mini...

put a uf5408 in parallel with the first zener.

to soak up any negative spikes cause by inductive shit turning on and off in the car.
stuff like blower motors and the starter.

Yes, good idea. Would any schotkky (spelled that wrong for sure) do ? Any reason why you went straight to that particular one and didn't use the generic "A schotkky" ? (spelled it wrong again)

EDIT: I wasn't that far off apparently: Schottky

[stj]

Re: I fried my Arduino Mini...

that's not a schottky, it's just very fast.

btw, the way to get into a car.
method 1: use a "jim" down between the glass and seal to hook the rods connecting the lock to the internal handle.

method 2: use a mini airbag to bend the upper corner of the door open enough to insert a rod, then again - hook the internal handle.


these are how professionals do it, knowing this you can create shielding to block them off.

[Dannyx]

Re: I fried my Arduino Mini...

Car's been broken into several times now - nothing left to steal LOL It's even easier than what you "suggested" with this particular line of cars because they had a HUGE problem with their lock system and is very easy to break into. I'm surprised they haven't been recalled. Simply inserting a sturdy tool like a screwdriver or a piece of metal into the keyhole and giving it a sharp jerk up/down pulls out the lock cylinder and the door opens just like that. No alarm means hakuna matata...you're in and you're out....Stereo's been stolen once but that's about it, since I never keep valuables in the car anyway, it would be stupid to do so. It's not so much about anything getting stolen as it is about the damage done to the doors themselves which then need bogging/straightening/painting, etc .
I've now removed both locks and covered the holes with steel caps bolted from the inside of the door to eliminate this issue and make it at least a little bit more difficult to crack...sure, if someone's determined to get in it CAN be done, even if by smashing a window or other "extreme" methods, but this hopefully slows them down long enough that someone notices or they give up...it's the fate of cars that don't reside in a garage I'm afraid - they're exposed to everything...anyway, I digress like I always do...

[Curious.George]

Re: I fried my Arduino Mini...

I have had these types of mishaps happen to me before until I figured what was causing the problem it was a good thing that these parts were not very expensive

It has happened on a project that I am working on now

https://www.badcaps.net/forum/showthread.php?t=70594

I was trying to use a mosfet switcher was to small in amperage so I fry a few of them

In the late 70's, a buddy was working on a 2000V, 2000W power supply. The FETs used in the switcher were $50/each (I think he may have used 4).

The running joke was that the devices were fused to protect from gross faults. But, in practice, that the FETs were used to protect the fuses from blowing!

[Dannyx]

Re: I fried my Arduino Mini...

Back on topic, I did some experimenting and here's how I got it laid out at the moment.

Initially, I started off with R1 at 100 ohms, but that was a bit too high and the voltage at VCC pin was only around 3.8v. I then dropped it to a 82 ohm resistor (which is only because that was the closest value I had in my drawer of resistors). The buck already outputs 5v, so the zener's there for protection only since it doesn't regulate or conduct anything. I got the idea for this setup recently from an "AUX" winding of a Toshiba PSU (some of you guys probably know about that too) where the zener did not actually regulate, but simply "guard" against spikes.

At first I miscalculated: I thought 5v from the buck going across the 100ohm resistor would give me a maximum possible current of 0.05 amps (50 miliamps) to work with. V/R = I >>> 5/100 = 0.05 is what I thought, which I thought was plenty of current to power the board without "sagging", but the voltage dropped to 3.8v on that rail like I said. I then dropped to 82 ohms and it works. The rail is now around 4.1v, which is still a bit too low, but doable. C1 and C2 are 0.1 uf ceramic caps I just bothced on there...not sure if it's a good/bad/useless idea...

[stj]

Re: I fried my Arduino Mini...

c1 seems useless to me.
c2 would be better with some guts - maybe 10uf tantalum. the arduino already has ceramic decoupling.

[Dannyx]

Re: I fried my Arduino Mini...

Didn't have tantalums of such a value on hand, but I did have some 220 nF ones, three of them to be exact, so I stuck those in the breadboard one after another for now
Idiot question: are tantalums polarized ? I think they are very much so.... I see no markings on these ones, but I recall a while back I sent my buddy to pick some up and those HAD a plus sign on them, so I think these are not tantalums, but poly films....is this true ? I don't know my basics apparently

[stj]

Re: I fried my Arduino Mini...

yes they are polarised - and burst into flames if you get them backwards!!
stripe = positive end.

the thing in your photo is a multi-layer ceramic cap

[eccerr0r]

Re: I fried my Arduino Mini...

Why do you want a zener regulating the buck SMPS, would it not already be regulated? That is unless the SMPS is far away, in which IR drop would then be a problem too...

[Dannyx]

Re: I fried my Arduino Mini...

It's not regulating. It ensures it doesn't go over....I know, it wouldn't happen, but just in case...just a theory

[stj]

Re: I fried my Arduino Mini...

the word your looking for is "crowbar circuit"

[Dannyx]

Re: I fried my Arduino Mini...

Yes, I'm familiar with that, now that you mention it. I calculated that the setup with the 5v zener and the 82 ohm resistor could take up to 20v "overhead", which shouldn't/can't possibly happen, but what the hey

1. 20v-5v (zener rating) = 15v dropped
2. 15v/82ohms = 0.18a approximately
3. 0.18a x 5v (zener rating ) = 0.9/1w for the zener with no load present
4. 0.18 x 15 = 2.7w for the resistor...would get hot, but it shouldn't come to this anyway.

Hope I got it right

[eccerr0r]

Re: I fried my Arduino Mini...

You should be protecting the SMPS not the downstream circuit. The trash power is on that side of the circuit.

[Dannyx]

Re: I fried my Arduino Mini...

I was thinking of that...what are the chances of catastrophic failure on a small buck module like that and what would happen to the output rail ? Would it short to GND or VCC ?
I shall repeat the setup with the "primary" side too as we've discussed: diode across the terminals and possibly a zener tuned to the maximum voltage the buck's designed to handle safely.

[eccerr0r]

Re: I fried my Arduino Mini...

What are the chances of catastrophic failure is related to how crappy of a converter you bought?

[Dannyx]

Re: I fried my Arduino Mini...

I don't expect they're anything too high quality at like 3-4 bucks for 3 pieces...what'u gonna do

[stj]

Re: I fried my Arduino Mini...

one of them is very good, i use them.
https://www.ebay.co.uk/itm/3PCS-Mini...-/322270626721

there is an older design with a huge TO220 regulator that is not so great.