I'm working on an invention that will work in the car. The available power input is the nominal 12-15V battery input. I always believed that car electrical systems can have spike much higher than the nominal voltage, so I bought components that can handle 24V maximum. And then, I read somewhere that car systems can spike with +60V. So... I'm now looking at a simple way to cap that high voltage so it doesn't fry my power components.
Please see the diagrams and validate my assumptions. 1) Nominal 12V when the car is powered off. 2) Car provides maximum voltage my components can handle; 2) Car spikes with 60V.
Does anybody see a problem with my logic here? Thanks very much for your feedback. I have basic electrical knowledge and I'm new to Arduino since last year.
And by my design, if I should get something like a lightning strike and +61V then I would fully expect to lose some hardware here. But I figured it would be good sense to protect for 60V.
I searched for Zener diodes and found a number on Digikey that are in stock, cost < $1, with a Zener voltage of 24V, tolerance 5% and a power rating of 1W. Examples:
6000 Ohms is a problem. Most of the voltage will be dropped across the resistor and the maximum current (at 12V) will be 12/6000 = 2mA.
Generally a voltage regulator provides pretty good over-voltage protection.
And if you use a Zener, the Zener does need to be protected against excess current so usually a current-limiting resistor is used and that means this kind of circuit is normally only used for low current "signals", not for power. Or, you can use a fuse but then every time there's a voltage spike with a duration long-enough to blow the fuse, you have to replace the fuse.
Generally a voltage regulator provides pretty good over-voltage protection.
Oh... well my buck converter (HW-613) does in fact say that it has overvoltage protection... but its rated max as well as the rated max on the low voltage shut-off thing, are both 24V.
I agree. In a 1985 model car a single board computer was running perfectly for 10 years powered by a 7805. Some caps on the input and prescribed caps on the output only.
I might be wrong but modern cars ought to be less noisy for all the advanced electronics to run.
Zener diodes are generally speaking only for low current stuff.
Look at TVS diodes for power protection.
An 18volt TVS (super-zener) would be ok to protect a 12volt car supply.
Leo..
The thing to look for is "standoff voltage". That has to match max supply voltage.
16volt standoff means that the diode does not conduct yet at 16volt. At 18volt it just starts conducting, and 26volt (200Amp) could blow it if that would last long.
Leo..
then I would fully expect to lose some hardware here. But I figured it would be good sense to protect for 60V.
Most of the voltage will be dropped across the resistor and the maximum current (at 12V) will be 12/6000 = 2mA.