Protecting an Output

For a series capacitive load, is it necessary to protect a pin from voltage spikes?

Is the circuit graciously provided by Grumpy_MIke (http://www.thebox.myzen.co.uk/Tutorial/Protection.html) appropriate?

Is a series resistor enough protection?

An output pin? Usually one is worried about current surges as a discharged cap looks like a short. Series resistor for that, for a MOSFET gate for instance.

That web page was about protecting inputs.

So this sort of spike...

http://arduino.cc/forum/index.php/topic,64256.0.html http://arduino.cc/forum/index.php/topic,64256.msg471812.html#msg471812 http://arduino.cc/forum/index.php/topic,64256.msg471830.html#msg471830

...is not detrimental to ATmega8U2? (to the output pin)

Those threads were confused about what they were measuring and why.

The spikes were on the reset which is an input. They are present because of a logic level signal being AC coupled. They were fixed by having a clamping diode to the +ve rail.

Post the schematic of what you are worried about.

No need for a schematic... pin, resistor, piezoelectric buzzer (with a relatively high capacitance), ground.

With your posts and @CrossRoads' post I now realize: 1. I'm being paranoid; 2. I'm being foolish.

  1. I'm being paranoid; 2. I'm being foolish.

No always a bad thing. Better to ask if you don't know. :)

Thank you (and @CrossRoads) for the help! Off to play with Tiny Core 2...

  1. I'm being paranoid;

Not always a bad thing.

Those wise words remind me that later this summer I'll be in a part of the country that sports rattlesnakes. Gives me chills thinking about it.

Yee ha partner! Get those cowboy boots out.

I don't get along very well with cowboy boots. I wonder if New Balance makes a good snake resistant shoe... :astonished:

Kevlar gaiters...

But you're from Dallas? You can find great boots there. Over in the stockyards even. I had a vendor in Brenham, TX. There was a great boot store in the same town, or maybe 1 town south, in that vicinity. We went there a couple of times, and I got a pair of boots both times. When I wore the heels or soles out, I'd send them to this same vendor and the contracts manager would take them to a great bootery she knew of to have them redone. Too bad I changed jobs and don't work with them anymore.

May I recommend a mine-clearing robot? Flail model, preferentially for a path 6' wide with a built-in nuclear reactor for extra range and the possibility of plugging in a portable AC unit? :)

Constantin: May I recommend a mine-clearing robot? Flail model, preferentially for a path 6' wide with a built-in nuclear reactor for extra range and the possibility of plugging in a portable AC unit? :)

You forgot the beer cooler in the specs for the unit.

Becks loescht kennerdurst. :)

later this summer I'll be in a part of the country that sports rattlesnakes.

I went to Nevada in October and it was sweltering hot. Went walking in Red Rock Canyon and the man in the visitor's center said it was too cold for rattle snakes that day.

In the summer in the Southwest (when it is hot), you pretty much don’t have to worry about rattlesnakes, unless you venture into shaded rocky areas… They like to hang out in the cooler shaded crevices. Since it is warm, if you encounter one in such a scenario, you will most likely get bit… That rock looks like a good place to rest (snake thought so too, thats why he is biting your ankle… Its his way of telling you that the rock is his…)

The odds of encountering a rattlesnake actually improve when it is cold, but in cold situations you will have a lower chance of getting bit… An uncle one awoke to a bull snake in his bed roll while out camping during hunting season (late fall)… After we stopped laughing we just explained that the snake just wanted to get warm as well…

I have spent a lot of time traipsing around the back country of the southwest. Only two things are needed (in order of importance); 1. Good listening skills (a rattlesnake will warn you well before they strike) and 2. A good walking stick. The walking stick will let one poke dark crevices near rest stops to ensure the area is not previously occupied…

CrossRoads: But you're from Dallas? You can find great boots there. Over in the stockyards even.

Oh, I know. It isn't a question of boot quality but an issue of odd feet. Some sneakers (and a single pair of work boots) are the only thing I have found that fit my feet.

We went there a couple of times, and I got a pair of boots both times. When I wore the heels or soles out, I'd send them to this same vendor and the contracts manager would take them to a great bootery she knew of to have them redone. Too bad I changed jobs and don't work with them anymore.

I have a similar story involving dress shoes that I loved. A house flood ruined the uppers after the manufacturer stopped making them. Man I miss those shoes. Here it is a few years later and I still have not found replacements.

Grumpy_Mike:

later this summer I'll be in a part of the country that sports rattlesnakes.

I went to Nevada in October and it was sweltering hot. Went walking in Red Rock Canyon and the man in the visitor's center said it was too cold for rattle snakes that day.

Oh, you Brits. Afraid of a little (sweltering) heat. ;)

wanderson: In the summer in the Southwest (when it is hot), you pretty much don't have to worry about rattlesnakes, unless you venture into shaded rocky areas... They like to hang out in the cooler shaded crevices.

A perfect description of where I was this afternoon. :astonished:

Only two things are needed (in order of importance); 1. Good listening skills (a rattlesnake will warn you well before they strike)

That has always been my experience with one addendum. For me, it has occasionally been difficult to tell exactly where the snake is. I've even walk past the snake before it rattled. I've found it wise to stop, quickly determine the snake's location, and then take action. Lest ye may step on the nasty critter.

  1. A good walking stick.

A 6-footish walking stick with short Y legs is handy. The Y end can be used to push the snake away.

The walking stick will let one poke dark crevices near rest stops to ensure the area is not previously occupied...

Oh yeah! I've been poking at all dark areas!