Best way to ensure signal does not exceed 5v?

Sep 02, 2011 53 Replies

Right. Zener diodes (as opposed to avalanche diodes - ~6V and up) are really crappy. Avoid them whenever possible.

In this case, the 5V rail is handy, so unless there are some really strange mitigating factors, adding any sort of reference diode is dumb.

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An

You're getting as good as your pal, AlwaysWrong, here John. It was a brain fart, sure, but not a typo. Your excuses are instructive, though.

I guess now we all know why you don't even call yourself an engineer. You want to spend over $6 on a half-cent solution. ...and then whine at the half-cent solution because it's "crap". Very telling.

You're the king of dumb, here, John.

It's an important improvement. It keeps current out of the ESD diodes (often important) and smaller Schottkys (and arrays, if need be) can usually be found. In this case, the resistor divider is the right solution and the OP agrees.

Then why did you pretend it was such a great improvement, in your response to me? It seems you're the one twisting in the wind, John. Now admit that you're full of s*it, or just skulk away. Your choice.

Pre-biased resistors are slick but every time I've considered them, they turn out to be too expensive or a better way to do things shows up (steal part of another circuit). It's hard to beat a MMBT3904 and a couple of resistors (less than two cents).

that's still an inverter, just drawn upside down. .

PNP base to 5V collector to output and resistor ground emitter to resistor to input would work, but not with that part as it has an integral base resistor.

?? 100% natural --- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net

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I'd rather have friends than enemies, but you, with your perpetual need to insult, seem to prefer the opposite.

"SklettTheNewb"

Lots of info here, this thing has taken on a life of it's own. After re-evaluating my requirements against my knowledge/abilities and time constraints I have selected the voltage divider solution: #1 my primary goal was to avoid hardware damage - check! #2 If myself and my team can't read code comments and follow instructions to output 10v then I have bigger issues to worry about.

** The KISS principle applies here.

There are virtually no reasons not to use a simple divider.

You also give Mr Murphy a wide berth too by using a passive solution.

.... Phil

And I'd probably have used a 1K, depending on the output drive of the DAQ.

Cheers! Rich

The best price I got at Digi-Key is .006 for a 1N4148.

Cheers! Rich

The supply providing the 5V for the widget that's input has to be limited to

5V. If the 5V supply has any load (the widget being driven), the supply doesn't have to sink anything.

You're in the habit of adding regulators with no load? Load 'em.

ok lets see, and the +5 is coming from where? Does it have the ability to sink anything coming back to it, like a zener clamp?

I'd had to see that +5 source being supplied from a 7805/78L04 regs or like them. Love the effects of over voltage on other items attached to that circuit! :)

Do pay no attention to me, I just happen to be very observative.

Jamie

Indeed.

Nicely done, Mr. Allison! :-)

JF

use one bit to enable/disable two 7 bit registers, that gives you 14 bits of data. Or use 2 bits to clock 2 6 bit registers, gives 12 bit.

Did you mean "observant?"

But to answer your question, the source of the +5V is left as an exercise for the student. ;-)

Cheers! Rich

Nope, that is exactly what I meant to say, you must remember that I was born and raised in the foot hills of Maine!

If it wasn't for people like us up north, some of the southern boys would be considered impaired! :)

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