ESD protection for bi-directional digital I/O

Other Hardware Sensors
1

I am going to connect the DS18B20 temperature sensor to my Arduino. The device has its +5 vdc and ground leads and a single bi-directional data lead that connects to the I/O pin. The data lead is pulled high with a 4.7k resister. Very standard circuit.

This will be used in a commercial, albeit small, spirits still. How do I provide protection for the Arduino from industrial mayhem?
I would love to use opto-isolation, but I don't know how to do it with a bi-directional data lead. I can connect a 5.6 volt zener between the data lead and ground, and while in theory this should provide some protection, I suspect this is not great or you would see it taught everywhere.
I have also just learned about a TVS diode array made by Littelfuse (SP724AHTG) ($1.49) that will clamp the voltage on a data line between the +5 and ground power supply voltages. Its input connects to the data lead and it connects to the power supply leads. It doesn't care which direction data is going. Is this the best way for me to go? Or, is there a better answer out there?

Thanks,

Barry

2

So, are you looking for a system to protect your chip?
You can use one or two schottky diodes on the input pins to protect for over voltage.

3

Yes, I am looking for a way to protect the Arduino chip from spurious crap on this bi-directional data lead.

4

To protect from over/under voltage damage, you can use two schottky diodes on each input. such as
http://www.google.com/imgres?imgurl=http://m.eet.com/media/1172886/fig3.jpg&imgrefurl=http://www.edn.com/design/analog/4399004/Key-benefits-of-input-over-voltage-protected-op-amps-in-systems&h=410&w=537&sz=14&tbnid=gtXtcifiSJ4B2M:&tbnh=90&tbnw=118&zoom=1&usg=__FuaG5BtufSEZW43vwam9WPna4Y4=&docid=9QajVBKi9Bax5M&sa=X&ei=53YmUpzlA4nD2QX14IHQBg&ved=0CEUQ9QEwAw&dur=14328

5

The DS9503 is recommended for one-wire protection.

6

Well the DS9503 certainly looks much better than a garden variety zener and it appears to be designed for the very data lead I am dealing with.
I wonder if it is better than the Littelfuse device identified in my original post?

7

You are not confusing a schottke with a

garden variety zener

are you? Where did the zener idea come from anyway?

8

Zener diodes are commonly used to clamp a circuit node to a voltage. I use them in making power supplies for 1920s battery radios. In this case my supply is +5vdc above ground so a 5.6 volt zener will clamp the voltage at 5.6 and not let it rise above that. The symbol in the circuit you noted is for a zener diode. I don't know whether they make Schottky zener diodes or not and I am not aware of a symbol for a Shottky type diode.

9

@oldradio, yes, you are right. That symbol was for a zener diode. My error. Still, you may want to look into using schottky diodes for over voltage protection. Sorry for the confusion.

10

oldradio:
I would love to use opto-isolation, but I don't know how to do it with a bi-directional data lead.

http://www.merl.com/papers/docs/TR2003-35.pdf

11

With a one-wire network? I'd be impressed if you could make that work.

12

It would take more time than I have to make the bi-directional LED communications method described in the paper work. It seems to require two I/O pins which may not work with the one I/O pin used by one-wire. Also, there might be some data rate issues.
Interesting idea though!