electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  Twyndyllyngs Live Chez Mosc

poster

Please visit the chat
 Forum index » DIY Hardware and Software » Arduino
Protecting pins doubth
Post new topic   Reply to topic
Page 1 of 1 [6 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
MapacheRaper



Joined: Feb 15, 2018
Posts: 117
Location: Spain

PostPosted: Thu Nov 22, 2018 5:19 pm    Post subject: Protecting pins doubth Reply with quote  Mark this post and the followings unread

Im building some arduino circuits and I want to protect the pins from the eurorack voltages. I see most circuits use a resistor and then a 5v1 zener connected to ground.

In other schematics I see 2 schottky diodes. One between pin and ground and another between +12 and pin.

Are all correct?. I guess the double schotkky gives more protection, isn´t?

Why 5v1 zeners and no less?.

I would like to give all the possible protection to my circuits, but if just one 5v1 zener is enoght, why to put 2 schottkis?
Back to top
View user's profile Send private message
Blue Hell
Site Admin


Joined: Apr 03, 2004
Posts: 22598
Location: The Netherlands, Enschede
Audio files: 224
G2 patch files: 319

PostPosted: Thu Nov 22, 2018 6:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Often input pins are specified to be able to tolerate input voltages between Vee / Vss (usually ground) - 0.3V and Vcc / Vdd + 0.3V. Now when your Vcc / Vdd is 5V a 5.1 zener would handle positive overloads, but the dual schottkky would do it for all Vcc / Vdd values and for negative overloads too. Sometimes on 3V3 devices inputs may be 5V tolerant - so in that case the zener thingie could work.

One caveat .. the zener will protect against positive over voltage, but for reversed current it acts as a silicon diode, giving a .7V drop .. so the zener solution does not protect too well for negative overloads. This can be mitigated though with a current limiting resistor between the zener and the input.

It's less thinking to just use the schottkys .. as long as the tolerated over voltages are -0.3V / +0.3V. And usually the the zener solution when needing to protect against negative over voltage would need an extra resistor.

hope this is not too technical?

_________________
Jan
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1717
Location: West Red Spot, Jupiter
Audio files: 195

PostPosted: Thu Nov 22, 2018 8:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Schottky diodes are very fast switching diodes. When the module is not being abused by an over-range signal, both of the diodes are reverse biased (off) and do nothing. When the signal goes bad, one diode turns on and you want that to happen as fast as possible. The protection circuit is called a "diode clamp" which describes what it does. When the diode turns on, it will conduct whatever current is available from the source signal, so the diodes need to be able to conduct at least that much current. I like to make things like that 15% or more larger than expected demand. If the diode blows, it's no longer doing it's job.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Grumble



Joined: Nov 23, 2015
Posts: 833
Location: Netherlands
Audio files: 27

PostPosted: Fri Nov 23, 2018 1:25 am    Post subject: Reply with quote  Mark this post and the followings unread

http://electro-music.com/forum/topic-68022.html

Long story short: as long as you use a resistor at the in/output of about 1k the internal schottky diodes will provide sufficient protection, no need for external diodes.

_________________
my synth
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1717
Location: West Red Spot, Jupiter
Audio files: 195

PostPosted: Fri Nov 23, 2018 7:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, I've been able to blow internal CMOS ESD diodes. If that happens on a 40106, no big deal, but if it's a CPU, it's more expensive. Just saying that a few cents worth of external diodes can be more than worth both the monetary cost as well as the PITA factor of blown internal diodes.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
MapacheRaper



Joined: Feb 15, 2018
Posts: 117
Location: Spain

PostPosted: Sat Dec 01, 2018 6:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Sorry for the delay in response, for some reason I haven´t received notifications of new posts in this thread.

That´s the perfect balance between technical and common sense... Thanks for the answers!

But I must confess that I still not sure of what is the correct way. (Does even exists a correct way??). I guess 1k plus a schottky would do the trick. Definitively I don´t want to blow the processors.

Im going to re read slowly till I grasp it. Thanks again, maestros!

Edit: Afetr re-read and going thru the "torturing the arduino pins with -17V plus 1K resistor" thread now I think I will sleep better. If the can handly it, for sure they will handle standard eurorack voltages (with a 1k resis) with no problem
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic
Page 1 of 1 [6 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Arduino
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use