EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: nour on February 15, 2016, 05:13:31 pm
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I have a couple of incidents that I have blown up a microcontroller because of the input/out misusing (by applying high voltage to IO pins :-BROKE)
So I want to add optocoupler isolator to my input/out pins which I am using in my prototyping and learning
the basic Idea is to add optocoupler that can handle switching mosfet/bjt or read input from outside in reasonable speed(not sure how much would that be!)
this is basicly will be for just my development/learning boards, I want them to be idiot-proof :-DD
if there is any better ideas regarding protecting the IO pins please don't hesitate to add yours, may be mine is just too bad or not applicable (I am not an expert after all ;D)
of course I am looking for a cheap optocoupler that I can buy in quantities like 50 or 100 pieces (max :D)
preferable from tme.eu (because they are the cheapest supplier for me right now and the fastest ???)
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That's what I use for my projects:
http://www.tme.eu/en/details/tlp181bl/smd-optocouplers-transistor-output/toshiba/ (http://www.tme.eu/en/details/tlp181bl/smd-optocouplers-transistor-output/toshiba/)
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why this one, do you have a specific reasons also it is expensive to buy 100 piece almost 32 $ :o (that's too much for some optocouplers)
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Oh, maybe that's not good for you. I use them because I don't have to buy them as I desolder them from the unusable boards that I have.
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why this one, do you have a specific reasons also it is expensive to buy 100 piece almost 32 $ :o (that's too much for some optocouplers)
Hi
That's a pretty cheap opto coupler.
What is your price goal?
Bob
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You're unlikely to find very cheap outside of delivery from China.
Cheapest would be aroud 3c each http://www.aliexpress.com/item/50pcs-Pack-PC817-EL817-817-DIP-Optocoupler-Electronic-Accessories-Free-Shipping-A022/32587756016.html (http://www.aliexpress.com/item/50pcs-Pack-PC817-EL817-817-DIP-Optocoupler-Electronic-Accessories-Free-Shipping-A022/32587756016.html)
Depending on your application you could also use resistor + Zenner to ground or resistor + Diode to VCC
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http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1 (http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1)
I just opened the optocoupler page on tme and arrange them asc
can someone tell me about the first 20 if I can choose any of them
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
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I have a couple of incidents that I have blown up a microcontroller because of the input/out misusing.....So I want to add optocoupler isolator to my input/out pins..... basic Idea is to add optocoupler that can handle switching mosfet/bjt or read input from outside in reasonable speed(not sure how much would that be!) I want them to be idiot-proof :-DD.......better ideas regarding protecting the IO pins please don't hesitate....
...looking for a cheap optocoupler that I can buy in quantities like 50 or 100 pieces (max :D)
preferable from tme.eu (because they are the cheapest supplier for me right now and the fastest ???)
There are loads of cheap optos, CNY17 kind of cheap allrounder... Motorola once had a some type of buss isolator chip cant remeber the number.
Why not simply use loads of NPN as I/O. Or buss transivers with open drain.
http://www.tme.eu/se/details/cny17-1-l/optokopplare-transistorutgang-tht/liteon/cny17-1/ (http://www.tme.eu/se/details/cny17-1-l/optokopplare-transistorutgang-tht/liteon/cny17-1/)
Since you dont know your speed use below, else figure out your on/off switch speeds most cheap ones hovers around the usec range anyway.
http://www.tme.eu/en/details/el817/tht-optocouplers-transistor-output/everlight/ (http://www.tme.eu/en/details/el817/tht-optocouplers-transistor-output/everlight/)
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http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1 (http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1)
I just opened the optocoupler page on tme and arrange them asc
can someone tell me about the first 20 if I can choose any of them
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
Hi
The prices on that list are roughly 1/3 of what they are at places I would trust.
Be careful....
Bob
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http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1 (http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1)
I just opened the optocoupler page on tme and arrange them asc
can someone tell me about the first 20 if I can choose any of them
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
Hi
The prices on that list are roughly 1/3 of what they are at places I would trust.
Be careful....
Bob
what do you mean?? :o :o
TME suppose to be one of the trusted places to buy components right? ???
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I think TME is good, lots of people have bought stuff on TME and I haven't heard of an issues yet. Although being from States I have no reason to shop there so I don't have first hand experience with them.
I think if you're dealing with multiple channels you might want to look into multichannel optos to save some money that way.
Quick search at the place I buy components shows this guy: http://www.mouser.com/ProductDetail/Lite-On/LTV-846/?qs=sGAEpiMZZMteimceiIVCBx3Y662pemTNzbYJ80qgGrs%3d (http://www.mouser.com/ProductDetail/Lite-On/LTV-846/?qs=sGAEpiMZZMteimceiIVCBx3Y662pemTNzbYJ80qgGrs%3d)
4 channel for 70c a pop. 11.5c per channel compared to the one listed above. There is also an SMD version which costs 1c more. And you get a pretty nice break if you order in quantity.
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also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
What do you mean by these sentences. speak clear please.
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also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
What do you mean by these sentences. speak clear please.
I thought it was clear enough ???
anyway if someone choose a particular optocoupler I would like him to declare the reasons, what criteria he decided to use to choose this particular part(isolation level, transfer ratio, voltage, extra)
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http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1 (http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1)
I just opened the optocoupler page on tme and arrange them asc
can someone tell me about the first 20 if I can choose any of them
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
Hi
The prices on that list are roughly 1/3 of what they are at places I would trust.
Be careful....
Bob
what do you mean?? :o :o
TME suppose to be one of the trusted places to buy components right? ???
Hi
Ok here is what I mean
90% of the time when you see prices that are 1/3 of the correct prices you are dealing with fake parts or something similar.
Since I have no absolute proof that they are indeed selling fakes, I try to be careful about exactly what I say.
Bob
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I believe that unless you have specific requirements on isolation characteristics, speed, current draw etc.. it doesn't matter so much which you choose. A combined row of them sounds convenient though, and if you only need either output or input it shouldn't be too messy.
As an alternative (depending on isolation requirement of course) I would suggest to have a look at if the micro has clamping diodes on the I/O pins. If so you might get away with a resistor in series as decent protection.
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This is what you asked:
So I want to add optocoupler isolator to my input/out pins which I am using in my prototyping and learning
the basic Idea is to add optocoupler that can handle switching mosfet/bjt or read input from outside in reasonable speed(not sure how much would that be!)
You haven't mentioned any quantitative specification for your need.
I introduced you the solution that I use for the exact situation (Switching transistors with uC). I didn't know the price as I'm using used parts, and It's not important as I use them for my prototype projects. First make things clear with yourself.
PS. Don't ask your questions in a third person way when I'm present here.
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
and I'm still not sure what you meant by "ali family"?!
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Hi
Ok let's back off to some very basic stuff. Opto isolator 101:
These beasts started out as discrete parts. You have an LED that drives a photo transistor. You put a couple of resistors on it and it (sort of) works. It may not be as fast as you need (how fast do you need?). It may not be as low current as you need (?). It may not hit the logic levels you need (?). It's a DC input device. That may be ok (?). It has various breakdown and current limits.
Next up were darlington based parts. They have much better gain. They do not saturate as well. They generally are slower parts.
After that people started making logic output parts. In goes a LED and out comes a CMOS level. Generally more money. Often less fuss. Could be a bit faster than some of the others.
After that the odd stuff starts to show up. Devices that are set up to have well defined transfer ratios for analog applications. Stuff that will drive a TRIAC. Parts with unusual logic outputs (rare).
Throughout all this, you will pay for speed. 150 megabits will be more expensive than 15 megabits. 1.5 megabit costs still less. That keeps on going as your bit rate drops. With some parts the "advertised" bit rate is quite hard to actually get. With a logic output part it might be pretty easy. When there is a single letter between a $15 part and a $1.50 part ... watch out for what you get.
That's a quick walk through. They all have some common features:
Both sides of the coupler need power from somewhere. It may be current in an LED, but it is still power. They all have a voltage isolation spec. It often is dependent on board layout as well. If you *need* 5KV, check the layout requirements.
There is no such thing as a "one size fits all" isolator. One in a really small package will never ever hit a high isolation voltage. A high gain part is not going to be as fast as a good low gain part. Your application will dictate what you need.
Bob
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Unless you need something high speed, EL817 or any other kind of PC817 would be just fine http://www.tme.eu/lv/details/el817/transoptori-tranzistoru-izeja-tht/everlight/ (http://www.tme.eu/lv/details/el817/transoptori-tranzistoru-izeja-tht/everlight/)
Most of other optocouplers will perform about the same. You can safely use them up to about 10-20 kHz frequency.
If you need something with higher speed, price will increase by order of magnitude, H11L1 - H11L3 are among the cheapest http://www.tme.eu/lv/details/h11l1/transoptori-logiska-izeja-tht/fairchild-semiconductor/h11l1m/ (http://www.tme.eu/lv/details/h11l1/transoptori-logiska-izeja-tht/fairchild-semiconductor/h11l1m/)
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http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1 (http://www.tme.eu/en/katalog/optocouplers_112291/#id_category=112291&s_field=niski_prog&s_order=ASC&page=1)
I just opened the optocoupler page on tme and arrange them asc
can someone tell me about the first 20 if I can choose any of them
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
Hi
The prices on that list are roughly 1/3 of what they are at places I would trust.
Be careful....
Bob
what do you mean?? :o :o
TME suppose to be one of the trusted places to buy components right? ???
Hi
Ok here is what I mean
90% of the time when you see prices that are 1/3 of the correct prices you are dealing with fake parts or something similar.
Since I have no absolute proof that they are indeed selling fakes, I try to be careful about exactly what I say.
Bob
They are not fakes, TME is a valid distributor. Those are not "correct prices" but the result of the greed of many other distributors. If the part is actually expensive, it will be expensive at TME too. But if the part is actually cheap, you can get it with much less margin from TME.
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This is what you asked:
So I want to add optocoupler isolator to my input/out pins which I am using in my prototyping and learning
the basic Idea is to add optocoupler that can handle switching mosfet/bjt or read input from outside in reasonable speed(not sure how much would that be!)
You haven't mentioned any quantitative specification for your need.
I introduced you the solution that I use for the exact situation (Switching transistors with uC). I didn't know the price as I'm using used parts, and It's not important as I use them for my prototype projects. First make things clear with yourself.
it is not like I am in a court of law and I faked some facts, it is an open discussion and I have asked about the specs in the second reply, it is not like I came after a 100 entries and out of the blue changed the topic to how car engine works ???
please be more flexible, and it is not like I am questioning you, you have added your valuable reply, so thanks for the information, if you want to enrich me with more knowledge, I will be happy to listen from you
PS. Don't ask your questions in a third person way when I'm present here.
also can someone please tell me why he chosen whatever he have chosen
I mean what is the criteria?
No ali Family please :-//
and I'm still not sure what you meant by "ali family"?!
calm down man I feel heat in the talk, you think you are the only person in the topic, I have wrote this talking for every person who might write reply later, I didn't mean by (he) you :palm:, I meant the person that will add entry in general not you
about ali family I will let you discover this yourself ;D
use google and you will someday know what I am talking about (or read the member's replies in order and you will understand)
Hope I have cleared any misunderstanding :-//
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Hi
Ok let's back off to some very basic stuff. Opto isolator 101:
These beasts started out as discrete parts. You have an LED that drives a photo transistor. You put a couple of resistors on it and it (sort of) works. It may not be as fast as you need (how fast do you need?). It may not be as low current as you need (?). It may not hit the logic levels you need (?). It's a DC input device. That may be ok (?). It has various breakdown and current limits.
Next up were darlington based parts. They have much better gain. They do not saturate as well. They generally are slower parts.
After that people started making logic output parts. In goes a LED and out comes a CMOS level. Generally more money. Often less fuss. Could be a bit faster than some of the others.
After that the odd stuff starts to show up. Devices that are set up to have well defined transfer ratios for analog applications. Stuff that will drive a TRIAC. Parts with unusual logic outputs (rare).
Throughout all this, you will pay for speed. 150 megabits will be more expensive than 15 megabits. 1.5 megabit costs still less. That keeps on going as your bit rate drops. With some parts the "advertised" bit rate is quite hard to actually get. With a logic output part it might be pretty easy. When there is a single letter between a $15 part and a $1.50 part ... watch out for what you get.
That's a quick walk through. They all have some common features:
Both sides of the coupler need power from somewhere. It may be current in an LED, but it is still power. They all have a voltage isolation spec. It often is dependent on board layout as well. If you *need* 5KV, check the layout requirements.
There is no such thing as a "one size fits all" isolator. One in a really small package will never ever hit a high isolation voltage. A high gain part is not going to be as fast as a good low gain part. Your application will dictate what you need.
Bob
thanks a lot for your reply, you have cleared some misunderstanding for me about those small devices, I think I will reconsider choosing with another standards
I think I will probably end up buying 2 or 3 categories
High speed with-in megabits --> will be expensive which means I will buy small quantities
low speed for slow applications that require switching with the range of 10 khz or less
Hi
Ok here is what I mean
90% of the time when you see prices that are 1/3 of the correct prices you are dealing with fake parts or something similar.
Since I have no absolute proof that they are indeed selling fakes, I try to be careful about exactly what I say.
Bob
yes I agree with you, but that apply to place like ebay, amazon and of course aliexpress, but not for will known distributor like TME
I have bought from them several times, they are very good, may be not enough to be 100% sure but I can for sure say they are good(hopefully ^-^)
I actually do this all the time when buying from ebay, if for example saw some item being sold on say digikey with 49 $ and on ebay you can get it with less than a 1$ :o at this moment I will just close my eyes and pretend I have never seen this item before :-DD
here is an example with LM338
from digikey
http://www.digikey.com/product-detail/en/LM338K%20STEEL/LM338K%20STEEL-ND/6224 (http://www.digikey.com/product-detail/en/LM338K%20STEEL/LM338K%20STEEL-ND/6224)
from Chinese seller from ShenZhen, china
http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
and you have all the freedom in the world to guess what they have added inside the IC package :-DD :-BROKE
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from Chinese seller from ShenZhen, china
http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
and you have all the freedom in the world to guess what they have added inside the IC package :-DD :-BROKE
Some are original parts but salvaged from old gear.
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from Chinese seller from ShenZhen, china
http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
and you have all the freedom in the world to guess what they have added inside the IC package :-DD :-BROKE
Some are original parts but salvaged from old gear.
may be but the list is declared as NEW
have you tried this one before ?
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from Chinese seller from ShenZhen, china
http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/311418393584?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
and you have all the freedom in the world to guess what they have added inside the IC package :-DD :-BROKE
Some are original parts but salvaged from old gear.
may be but the list is declared as NEW
have you tried this one before ?
Haven't tried this particular part. But that's been my experience with some components from China. If it's significantly lower in price it's either fake, salvaged, or just a surplus that made it into the gray market. But more often than not the first two.
I am familiar with Alice11... seller on Ebay. He's quite famous. Sells a lot of goods.
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this particular item from this particular seller is fake down to the bottom of the ocean of fakeness >:(
I have once bought this LM338 from him, I bought like 5 or more, I don't really remember, was long time ago
guess what ;D, when building the circuit it will work just great but the moment I put any noticeable load on the output it stop working instantaneously and forever :o
I remember the printing on the package was easily removed by just scraping it by your fingernail :-DD
of course I just throw all of them away in the garbage never bother test all of them actually and from that moment I have learned my lessons and do my homework before buying from any seller, at least from china
it was a real waste of time and money |O