Hello Misterbill2, Thank you for the good responce.
I am trying to understand it in detail:
" The abs max current, above that is assured destruction, is 60 mA. ":

Yes the diode of the optocoupler will byrn at 60mA according to the datasheet bellow.

"for TEN milliamps , 1200 ohms is reasonable. For a bit over 20 milliamps a 560 ohm (Green, Blue, Brown is a correct choice."
How did you decide that 1200 pullup resistor of the comparator will give 10mA?
How did you see that 560 pullup resistor is a good choise for Blue LED?

 

My error!! I was not thinking of a blue LED. I was thinking about the opto-coupler LED. In post #19 you were mentioning the opto-isolater LED. AND that is what the chart with the red arrow is about. If D3is a blue diode it is certainly not the one in the opto-isolator..

BUT REALLY, none of that matters because the devices tagged to be COMPARATORS are drawn with the symbols for OPTO devices. AND the pin numbers are totally incorrect for what the tags identify them as being. When needing to communicate with us it is important to use the correct symbols. That is important,

 

Hello Mister Bill,The symbol is a netlist and not a real chip,if we talked purely theoretical.
based on the500Ohm pullup do you think 14.8mA will be a problem from each comparator?(based on the calculation below)
Thanks.

Vf + LED Vf (1V + 3.6V) = 4.6V
(12V - 4.6V) / 500 = 14.8mA

 

I need to shut down M1 mosfet with the optocoupler .
for that I need the optocoupler work properly .
The Vce of the optocoupler is the Vsg of the mosfet .
I changed the zenner diode into 5.1V so it will get close to 5V need for CNY17-3 according to its datasheet.

but when I open all 3 comparators I get 40mA and -40mA at some points as shown below of its diode on the left side of the CNY17-3.

Vce=5V tells me about the optocoupler CTR .
How can I see the current needed on both side of the optocoupler?
photos and ltspice are attached.
Thanks.

 

Since the main voltage is not shown, and since I do not open .ZIP files, the value of resistor to drop the current down is a challenge to know. With what I guessis a zener diode across the opto isolator it does not seem that the mosfet can ever be cut off.

 

Hello . Main_V is 50V I am trying to turn on and off the current supply from main_V using optocoupler and mosfet.

zenner diode is reversed biased only when optocoupler is off.

the thing is the current in the optocoupler .
from the simulation I have 8mA on the collector.
Given the CNY17-3 datasheet in the link ,how can I know the needed current to flow on both sides of U8? so it wont burn.
Thanks.
https://www.vishay.com/docs/83606/cny17.pdf

 

LTspice simulation file is attached.

Please post your asc file directly, not zipped.

 

The data sheet shows the maximum collector current for the opto's transistor as 50 mA steady, and the Maximum C to E voltage as 70 volts.
A reversed bias is the normal way to use a Zener diode, That is when it allows it's rated voltage to develop, at some specified current level.

 

Given the CNY17-3 datasheet in the link ,how can I know the needed current to flow on both sides of U8?

If the collector current is 8mA (I make it ~50V/6.8kΩ =~7mA when the opto-transistor is switched on fully) and the CTR is its worst-case value of 100% then the opto-diode needs 7mA at least.
How much current do you hope to switch with that particular mosfet? Are you aware of its tiny size?

 

Hello Alec_t, My simulation has simbols and spice files thats why I zipped them together.
I uploaded the files separately but it limited to 10.
74ABT04_Test_ABCD_golden_08_12_25_with_delay_with_protection.asc is the main simulation file.

500 Ohm pullup makes too much current .few question:
1.The collector current is 8mA in the simulation ,How do I know the needed current in reallife?
2.I can increase the pullup to lower the current from each comparator but if I assume all 3 comparators will be ON and I do 8mA for 3 comparators, then in real life when one comparator will be open then the optocoupler would not shortshut dow the current going threw the mosfet becausethe input IF current is too low.
How todesign it so The optocoupler will shutdown the current both when 3 comprators are HIGH and in the case wher only 1 comprator is HIGH?

3.I was to that LM339 20mA sourcing is almost maximum, but LM339 is not sourcing at all (its floating output)the Vpp threw pullup is sourcing.
Why its a problem?
Thanks.

 

If you look at the actual LM339 data sheet, and understand the internal arrangement of the LM339 comparator,, you will see that it has an OPEN COLLECTOR output. What that means is that THE LM339 can ONLY SINK current.

The LM339 is a quad comparator IC with 14 pins, so the 5 pin image you have IS TOTALLY INCORRECT IN EVERY ASPECT !!
Somehow you have been given incorrect information, and evidently an incorrect model as well.

I suggest visiting an IC manufacturer's website to get the correct information about the devices you want to use.
Others here can tell you which websites can be trusted, which is vital, because it seems there are a lot of incorrect sources on the web.