[sergey23 0]

Hello , I have the attached schematics which i am trying to understand the logic of it.
I have a problem understanding J29 and J27 role in opening the V23105A5476A201 relay described in a photo below.
The current suppose to flow from 1 to 16 , so there needs to be voltage drop between legs 1 and 16 to open .
Why leg 1 in J29 connected both to pin16 and pin1 (threw a diode) and J27 leg 1 is connected to leg1 of J29.
What could be the logic of that?
Thanks.
https://eu.mouser.com/ProductDetail/TE-Connectivity-Axicom/V23105A5476A201?qs=KKrrU%252baSadI5%2FocrT%2FYCiw%3D%3D

fff3.pdf

Изменено 12 июля пользователем sergey23

[Yuri7751 25]

https://electronicsarea.com/why-is-there-a-diode-connected-in-parallel-to-a-relay-coil/

[sergey23 0]

Hello Yuri , I have the following part  circuit it uses SCR, the datasheet of the SCR is shown below.
I was told that the scr needs some sort of current to allow the anode connect with the cathode.
U6B and U6A have +12 -12 voltage supply although U6A doesnt show that.
What exactly is this current that is needed ?
why R45 allows for such current for U6B while U6A doesnt allow?
Thanks.
https://www.littelfuse.com/media?re...ittelfuse_thyristor_nyc0102bl_d_datasheet.pdf

[Yuri7751 25]

17 hours ago, sergey23 said:

U6B and U6A have +12 -12 voltage supply although U6A doesnt show that

omg 🙂

This is one chip - two comparators in one package. That's why they are both U6. And pins 3 and 12 provide power to both parts of course. See the datasheet.

[sergey23 0]

Hello Yuri,U6a is a comparator in its data sheet shown below they say that we need a pull up resistor in order for the device to function.
In the diagram in the end the output of the comparator is open collector NPN.

I am trying to think at a comparator as an OPAMP( I know its not).

pullup resistor charges the output to a higher value because we plug the output to VCC

In opamp we dont have such pullup resitor need.

What is unique in opamp that we dont need pullup unlike a comparator?

Thanks.
https://www.ti.com/lit/ds/symlink/lm339a.pdf?ts=1720984171587&ref_url=https%3A%2F%2Fwww.mouser.in%2F

"9.2.2.3 Output and Drive Current
Output current is determined by the load and pullup resistance and logic and pullup voltage. The output current
produces a low-level output voltage (VOL) from the comparator, where VOL is proportional to the output current."

Изменено Воскресенье в 19:44 пользователем sergey23

[Yuri7751 25]

The art of Electronics. P.Horowitz, W.Hill.

An ideal opamp should have a zero output impedance so its output stage is usually a push-pull emitter follower (it provides current gain):

 

[sergey23 0]

Hello,This is important point and maybe there is an error in the logic of this comparator.
My comparator has 12V and -12V supplies.
Basicly if i have only a pullup resistor in the data sheet that meeans the this comparator only works 0V to 12V.
It cannot pull down the voltage so its a basic mistake to put -12V in the supply and think that output could be -12V?
 it cannot bet -12V because we would need some pulling down.
the output for this comparator can be only 0 to12V.
Am i correct regarding the logical error i have?
Thanks.


https://www.ti.com/lit/ds/symlink/lm339a.pdf?ts=1720984171587&;ref_url=https%253A%252F%252Fwww.mouser.in%252F
 

Изменено Вторник в 15:16 пользователем sergey23

[Plain 187]

42 минуты назад, sergey23 сказал:

output for this comparator can be only 0 to12V

Where did you see this in the datasheet?

[Yuri7751 25]

In your case there should be -12V instead of GND (Fig.8-1). That's it. Why don't you use LTSpice?

[_Sergey_ 13]

15 hours ago, sergey23 said:

the output for this comparator can be only 0 to12V.

In such case scrs will never get closed if ones are opened once. Negative gate voltage is needed to close scr after transition to conductive state.