Problem with triac model in LT Spice XVII

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cfuqwawijhkutnddca

Joined Apr 4, 2020
1
Hi, I've got problem with my project. I want to make dimmer. R6 is a photoresistor (I made a function), but the triac is not working like it should. R8 is Light bulb. I took the directives from educational examples dimmer, but the current is so low.
 

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ericgibbs

Joined Jan 29, 2010
12,449
hi cf,
Welcome to AAC.
Other than the Ground/Common node on R8, which other node of the circuit can be considered as 0V reference.?
There is a Triac Lib in LTSpice.
E


Edit:
Who designed the circuit, there are a number of problems.
 
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gryzmol

Joined Apr 10, 2020
11
hi cf,
Welcome to AAC.
Other than the Ground/Common node on R8, which other node of the circuit can be considered as 0V reference.?
There is a Triac Lib in LTSpice.
E


Edit:
Who designed the circuit, there are a number of problems.
I'm sorry for using another account. I'm a student and this is my project for one of my courses. I used already made board and schematic from a website, that sells the DIY PCB, but I need to make my own simulation and I don't know what is wrong with the current one. It works only when I change them in the directives on the left (.param R) 1e6 to conduct and 2k to block. It doesn't work for the photoresistor
 

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Alec_t

Joined Sep 17, 2013
11,997
Since this is Homework, tell us what alternatives you have tried.
Have you read the datasheet for the triac, to ensure the circuit can always supply enough gate current to turn it on?
 

gryzmol

Joined Apr 10, 2020
11
Since this is Homework, tell us what alternatives you have tried.
Have you read the datasheet for the triac, to ensure the circuit can always supply enough gate current to turn it on?
I tried a lot of libraries, diffrent triacs, changed the parameters of the resistors R7 and R3 to make it work.
It is already a made circuit to buy. I just wanted to make the simulation in Spice, but I don't know where is the problem.

From what I see the current is too low for the Q1, so i thought that's cause of the resistor, but changing the values doesn't make a difrence.
 

Alec_t

Joined Sep 17, 2013
11,997
It worked for me in LTspiceXV11 (I don't have LTS1V any more), using a different triac (one from Teccor, not ST). The triac started firng after the caps had charged up, i.e. after about 5 secs.
I found the ST models caused the sim to freeze.
 
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