All About Circuits Forum the circuit of SCR with 0-180 degree firing angle
 Register Blogs FAQ Members List Today's Posts Search Today's Posts Mark Forums Read

 Homework Help Stuck on a textbook question or coursework? Cramming for a test and need help understanding something? Post your questions and attempts here and let others help.

#1
03-21-2012, 02:38 AM
 qtlj657 New Member Join Date: Mar 2012 Posts: 7
the circuit of SCR with 0-180 degree firing angle

it's about SCR with 0-180 degree firing angle circuit.
i can't figure out the function of the two 1N4004 Diode

Last edited by qtlj657; 03-21-2012 at 03:01 AM.
#2
03-21-2012, 10:49 AM
 jimkeith Senior Member Join Date: Oct 2011 Location: Pennsylvania Posts: 538

This is a very curious circuit--at first, I did not believe that it would even work.

Then I looked up the specs on the 2N5064 --it is a sensitive gate SCR with 200ua gate sensitivity.

The circuit is a real mind-bender.

How it works is the capacitor gets charged negatively via the 1N4001 that points up--the 1N4001 that points right keeps current from flowing reverse out of the SCR gate. The delay occurs as the capacitor must charge to a positive voltage before there is gate current. It appears that there may be much 'dead range' in the 2.5M pot as settings above about 100K will not provide sufficient gate current to trigger the SCR--unless, of course, the actual Igt is much lower than spec, and that is possible.
#3
03-21-2012, 01:33 PM
 qtlj657 New Member Join Date: Mar 2012 Posts: 7

actually. it works.. i did work it out in the lab.

it's a lab about comparing two SCR circuit, one is 0-90 degree firing angle and the other is 0-180..

what you say is just i wonder.

in the lab i adjusted the rheostat all the time.. is it the reason the capacitor got charged?

i think the right hand side 1N4004 is blocking the possible negative current from the Cathode flowing back to gate.
#4
03-22-2012, 01:44 AM
 jimkeith Senior Member Join Date: Oct 2011 Location: Pennsylvania Posts: 538

Quote:
 Originally Posted by qtlj657 in the lab i adjusted the rheostat all the time.. is it the reason the capacitor got charged? i think the right hand side 1N4004 is blocking the possible negative current from the Cathode flowing back to gate.
Do not understand your first question.
Yes, this the 1N4004 prevents negative gate current--and negative load current.

Last edited by jimkeith; 03-22-2012 at 03:33 AM.

 Tags angle, circuit, degree, firing, scr

 Related Site Pages Section Title Worksheet Opamp oscillator circuits Worksheet Thyristors Worksheet Performance-based assessments for semiconductor circuit competencies Worksheet Thyristor application circuits Textbook The Silicon-Controlled Switch (SCS) : Thyristors Textbook The Unijunction Transistor (UJT) : Thyristors Textbook The TRIAC : Thyristors Textbook Field-effect-controlled thyristors : Thyristors Textbook The Silicon-Controlled Rectifier (SCR) : Thyristors Textbook Thyristors : Solid-state Device Theory

 Similar Threads Thread Thread Starter Forum Replies Last Post louie55 The Projects Forum 15 02-03-2012 12:41 PM mohamed.hassan General Electronics Chat 1 01-14-2011 04:56 PM gsugumaran General Electronics Chat 2 12-10-2010 12:29 PM jboulasii General Electronics Chat 5 08-21-2009 09:22 PM will1234 General Electronics Chat 5 11-19-2007 12:55 AM

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Electronics Forums     General Electronics Chat     The Projects Forum     Homework Help     Electronics Resources Software, Microcomputing, and Communications Forums     Programmer's Corner     Embedded Systems and Microcontrollers     Computing and Networks     Radio and Communications Circuits and Projects     The Completed Projects Collection Abstract Forums     Math     Physics     General Science All About Circuits Commmunity Forums     Off-Topic     The Flea Market     Feedback and Suggestions

All times are GMT. The time now is 01:07 PM.