Hey everyone, I'm new here so bear with me .... I've got some calculations to do on an SCR firing circuit, I need to determine V_in based on the criteria given in the attachement. I don't know how to solve this circuit, any help is always greatly appreciated. Thanks

J

 

Hey there!!....all you need to know is here

http://forum.allaboutcircuits.com/showthread.php?t=8084

and also here

http://forum.allaboutcircuits.com/showthread.php?t=8075

remember to read first the post cause somebody might have ask before....
i already did....see ya

 

hmmmm, i read your posts but I didn't see any calculations, Im trying to solve for V_in based on the two resistor values and Vcc @ 15v. How do you apply V_gt, I_gt and I_h to solve for V_in. Thanks again.

 

if you have a R680ohms and you need minimum Ig =9mA so…
Vin = 9mA* 680ohms = 6.12V

That’s the voltage you need across the gate and the cathode….to activate the scr....i already prove it in my protoboard...and it works....i triggered a 12VDC Fan motor...so i hope its what you nedd....if not then dont hesitate to post again...see ya

 

heres an schematic of what i did with your circuit....

 

Hey thanks a lot, I wasnt sure.... but that was the value I calculated too (without knowing it ) That really helps, what would the value of Vcc (15v) have to be to turn the SCR off? thanks again!

Jesse