hey guys. SO i've been given the assignment of designing and building a dimmer for a 40watt 120v bulb using 2 SCRs. A triac would be nice, but no, must be SCRs.

So i made the triac equivilant lol.

Now in multisim, stuff works using the "virtual" parts. However, i can only get an output voltage on the meter of 0-65V

So when i try to substitute in real parts in Multisim, i get about 20 minutes of convergence errors, followed by a circuit that sits at 66V across the light bulb and responds to no control. My guess is, i've picked the wrong parts, OR, i've wired something wrong. Can someone point me in the right direction?

Ive found by varying the 2 capacitor values i can set my "start" voltage essentially. The bulb says 100W, but, i can't change it. Should be 40W. My sine wave phase shifts nicely.

Thanks in advance guys.

 

any reason you could not put the whole circuit (minus load and AC power) inside a bridge?
http://www.thefullwiki.org/Dimmer
http://www.free-circuit.com/2009/06/28/ac-voltage-light-dimmers-circuit-with-scr/#comment-1898
http://www.8085projects.info/post/Simple-SCR-dimmer-circuit.aspx

 

Panic mode, no, i dont beleive there is no reason i cant use a bridge. Thanks for the resources! Ive got simulations to do.

 

Panic Mode,
I have simulated the given circuits and boy are the output wave forms messy! If i simply sub in a triac, life is well.

Are these supposed to be full range? Ie 0-Full 120v?

Im at the point to stop asking questions and start building and playing to see what happens.

Thanks!

 

it's just phase angle fired SCR. does not matter how delay is created as long as covers T/2. SCR works double duty here and runs each half-period rather than every other.

 

Your circuit wont work , you cant connect both gates together, they have to be driven separately, as each thyristor will bias the other on, better with a triac.