guys i want to find values for R2 and R3 in following circuit diagram.is there any equation or method i can use to find this two values? (i was able to calculate R1 and C)
thanks
guys i want to find values for R2 and R3 in following circuit diagram.is there any equation or method i can use to find this two values? (i was able to calculate R1 and C)
thanks
helo thank you but is the equation used there to find R2 is always applicable?
according to it
Solution: Although R2 is not needed, the “Motorola Engineers Report ” suggests
that we should st il l use it and i ts value can be approximated as
R2 = 0.015hR V = 0.015× 0.6×10,000× 20 = 1800W
this eqation is according to motorola engineers report.and he havent specified for what UJT is this equation applicable.I'm using 2N2646 UJT and would like to know if this equation is applicable for it
thanks again
helo thank you but is the equation used there to find R2 is always applicable?
according to it
this eqation is according to motorola engineers report.and he havent specified for what UJT is this equation applicable.I'm using 2N2646 UJT and would like to know if this equation is applicable for it
thanks again
well according to data sheet η value is given for V(b1b2)=10v but valley current and peak current is given for 20v is it okay to use these values in a circuit operated in 10v without regarding about each parameters voltages?
or do i have to get peak current for 10V?
well according to data sheet η value is given for V(b1b2)=10v but valley current and peak current is given for 20v is it okay to use these values in a circuit operated in 10v without regarding about each parameters voltages?
or do i have to get peak current for 10V?
can you tell me how to calculate voltage in R3 resistor? (i want to drive opto coupler through R3 output and ned to calculate resistor value i need to use in series with opto coupler) thanks
I know. I was just trying to point out that the UJT is used for firing a SCR. You should use a DIAC to fire a TRIAC instead. Or use an optically triggered TRIAC to fire the main TRIAC. You can get them with zero crossing built in too. This would make the value of R3 irrelevant.
Did you look at the UJT link I posted, it has all the formula you need.
Make R3 about 27R thru 47R to drive a SCR gate or about 100R to 150R for an opto coupler.
The reason why there are so few UJT/Triac dimmer circuits is because its not an easy way to sync with zero crossing for full wave control of the triac/lamp brightness.
Consider this, somehow you will need to full wave rectify the mains frequency at a voltage level suitable for a UJT emitter/base's
From the rectified pulses you will have to generate a ramp to drive the UJT base Res/Cap so that you vary the trigger point on the mains cycle and so on............its not worth the hassle.
I agree with kchriste, for a simple dimmer use a DIAC.