DSPSC (look attachment)

[Eshal]

Hello,
Here is a snap.


I want to know its working and its application and its use.

Thank you very much.

 

[chuckey]

The UJT oscillate naturally and turns the triac on and off at a low rate (5 secs on and off) when D8 is not turned on. when the incoming pulses G1 appear they will turn the triac on immediately. So the triac follows the pulses on G1 with a master turn off with G2.
Frank

 

[Eshal]

First of thank you that you replied to my post.

Secondly,
Wait a minute. Can you tell me where is TRIAC and where is D8? Do you mean SCR or D0?

 

[chuckey]

Well the device you called a SCR, but a SCR only conducts when its anode is positive, so it is only used for DC unless there is a diode across it to conduct when the supply goes negative. A triac is like a like a pair of back- to-back SCRs, so it conducts when the supply is positive or negative, so its used for AC.
Frank

 

[Eshal]

OK I got your words that back to back SCRs create a TRIAC. Right?
But my circuit doesn't have TRIAC. And it also not have diode at the gate of the SCR. Do you think there is a mistake in the circuit?

 

[chuckey]

yes, for two reasons, your load is being fed from a transformer, which means that with a SCR, only pulsating DC flows through the transformer secondary. This causes saturation and overheating of the transformer core unless its very big! The other reason is the power conversion, it will vary from 0 to 50% of what the transformer is rated at (ignoring saturation etc). Putting the diode back to back with the SCR will give you 50-100 % of what the transformers ratings (ignoring saturation effects). using a triac will give you 0 to 100% of the transformers rating with no saturation effects.
Frank