How does a diac DB-3 circuit work?


How does a diac DB-3 circuit work?

The working of this circuit is pretty simple, and the critical switching job is handled by the diac DB-3. When evening sets in, the light on the LDR starts falling, which causes the voltage at the junction of R1, DB-3 to gradually rise, due to the increasing resistance of the LDR.

Why do we use DIAC in a TRIAC circuit?

If you want a TRIAC to conduct you need to provide a positive or negative pulse to the gate, in order to provide symmetric firing the DIAC are mostly used along with the TRIAC circuit. The DIACs are used for triggering TRIAC or other kinds of thyristors, apart from this they do not possess many applications.

What voltage is needed to turn on a diac circuit?

An voltage of around 35 volts dc or peak ac is applied which switches ON the diac into conduction, due to which a current of around 14 mA begins flowing through the output resistor, R2. Specific diacs may possibly turn on at voltages below 35 volts.

How many terminals does a diac have?

As mentioned earlier the DIAC has two terminals namely MT1 and MT2 and it can deliver current flow in both directions. The DIAC is made of a five-layered structure; the layers closer to the terminals are the combination of both positive and negative layers.

What is a db3/db4 trigger diode?

Functioning as a trigger diode with a fixed voltage reference, the DB3/DB4 series can be used in conjunction with TRIACs for simplified gate control circuits or as a starting element in fluorescent lamp ballasts.

What is a diac trigger circuit?

The diac circuit in the following implementation is a phase control process which can find many applications other than triac control, in which a variable phase pulse output may be necessary. Figure above displays typical diac trigger circuit.

What happens when the DIAC is switched on?

Once the diac is switched ON, decreasing the supply voltage through the potentiometer has no effect on the diac. However, after reducing the voltage through the potentiometer, the reset switch S1 could be used for toggling OFF the diac conduction and reset the circuit in the original switched Off condition.