Delayed Turn-On Switch With SCR (ART313E)

High-sensitivity SCRs (TIC106, MCR106, and others) can be triggered from very low currents. This means that high-value resistances in RC circuits can be used to delay the tum-on point of an SCR.

Using a 100 k resistor in the circuit shown by Figure 1, we can delay the tum-on instant of an SCR for up to several minutes. The resistor can be replaced with a 100 k variable resistor in series with a 1 k resistor if the reader needs to adjust the time delay. To turn off the circuit, SZ is used. The circuit can also be turned off by switching off the power supply voltage.

 

Figure 1 – Delayed Turn-on switch
Figure 1 – Delayed Turn-on switch