Electrical Projects With the advent of inexpensive, physically small electronic control devices, more and more small appliance manufacturers can be expected to use them in their designs. You have already seen how one such device, a diode, is used to convert ac into dc. There are many other small electronic components which can be used in the control circuitry of appliances and tools.


Silicon Controlled Rectifier (SCR). Like the more conventional rectifier diode, this device will permit electrons to flow in only one direction—from the cathode to the anode, against the arrow.

However, an SCR also has a third connection to it, the gate. Unless the gate is activated by a small voltage, no current will flow in the circuit. No current will flow because the SCR is not receiving any gate voltage. However, when S2 is closed electrons will flow through the diode in the direction of the arrows.

Even though S2 is opened again, current will still continue to flow through the SCR. Once enabled by the gate voltage, the diode remains "latched" open, until switch SI is opened momentarily. Then current will not flow in the circuit until SI is again closed and S2 is closed momentarily.




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Home > Electrical Projects > Tools And Components > Solid - State Devices

August 20, 2008