SCR Tester

This handy tester will provide a visual "on" or "off" switching and latching indication. When finished, you can test all those posible 'duds' in your junkbox and dump some of those in the garbage. If the scr is latching and can hold the latch it is most likely okay.

Look at the circuit diagram, it shows a 3-amp, 50-volt SCR (under test) and a test circuit. Points "Gate" and "Kathode" are temporary connections, so that they can easily be opened. I used toggle switches for each, but use whatever you feel comfortable with, a simple jumper wire would do the trick. I use this gadget in my shop and so have it mounted in a small case. This circuit can even be bread-boarded for your purpose.

When "Kathode" is closed, the lamp doesn't light. When "Gate" is also closed, the lamp lights to its full intensity. The lamp remains lit even if "Gate" is opened again. But when "Kathode" is opened, even momentarily, the lamp does not close again when "Kathode" is closed. That illustrates the "ON" and "OFF" operation of the SCR.

I tested the following SCR types: C106D1 (400V/4A)     
                              T106Y1 (30V/4A)
                              C106F (50V/4A)        
                              C106F1 (50V/4A)
                              C106B (200V/4A)      
                              CSM2B2 (100V/4A)
                              T106D1 (400V/4A)     
                              NTE5402 (100V/0.8A)
                              TIC106M (600V/8A)    
                              NTE5457 (400V/4A)
                              TIC126M (600V/25A)   
                              CR6AM-8 (400V/10A)
                              MCR106-3 (100V/4A)   
                              NTE5455 (200V/4A)
         
In all cases the tester was accurate in telling 'good'
from the 'bad'.

DC circuit equations and laws

Ohm's and Joule's Laws

NOTE: the symbol "V" is sometimes used to represent voltage instead of "E". In some cases, an author or circuit designer may choose to exclusively use "V" for voltage, never using the symbol "E." Other times the two symbols are used interchangeably, or "E" is used to represent voltage from a power source while "V" is used to represent voltage across a load (voltage "drop").

Kirchhoff's Laws

"The algebraic sum of all voltages in a loop must equal zero."

Kirchhoff's Voltage Law (KVL)

"The algebraic sum of all currents entering and exiting a node must equal zero."

Kirchhoff's Current Law (KCL)

From electronicsteacher