In figure 1 we have an ultra-simple continuity tester in which the "super-transistor" is used to excite an LED.
Figure 1 - continuity tester
The sensitivity of this circuit is very great, so that resistances of the order of megohm can be indicated as continuity and the current in the probes is extremely low. The LED is red and the device can be easily mounted on a printed circuit board, as shown in figure 2.
Figure 2 - Mounting board | Clique na imagem para ampliar |
Material list
Q1 - BC517 - Darlington transistor
LED - Common LED of any color
B1 - 6 V - 4 batteries
S1 – On/off switch
R1, R2 - 100 k ohm - resistors - brown, black, yellow
R3 - 1 k ohms - resistor - brown, black, red
Several:
Battery holder, printed circuit board, test leads, wires, etc.
