basic electronics

As power is first applied, the piezo is drawing a lot of current through R1 & 2 and shunts it away from the base of the transistor. At some point, as the piezo begins to saturate, the shunting effect diminishes to the point where the transistor starts turning on. This starts discharging the [...]

Comparators can be made to perform a basic memory function by wiring them as a ‘SET / RESET’ type of FLIP/FLOP. This type of circuit can be used in unplugable walk around throttles to remember the direction of the train when the controller is disconnected. In the next diagram the comparator will remember which switch [...]

Parts:
R1,R3____________1K 1/4W Resistors
R2,R5___________10K 1/4W Resistors
R4_____________220R 1/4W Resistor
R6_____________220K 1/4W Resistor
R7______________22K 1/4W Resistor
R8_____________100K 1/4W Resistor
C1,C2___________22µF 25V Electrolytic Capacitors
C3______________10nF 63V Polyester or Ceramic Capacitor
C4______________47µF 25V Electrolytic Capacitor
Q1,Q2_________BC557 45V 100mA PNP Transistors
Q3____________BC337 45V 800mA NPN Transistor
SW1___________SPST Toggle or Slide Main Switch (See Notes)
P1____________SPST Pushbutton [...]