Touch Switch with transistors

Parts List:
Part Description Radio Shack # DigiKey # Notes
R1  22Meg resistor      red red green gold
R2  47K resistor      yellow purple orange gold
R3,R4  100K resistor      brown black yellow gold
R5,R6,R7  2K2 resistor      red red red gold
C1  Capacitor, 22µF, 25V      Electrolytic
C2  Capacitor, 22µF, 25V      Electrolytic
Q1  MPF102      Transistor, NPN
Q2,Q3  2N3565      Transistor, NPN
Q4  TIP31      Transistor, NPN
La1  Bulb, #53      Try others

Couple Notes:
The MPF102 (Q1) can be replaced with a NTE451 or ECG451, but still widely available. JFET-N-CHAN, UHF/VHF AMP
The 2N3565 (Q1/Q2) can be replace with a 2N2222(A), BC107, BC108, BC109(A/B/C), NTE123A, or ECG123A.
The TIP31 (Q3) can be replaced with a NTE196 or ECG196, but is a common type and widely available. NO suffix.

The 'Touch Plate' can be anything non corrosive. I use a silver quarter.

You can also use a small relay instead of the #53 bulb.

The phone number for DigiKey is 1-800-Digi-Key.

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Copyright ©1996 - Tony van Roon