You can make a Toggle Touch Switch with Two Inverter Gates, two
resistors, and two capacitors. The schematic diagram of the circuit is
shown in the figure below. At power up, the output (of U1A) will be
high, and the inverting output will be low because U1A gate will be
triggered to ground level by C2. After triggered, the low level of U1A
input is maintained by U1B output via R2.
If we touch the pad at this condition, where the output is high, then
the U1A input will go high because we “short” the voltage of C1 to the
input pin, and the low level previously caused by low level of U1B
output voltage connected via R2 can’t be maintained because our skin
resistance is much lower than 10M.
After U1A input goes high then U1A output will go low, and now U1B will go high to maintain high voltage level of U1A via R2, so we can release our finger without loosing the last state. Touching the pad again after we release our previous touching will toggle the output as the condition is reversed.
After we touch the pad, we have to release before 1 second (R2C2 time constant) elapsed. If we touch the pad longer than R2C2 time constant then the output will oscillate (about 1 Hz).
After U1A input goes high then U1A output will go low, and now U1B will go high to maintain high voltage level of U1A via R2, so we can release our finger without loosing the last state. Touching the pad again after we release our previous touching will toggle the output as the condition is reversed.
After we touch the pad, we have to release before 1 second (R2C2 time constant) elapsed. If we touch the pad longer than R2C2 time constant then the output will oscillate (about 1 Hz).
