The power field effect transistors (Power MOS) can control intense currents from extremely low currents applied to the gate, given their very high input impedance.
In these conditions, the current passing through the fingers of a touch sensor is insufficient to cause shock, but you can switch relatively large loads with many ampères currents by turning them on or off easily.
The circuit given in figure 1 can control loads of several amps, depending only on the MOSFETs used. The voltage should be 6 to 15 V, observing that there is a voltage drop in the transistor.
Of course, the power supply must be isolated from the power grid if no battery is used for power.
The load may consist of solenoids, motors, lamps, heating elements or even other electronic devices.
In figure 2 we have the assembly made on a terminal strip.
The power MOSFET can be the IRF630 or IRF640 for currents up to 5 A. The resistors are 1/8 W and the sensor consists of two coppered regions of a p´rinted circuit board of the format indicated in the figure or other. These regions should be touched simultaneously.
The drive is momentary, which means that the load remains on only during the time that the fingers are supported on the sensor.
Material list:
Q1 - IRF630 or IRF640 - any power MOSFET
R1 - 100k ohm- resistor - brown, black, yellow
R2 - 10 M ohm - resistor - brown, black, blue
X1- Sensor - see text
Miscellaneous:
Terminal strip, radiator for transistor, power supply, wires, solder, etc.
