Conrad Course material 3964 14 years and over 3964 Manual De Usuario
Los códigos de productos
3964
15
divert any charges. There is particular danger for the transistor if two persons touch the same circuit. Since the two
can be differently charged, a discharge via the transistor can result which destroys it.
can be differently charged, a discharge via the transistor can result which destroys it.
Fig. 39: Charging and discharging the gate (Aufbau14.jpg)
16.
Step: Sensor-dimmer
With an additional capacitor between gate and drain, intermediate states between “completely on” and “completely off”
are also preserved. If the voltage at the gate drops, the drain current becomes smaller and the voltage also drops at
the LED and its series resistor. The drain voltage therefore increases. This is only possible if the capacitor is charged.
Every change in the drain voltage counteracts a change in the gate voltage. Thus, with a small input current the LED
brightness only changes slowly. If the contacts A and B touch, the LED gets brighter. By contrast, to make it darker C
and D must touch. The time it takes for a reaction to touching differs in the two cases. Brightening takes place more
quickly than darkening due to the higher charging voltage.
are also preserved. If the voltage at the gate drops, the drain current becomes smaller and the voltage also drops at
the LED and its series resistor. The drain voltage therefore increases. This is only possible if the capacitor is charged.
Every change in the drain voltage counteracts a change in the gate voltage. Thus, with a small input current the LED
brightness only changes slowly. If the contacts A and B touch, the LED gets brighter. By contrast, to make it darker C
and D must touch. The time it takes for a reaction to touching differs in the two cases. Brightening takes place more
quickly than darkening due to the higher charging voltage.
Fig. 40: The touch dimmer (Schaltung15.jpg)
Fig. 41: Adjustable brightness (Aufbau15.jpg)
17.
Step: Electrometer
An electrometer is a measuring device for detection of small electric charges. Electrically charged objects or persons
carry an electric field with them which can charge insulated objects in the surrounding area through electrostatic
induction. This also applies to the insulated gate of the BS170. An insulated wire is connected at the input of the
circuit. Electric charges in the surrounding area then influence the LED brightness. You can, e.g., rub a plastic ruler on
a cloth and hold it near the circuit. In doing so, maintain a safety distance of 10 cm so as to not damage the MOSFET.
carry an electric field with them which can charge insulated objects in the surrounding area through electrostatic
induction. This also applies to the insulated gate of the BS170. An insulated wire is connected at the input of the
circuit. Electric charges in the surrounding area then influence the LED brightness. You can, e.g., rub a plastic ruler on
a cloth and hold it near the circuit. In doing so, maintain a safety distance of 10 cm so as to not damage the MOSFET.