Remote control curtain circuit b

The remote control electric curtain introduced below can effectively control the opening and closing of the curtain within a distance of 3-5m from the window, which not only facilitates the owner but also
adds modern flavor to the home. This kind of remote control electric curtain is divided into two parts: the transmitter and the receiver. Its circuit is simple, the materials are convenient, and it
is easy to make and debug.
    (1) Working principle of the transmitter circuit The transmitter of the remote control electric curtain is shown in Figure 18-33a. The transistors VTI and VT2 together form an inductive
three-point push-pull oscillator. The supports and islands in the circuit are bias resistors, and G and c{ are feedback capacitors. Cl and L. By forming a parallel resonant circuit and adjusting
the capacity of C, the oscillation frequency of the transmitter can be tuned, and the oscillation frequency is approximately 28-30MHz. Lz is the antenna coupling line, which can
couple the high-frequency constant-amplitude oscillation in Li and emit it from the antenna to the surrounding space.
  Selection of components: VT1 and VT2 are any type of NPN low-power silicon tubes. There are many models available, such as 3DG6C,
3DG8C; 3DK3, etc. It is required that the p of the two tubes is >80, and the Lu values ​​of the two tubes are similar. The operating frequency of these two transistors is relatively high. An important parameter to measure the operating frequency of the transistor is the characteristic frequency jT. Its definition is: as the operating frequency increases, the output value of the transistor decreases. fT is the operation when
J9 decreases to 1.
Frequency, here requires fr > 200MHz of the two tubes. Ci is a semi-variable porcelain dielectric capacitor of 5/20pF; G and cI are
mica or porcelain dielectric capacitors of 50 to 100pF; the resistance values ​​of Shu and Dao are determined during adjustment, and the resistance values ​​are 15 to 50kfl. :
    h Use silver-plated wire or enameled wire with a diameter of L Omm to be wound around a round rod with a diameter of 12 mm. After winding, weld a tap with a wire at 6 turns
. Then pull out the round rod and stretch the coil to 2.5mm long to make a hollow bodied coil.
  L uses diameter o. Wrap 9mm silver-plated wire or Taobao wire 4 times around a round rod with a diameter of 9mm, pull out: the round rod is then stretched to 7mm. When using for welding
, install L2 inside.
    The voltage of power supply E can be selected between 9-15V. The higher the voltage, the greater the transmit power. In order to reduce the size of the transmitter,
a laminated battery is used here .
    (2) Working principle of the circuit of receiving and mechanical parts
    : The circuit of the receiving part is shown in Figure 18-33b. It consists of a remote control receiving circuit and a bistable circuit. The principle of remote
control reception is very simple. The signal emitted by the transmitter received by the antenna is coupled to the resonant circuit composed of L3 and C5 through capacitor C6,
and then the signal is sent to the diode for detection, and then passes through C7, b, L; After filtering, it is sent to the amplifier composed of VT3, VT4 and VT5 for amplification.
K in the circuit is the reed switch coil . When no signal is received. The output current of VT5 is very small, and the magnetic field generated in LcJ cannot attract the reed switch.
When receiving the signal command from the transmitter, the collector current of VT5 surges, which greatly enhances the magnetic field in the reed switch coil. The reed switch
is closed.
    The bistable circuit is composed of transistors VT6 and VT7. When the power is turned on, one of VT6 and VT7 must be cut off and the other saturated, which is
determined by its circuit structure. Assume that VT6 is in the cut-off state, that is to say, the collector potential of VT6 is approximately equal to the power supply voltage. This voltage
is added to the base of VT7 through the divided voltage of R8 and the island. If the circuit parameters are properly selected, vr7 can obtain a large enough base current
, thus making VT7 work in a saturated conduction state. Because VT7 is in a saturated state, the collector potential of VT7 is close to zero, and
the collector voltage of VT7 is added to the base of rr6 through the Rz island. Since VT6 and VT7 have resistors Rr on their emitters, ,． As long as
the resistance values ​​of Riz and Horse are appropriate, the base potential of VT6 can be lower than the emitter potential, thus ensuring that VT6 is in a stable cut-off state. If
the working conditions of the circuit are not changed, the circuit will always be in this stable state (VT6 is turned off and VT7 is turned on). It can be seen that in a bistable
circuit, the cut-off of one tube ensures the saturated conduction of the other tube, and the saturated conduction of the other tube ensures the cut-off of this tube. The cut-off
or saturated state of the two tubes Alternate and restrict each other.
    Assume that a negative pulse signal with sufficient amplitude is added to the base of saturated conduction tube VT7 (that is, a negative input signal with a short
acting ), so the base potential of VT7 decreases. , the base current decreases, and if it decreases to a certain extent, it will cause VT7
to exit the saturation state - its collector potential increases. Since the collector voltage of VT7 passes through R. : and R, the partial voltage is added to the base of VT6, causing
the base potential of the cut-off tube VT6 to rise and exit the cut-off state. At this time, even if the negative pulse applied to the base of VT7 no longer exists (because its action time is very short), because the collector potential of VT6 has decreased, the transistor has entered the amplification zone to work, and through the voltage
division of Ra and R9
Coupling will also further reduce the base potential of VT7, making its collector current smaller. In this way, the
chain reaction is carried out one after another. The base potential of VT7 is getting lower and lower, and the base potential of VT6 is getting higher and higher.
This . So the t bistable circuit stabilizes in this new state (VT7 is cut off, VT6 is saturated and turned on). Under the action of an external signal
, the process of a bistable circuit from one stable state to another stable state is called flipping. If another negative pulse is added to the base of VT6 at this time
, the circuit will repeat the above process and round out the state where VT7 is saturated and VT6 is cut off.
    C8 in the circuit is charged with a very high voltage (approximately equal to the power supply voltage). When the receiving circuit receives the signal from the transmitter, the reed switch is
attracted, and the negative electrode of cs is connected to G and Cl. Turning on, this is equivalent to adding a negative pulse to the bases of YF6 and VT7 at the same time. Since the negative pulse only
works on the saturated transistor, the bistable circuit flips over at this time and enters a new stable state. . When the transmitter sends a signal again and the reed switch closes again
, the circuit is triggered back to its original state. The relay K connected in series to the collector circuit of VT7 also acts in conjunction with the bistable circuit. When
the relay is closed, the transmitter sends a signal to release the relay. When it is transmitted again, the relay fork is closed again.
    The motor control circuit is shown in Figure 18-3 3c. Circle -K2 is the contact of the relay in the receiving circuit , and Sl and s2 are self-made limit switches. When
the relay is closed, the middle reeds of Kl and K2 are connected to the normally open contacts, and the power is supplied to the motor through Sl and S2. The motor rotates and the scale
For forward rotation. Start pulling the curtain; when the curtain is closed, the stopper set on the pull wire disconnects S2. At this time, the motor lip is powered off and stops moving. : If you
want to open the curtains, you can send the remote control signal again to release the relay. It can be seen from Figure 18-33 that the center reeds of Kl and K2 are connected to the normally closed contacts
, the motor reverses due to the reverse connection of the power supply, and the curtains are opened. When it is pulled to a certain position, another stopper on the pull wire turns
off the limit switch Sl, and the motor stops due to the disconnection of the power supply: