تولید الاشارة فوق الصوتية الكترونيا .. كتاب التلفزيون الملون والعادي

19-16 Generation of the ultrasound signal electronically:

The ultrasonic signal is generated electronically, by means of an electronic oscillator and a speaker, as shown in Figure (19-22). The circuit is a Hartley oscillator 1 Q - and the primary coil of the transformer T has a connection point to regenerate the feedback from the collector to the base via the feedback capacitor C1, and the base bias is secured by the resistance 1 R connected to the negative end of the feed and connects the collector directly to the negative end of the battery (- 9 F) When any control switch is closed. It is noted that the base circuit of the oscillator and the collector is open when all switches are open. Each switch has a specific function, and it is connected with capacitors associated with the secondary files of the transformer. The capacitors are permanently connected to these files.

The frequency of the oscillator is controlled by a group of total capacitors linked through the secondary loops - and when another switch is closed, another capacitor enters the group of capacitors (3 CB-C - C) and this increases the capacitance of the capacitors and decreases the resonant frequency - and directs the signal of the pin to a capacitive speaker amplifier that spreads the ultrasonic signal .

The capacitor C2 is a chemical capacitor (electrolyte) connected to the 9V supply when the circuit is in working condition, and this prevents spoiling the circuit due to the effect of its internal resistance.

Remote Control Pistons:

If we assume that he pressed the channel change button on the controller (transmitter). Note that the pistons are normally open, and then the base and collector circuits are completed in transistor Q1, and the circuit begins to vibrate. At the same time, the two capacitors (115) connected in parallel with the secondary files of the transformer T are connected to the circuit, and this increases the capacitive resistance and decreases the frequency of the oscillator - this arrangement is very common in the circuit of the remote control device that operates with the ultrasonic wave generation system electronically, either in The receiver is a single circuit that will respond and operate. It has a resonant frequency of 43 kHz. It operates an engine that drives the channel selector from one station to another.

It is noted that there are two volume control buttons, one for volume up and the other for volume down. If the volume continues to be lowered, the device will stop working and become in the OFF state. It can be operated with a volume button. The color key works to increase or decrease the color level, Color Down Color, green color becomes dark or light green. As for the (Hue) or Tint key in some devices, it adjusts the color page in the device. When this switch is turned on, the skin color can change to a greenish or bluish red color, depending on the direction of the switch.

​The circuit of the receiver in the remote control system:

There are three or four transistors to amplify the ultrasonic signal captured by the microphone, and the amplification circuit acts as a primary amplifier, as in Figure (19-23). The signal coming from the microphone reaches 11 to Q1 through the link capacitor C1 and the method of RC circuits is usually used as a resistance - a capacitor in the connection between the phases, and the gain of 03 depends on R12 and the position of this resistance determines the sensitivity of the circuit.

Figure (19-24) shows the typical receiver - in the box diagram. The receiver has a remote control circuit. The transmitter generates ultrasonic waves, and the receiver microphone receives these signals and converts them into electrical signals that enter special amplification circuits. Then the output signal is applied to the input of tuned circuits, type LC, capacitor coil. Each circuit of it tunes to a specific frequency and does not respond to other frequencies coming from the control device, so the frequency signal

(37 kHz), for example, only the tuned resonant circuit responds to it at this frequency, so it operates the relay to carry out the function assigned to it. As for the control with a phase switch, a DC motor operates it or an electronic control circuit, and the figure shows three control circuits, while the number of circuits can be eight to ten control circuits, depending on the number of functions of the circuits required to be led.