Infra-Red Wireless Remote Control
Operation of Receiver
- The receiver consists of a PIN photo diode, amplifier, LC tuning circuit, detection circuit, and wave-form shaping circuit (Schmitt Trigger), and it changes the infrared signal from the transmitter into the original 10-bit signal.
- The 10-bit pulse signal is processed by the microcomputer, and then the necessary remote control signal is taken out from each output port.
- The output interface is a circuit to facilitate the conection with each equipment, and it is an inverter using an open collector.
Operation of Transmitter
- MN6025C is an 5-bit IC which can generate 25 kinds of signals. The oscillation frequency is 396 kHz and is divided by 12 to obtain 33 kHz which is used as modulation frequency. It is further divided by 16 to achieve 2,06 kHz which is the clock frequency of this IC.
- When the keyboard is depressed, Mn6025C starts oscillating and generates series pulses of 5 bits plus inverse 5 bits, totalling 10 bits, according to the key position.
- The 10-bit pulse signal is modulated by 33 kHz carrier.
- The modulated signal from MN6025C is applied to the infrared LED and command eye LED drive circuits. With oscillation time is about 60 msec. required for 10 bits, while the lighting up time of the command eye is set at about 0,5 sec.
Electronic Volume Control
- In this control, five attenuators of -2 dB, -4 dB, -8 dB, -16 dB and -32 dB, and a muting circuit of -20 dB are turned On-Off by an analog switch for changeover in 32 steps renging from 0 dB to -6 dB and to ∞ by -2 dB each.
- The analog switch is driven by a 5-bit binary up-down counter, which is provided with last sound function due to the back-up signal from the tuner pre-amplifier.
- The volume control up-down switch gains 1 step in the initial 0,5 sec. of push, and keeping it depressed causes step-by-step volume control every 0,15 sec. When the switch is kept depressed, it takes about 5 secondes for the change from 0 dB to -∞ dB.
- A 5-bit IC (LC7500) is used as the controller for the electronic volume. With this IC, the five attenuators can be selected in 32 steps. The internal oscillation frequency 800 Hz is divided into pulses of 0,15 sec. period, and the pulses are counted at the counter circuit to select the attenuators.
When the volume up-down switch is pressed, three pulses are first
counted to select an attenuator and subsequently the attenuators are selected
every pulse.
Specifications
Receiver
Unit
Input
Sensitivity / Impedance: 500 mV/27 k Ω
Maximum
Allowable Input: 11 V
Total
Harmonic Distortion: 0,015% (at rated
output)
Signal-to-Noise
Ratio:
At Rated
Output : 90 dB (92 dB, IHF, A)
At -26 dB
Output : 68 dB
Frequency
Response: 20 Hz - 20 kHz , +0 dB, -0,5
dB
Residual Hum
and Noise: 0,03 mV
Volume
Control Range: 0 dB to -60 dB (2 dB
steps), -∞ in 32 steps
Muting: -20 dB
Output
Voltage [Rated/Maximum]: 500 mV / 3 V
Output
Impedance: 2,2 k Ω
Channel
Balance: 250 Hz to 6,300 Hz , ±1,0 dB
Chnnel
Separation (1 kHz): 65 dB
Power
Consumption: 6 W
Power
Supply: 110, 120, 220, 240 V AC 50/60 Hz
Dimensions
(W x H x D): 430 x 75 x 270 mm
Weight: 3,7 kg
Transmitter
Unit
Effective
Signal-Transmission Distance: Approx. 7
m
Power
Supply: DC 3 V (two 1,5 V batteries)
Dimensions
(W x H x D): 63 x 22 x 142 mm
Weight: 136 g (with batteries)