HBW1631Remote Control Transmitter

THEORY OF OPERATION AND CIRCUIT DESCRIPTION MODEL 976-315LM REMOTE TOUCHCODE TRANSMITTER (Please refer to enclosed schematic drawing: 195D1631) The model 976-315LM transmitter uses a 4-digit number entered on a numeric keypad to determine the code that will be transmitted. The sequence of operation is to press 4 digits on the keypad, then press and hold the “ENTER” button (within 10 seconds of entering the last digit of the code) to operate the desired receiving device (usually a garage door opener). RF transmission begins when the “ENTER” button is pressed and continues until the button is released or 52 seconds elapses, whichever comes first. The transmitter consists of a low power RF oscillator (Q1 and related parts), a digital encoder (U1 and related parts), a voltage regulator (Q3 and related parts), and a keypad having buttons labeled “0” through “9” and “ENTER”. Operation is initiated by pressing any one of the buttons on the keypad. This turns on transistor Q4 through diodes D7, D8 or D9, which supplies current to zener diode D5. The voltage developed across D5 provides bias to the voltage regulator circuitry of Q3. The regulator applies 5V to the VCC input of U1, which causes the microprocessor to begin operation by turning on Q6, which acts to keep the voltage regulator on when the button is released. After 4 numeric buttons have been pressed, activation of the “ENTER” button will cause a digital PWM signal to appear at pin 17 of U1. This signal drives and modulates the RF oscillator. The RF oscillator is of the grounded base type. C1, C2, C11, C12, L3, and L2 set the oscillator’s center frequency to 315 MHz. C3 provides positive feedback. R2 and R3 establish DC bias conditions. In order to preserve battery life, U1 turns Q6 off when operation has ended. Turn-off occurs 20 seconds after the last RF transmission. LED's, D1-D3 and D11-D13, provide back illumination to the keypad.

USAGE CHART ROLLING CODE. LIFT MASTER001A5602 SEARS001A5602-1 REF-DESP/NDESCQTY C1 C9030D71020100CAP SMD0805 100pF 5% NPO2 C10030D710522R0CAP SMD0805 0.1uf 20% X7R1 C11030D75600000CAP SMD0805 5.6pF 5% NPO1 C1230B0444CAPACITOR, VARIABLE BOT ADJ1 C2030D73903000CAP SMD0805 3.9pF +/-.1 NPO1 C3030D71803000CAP SMD0805 1.8pF 5% NPO1 C4030D71520100CAP SMD0805 150pf 5% NPO1 C5-8030D710422R0CAP SMD0805 0.01uF 20% X7R4 D1-3 D11-1352B0074DIODE, LED T1 YELLOW6 D552B0107DIODE, SMD ZENER 5.6V1 D652B0065DIODE, SMD SIGNAL1 D7-952B0070DIODE, SMD DUAL COMMON CATHODE3 E1-2023B0099CONNECTION POINT, EXT WIRE1 L140A0104INDUCTOR, RF CHOKE 1uH SMD1 L240A0118WIRE LOOP1 L340A0136INDUCTOR, AIRWOUND 8.0nH1 N114D0632PC BOARD1 Q1207C0074TRANSISTOR, SMD NPN RF1 Q2-3 Q6207C0073TRANSISTOR, SMD NPN SWITCH3 Q4-5207C0069TRANSISTOR, SMD PNP SWITCH2 R1 R14 R31311C1025RES SMD0805 1.0K 5%3 R10-11311C2035RES SMD0805 20K 5%2 R16-17 R26-30311C4735RES SMD0805 47K 5%7 R2 R18-20311C4725RES SMD0805 4.7K 5%4 R3 R12-13 R21- 25 311C1035RES SMD0805 10K 5%8 R33311C1055RES SMD0805 1.0M 5%1 R4 R32311C4715RES SMD0805 470 5%2 R5 R7-8311C1535RES SMD0805 15K 5%3 R6 R9 R15311C1045RES SMD0805 100K 5%3 S11SWITCH, PRINTED CARBON1 S1-10 S12-13SWITCH, PRINTED CARBON12 U1125C0156SOIC, ROLLCODE KEYLESS ENTRY1 U2125C0148SOIC, ELECT. ERASABLE PROM 3V1 X133B0039RESONATOR, CERAMIC 4MHz1