Power amplifier electronic circuits-tube audio rf amplifiers

Circuit Description

The circuit diagram of window foil burglar alarm has been published here. The main parts of this circuit are SCR H1 (TYN 612) and transistor Q1 (BC 107). This burglar alarm can be fitted in windows to check breaking attempts.

Here the sensing element of break attempt is a network of fine wire element fitted through the window glass. At normal condition, the transistor Q1 will be in off state since its base is connected to the ground. Then SCR will be in non-conducting state since it has not been triggered. When a break attempt of window comes, then the wire elements will break and the base of transistor will connect to positive potential. This turns on Q1 and the output of it triggers SCR.  This turn on of SCR turn horn to blow and the circuit remains on unless power supply is switched off.

Circuit Diagram

Window Foil Burglar Alarm Circuit

Notes

• To setup the circuit, make switch S1 open and adjust R2 to get a 1V between base of Q1 and ground. Now transistor will be conducting and horn will be blowing.
• Now, close S1 and reset the power supply .The transistor Q1 will be off and horn will not be blowing. Then circuit is ready.
• Make a loop of very fine wire through the window glass to make the window foil (two or three lines running in both direction is enough).

Circuit Description

The circuit diagram of tweeter crossover circuit has been described here. The advantage of this circuit over circuits of single coil speaker is that it can handle both high and low frequency signals simultaneously. A tweeter circuit can produce a better sound clarity than single speaker circuit if low frequency is filtered out from the amplifier output.  That principle is applied in this particular circuit. Here a low pass filter circuit consisting of elements C1, C2 (25 uF) and potentiometer R1 (100 ohm) is used for filtering high frequencies. This filtered output is given to the tweeter (K2). The existing woofer (K1) is driven with the low frequency.

Circuit Diagram

Simple Tweeter Crossover Circuit

Notes

• The power rating of potentiometer should not be less than 2 Watts.
• Use electrolytic capacitors for C1 and C2.
• The tweeter can be a 2 to 3 inch, 4 to 8 Ohm one.
• Potentiometer R1 is used to adjust the output level of tweeter to that of woofer to match both.

Circuit Description

Here is the circuit diagram of remote controlled appliance switch circuit. The main parts of this circuit are IC1 (NE 555), IC2 (CD 4017), IC3 (TSOP 1738), Q1 (BC 158) and Q2 (SL 100). This device can switch on/off any appliance connected to it using a TV remote.

Here the IR remote sensor is TSOP 1738 whose output is high when no signal is falling on it and becomes high if 38 KHz signal from TV remote falls on it. When the output of IR sensor becomes low, that will turn transistor Q1 into conducting state. Its low output triggers IC1 which is wired as monostable multivibrator and it produces 4 sec long high signals at its out put. This signal is given as clock to IC2 which is a flip-flop having two output pins (2 and 3). Then pin3 goes low and pin2 goes high. The output of pin2 is used to drive the relay through transistor Q2. The output of IC2 toggles when the next signal comes. As a result of this on each press of remote, the relay will be toggled and hence the appliances connected to it can be switched on/off by remote.

Circuit Diagram

Remote Control Appliance Switch Circuit

Notes

• Use a good quality PCB or common board to assemble this circuit.
• Use TV remote having a frequency of 38 KHz.
• The appliance can be connected through NO or NC and C contacts of the relay.
• Use a 6 V DC regulated supply for powering this circuit.