Sunday, April 15, 2012
LM 3915 Sound Level Meter Circuit
This is a one chip sound level meter that can be use for displaying sound level of an amplifier or simply the sound level from a microphone.The heart of the circuit is IC LM 3915 Audio level IC.Even though it is a stand alone IC , a peak detector based on Transistor BC 558 and diode 1N4001 is also included for better performance.Supply voltage can be from 3V to 20V.The input is set for audio line voltage (1V peak to peak) and has a max input voltage of 1.3V. To make the circuit use a moving dot display instead of bar graph display,Pin 9 can be should be disconnected from +V.
Part List
C1 2.2uF 25V Electrolytic Capacitor
C2, C3 0.1uF Ceramic Disc Capacitor
R1, R3 1K 1/4W Resistor
R2 10K 1/4W Resistor
R4 100K 1/4W Resistor
R5 1M 1/4W Resistor
D1 1N4001 Silicon Diode
Q1 BC 558 PNP Transistor
LED1-LED10 Standard LED or LED Array
U1 LM3915 Audio Level IC
MISC Board, Wire, Socket For U1
Sunday, April 1, 2012
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Saturday, March 31, 2012
6Volt Doorbell Light Circuit
This 6V battery operated doorbell light circuit can be affiliated in alongside with any absolute AC230V doorbell. When anyone advance the doorbell switch, the alarm sounds as accepted and ac mains accumulation accessible beyond the doorbell is baffled to the ascribe of this ambit through an opto-coupler(IC1). Conduction of IC1 triggers a monostable, active about the acceptable old 555 timer (IC2). As a aftereffect the high-bright white LED (D2) at the achievement of IC2 is switched on for a abbreviate time. This ambit is awful advantageous at night/midnight as it gives acceptable calm ablaze to advice you locate switches for allowance lamp/porch light, etc. On/Off continuance of the LED ablaze can be increased/decreased by increasing/decreasing the amount of C2.
The electronic doorbell circuit is absolutely safe because it is altogether abandoned from the baleful ac mains accumulation by IC1. However, accumulate to abstain adventitious contacts with the foreground end of the circuit, which is anon affiliated to the ac supply. Use of a acceptable and acceptable ABS asylum is recommended for this doorbell ablaze unit.
Wednesday, March 21, 2012
Cable TV amplifier With 2 Transistors
This is a actual simple cable TV amplifier application two transistors. This amplifier ambit is a lot of acceptable for cable TV systems application 75 Ohm coaxial cables and works accomplished up to 150MHz. Transistor T1 performs the job of amplification. Up to 20dB accretion can be accepted from the circuit.T2 is active as an emitter addict to access accepted gain.Notes.
- The circuit can be assembled on a Vero board.
- Use 12V DC for powering the circuit.
- Type no of the transistors are not very critical.
- Any medium power NPN RF transistors can be used in place of T1 and T2.
- This is just an elementary circuit. Do not compare it with high quality Cable TV amplifiers available in the market.
