Building a Microphone Amplifier - Watch Timing System Building a Microphone Amplifier The microphone used in the produces a very weak signal, generally on the order of 10µV, whereas a sound card is expecting a signal of about 500mV to 1V at the Line In jack, or 50-100mV at the Microphone jack. The amplifier boosts the signal level up to 6000-fold, and also helps to reject background noise. Building the amplifier requires some electronic construction experience. The Circuit The amplifier consists of three stages, each using one operational amplifier (op-amp) of a TL074 quad low-noise op-amp IC.

Each stage consists of a passive high pass filter, followed by an amplifying active low-pass filter. An additional high pass filter follows the last stage, and together, the high pass filters greatly attenuate 50Hz or 60Hz AC (mains) hum. The active low pass filters, with a cut-off frequency of about 11kHz, reduce high frequency background noise.

Feb 21, 2018 It does not come with any software. Timetrax Model 20 clip on sensor, 1 pc output cable with BNC connector for use with an instrument recorder. MicroSet Model 2 adds two unprecedented new functions in a clock timing tool. Built-in beat amplifier (optional). Computer interface software.

The schematic and circuit board layout are shown below (click image for a high resolution PDF version): The fourth op-amp in the TL074 provides a stable 'virtual ground' at about 40% of the supply voltage. This allows the entire circuit to operate from a single-polarity 9V power source (a 9V battery).

A piezo-electric transducer like the one used as a microphone in this project has a very high DC impedance and acts in a circuit like a very low-valued capacitor, on the order of 20 to 30nF. Normally, when designing a piezo amplifier for audio applications, one wants a very high input impedance in order to obtain sufficient bass response. For a watch microphone however, low frequencies should be rejected. By using a fairly low input impedance (33kΩ), the piezo transducer itself becomes part of the first high pass filter stage. F1 2002 Mod 2008 Download. Parts and Materials The amplifier can be constructed on a printed circuit board, or any other circuit fabrication technique you are comfortable with (an earlier prototype, for example, was constructed on stripboard). The remainder of this article assumes the use of a printed circuit board.

To aid in rejection of 50Hz or 60Hz AC hum, the amplifier should be enclosed in a metal case, electrically connected to the circuit's ground. Shielded audio cable must be used for all connections to the amplifier.

• measures the beat time of clock and watches (Average 1 to 254 ticks, default value for beat count can be programmed) • Display results in Seconds Per Beat or Beats Per Hour • Acoustic sensor to measure from the tick sound• Automatically disregard extraneous sounds at improper intervals (A 'blanking window' makes the timer 'deaf' between ticks) • Optical sensor to measure from the pendulum swing on clocks with pendulums. The optical detector gives more accurate readings and ignores noises like chimes and hourly strike.• Special mode for reading Atmos clocks (Rate is displayed as 30.000000 Seconds Per Beat) • Special mode for finding the rate of unknown movements by measuring the minute hand • measures the ratio between even and odd ticks to put a clock or watch 'in beat'. • determines the correct beat time of any running pendulum clock without train tables or counting teeth.