SUPER VOLTAGE CONVERTER (ICL 7600S)

The ICL7660S performs supply voltage conversion from positive to negative for an input range of 1.5V to 12V, resulting in complementary output voltages of -1.5V to - 12V.

Figure 2 : Super Voltage Converter ICL 7660S

To run this both op-amp and voltage comparator, it need to supply the + voltage and – voltage, so this super voltage converter is the best and suitable IC (integrated controlled) to convert the input that is +12 volt from the power supply to make their own output that is -12 volt to supply for the both IC that is operational amplifier LM 741 and voltage comparator LM311.

 VOLTAGE COMPARATOR ( LM 311)

Figure 1 : Datasheet of LM 211H or LM 311H

LM311 are voltage comparators that have input currents nearly a thousand times lower. This integrated controller (IC) is single high-speed voltage comparators. These devices are designed to operate from a wide range of power supply voltages, including ±15-V supplies for operational amplifiers.

Figure 2 : Voltage Comparator LM 311

By using the circuit of interface with high level logic with voltage comparator it is to maximize the input that came from op-amp for their counter of the circuit to make either high or low output signal that will came out to as a output signal then.

CONDENSER MICROPHONE

Condenser means capacitor, an electronic component which stores energy in the form of an electrostatic field. The term condenser is actually obsolete but has stuck as the name for this type of microphone, which uses a capacitor to convert acoustical energy into electrical energy.

Condenser microphones require power from a battery or external source. The resulting audio signal is stronger signal than that from a dynamic. Condensers also tend to be more sensitive and responsive than dynamics, making them well-suited to capturing subtle nuances in a sound. They are not ideal for high-volume work, as their sensitivity makes them prone to distort.

How Condenser Microphones Work

A capacitor has two plates with a voltage between them. In the condenser mic, one of these plates is made of very light material and acts as the diaphragm. The diaphragm vibrates when struck by sound waves, changing the distance between the two plates and therefore changing the capacitance. Specifically, when the plates are closer together, capacitance increases and a charge current occurs. When the plates are further apart, capacitance decreases and a discharge current occurs.

A voltage is required across the capacitor for this to work. This voltage is supplied either by a battery in the mic or by external phantom power.

Figure 1: Overview Condenser Microphone Sensor

The Electret Condenser Microphone

The electret condenser mic uses a special type of capacitor which has a permanent voltage built in during manufacture. This is somewhat like a permanent magnet, in that it doesn't require any external power for operation. However good electret condenser mics usually include a pre-amplifier which does still require power.

Other than this difference, you can think of an electret condenser microphone as being the same as a normal condenser.

PRINCIPLES OF THE ELECTRET CONDENSER MICROPHONE

An electret condenser microphone (ECM) consists of a very light diaphragm (moving plate) and back plate (stationary or static plate) and has a permanent charge implanted in an electret material to provide polarizing voltage. The principle of operation is that sound waves impinging on the diaphragm cause the capacitance between it and the back plate to change synchronously, this in turn induces an AC voltage on the back plate.

1. Foil Electret Condenser Microphone (also called Middle or Classic) - Type of condenser microphone  where the electret material is the diaphragm. (Sometimes referred to as "Front" type.)
2. Back Electret Condenser Microphone -Type of condenser microphone where the electret material is the back plate.
3.   Front Electret Condenser Microphone -Type of condenser microphone where the electret material is the inside of the case of the microphone.

OPERATIONAL AMPLIFIER (LM 741)

Figure 1: Datasheet of LM 741

      An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An opamp produces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals.

The circuit symbol for an op-amp is shown to the right, where:

• ·         V+ : Non-inverting input
• ·         V- : Inverting input
• ·         V_out : Output
• ·         V_S+ : +12V positive power supply
• ·         V_S- : -12V negative power supply

By using non inverting circuit, this op-amp will amplified higher signal input that came from the voltage of heart beat to the circuit voltage comparator to get the output.

Figure 2: Op amp 741 with Non-inverting amplifier circuit

WORK PLAN

The time frame allocated for this project study is 12 months. It will start in July 2012 and is projected to be completed in June 2013. The Gantt chart for the project and its milestone are shown as in Table 1.

Practically, reliability is often more difficult to specify than many major performance characteristics and is certainly more difficult than most to measure. The accurate assessment of the reliability of a product in use is often difficult because of the long period needed or the large number of samples required in order to gain statistical confidence in the assessment. In reliability estimation, the failure rate models are approximations to reality. The failure rate models are normally based on the best field data that could be obtained for a wide variety of parts and systems. This data is then analysed, with many simplifying assumptions applied, to create usable models.

 Thus, one should not treat a reliability estimation numbers for the system as an absolute prediction of field failure rate. Generally, it has been agreed that these estimations can be very useful when used for relative comparison, such as comparing design alternatives, or comparing products.

Table 1 : Work Plan Schedule