MINI MICROPHONE PRE-AMPLIFIER USING LM358

This is easy to construct microphone pre-amplifier project using compact electret condenser microphone. The pre-amplifier is important building block of many audio communication systems. Circuit has been built around Op-Amp LM358.

 

  •  Power supply : 5 to 12 VDC @ 10 mA
  •  Output: Gain Approx. 100
  •  On-Board electret condenser microphone 
  •  Header connector for connecting of power supply input and audio output
  •  Power-On LED indicator

 

 

 

 

 

 

Quadrature Encoder to Clock and Direction Signal Converter Using LS7084/LS7184

The quadrature LS7084/LS7184 Module is a CMOS quadrature clock converter. Quadrature clocks derived from optical or magnetic encoders, when applied to the A and B inputs of the LS7084 are converted to strings of a Clock and an Up/down direction control. These outputs can be interfaced directly with standard Up/Down counters for direction and position sensing of the encoder.

J1 Jumper input selects between x1 and x4 modes of operation. A high level selects x4 mode and a low-level selects the x1 mode. In x4 mode, an output pulse is generated for every transition at either A or B input. In x1 mode, an output pulse is generated in one combined A/B input cycle.

Resistor R7-RBIAS (Pin 1) Input for external component connection. A resistor connected between this input and VSS adjusts the output clock pulse width (Tow). For proper operation, the output clock pulse width must be less than or equal to the A, B pulse separation (TOW £ TPS).

 

Features

  • Supply 5V DC
  • +4.5V to +10V operation (VDD – VSS)
  • On Board Power LED
  • J1 Encoder pulse multiplication ( Jumper JL Close =1X, Jumper JH Close = X4)
  • Header Connector for Encoder Interface
  • X1 and X4 mode selection
  • Programmable output clock pulse width
  • On-chip filtering of inputs for optical or magnetic encoder applications.
  • TTL and CMOS compatible I/Os
  • Up to 16MHz output clock frequency

 

Note : Circuit uses LS7084 IC , which is CMOS IC and working voltage range 4.5V to 10V and it has two scale up  range.X1 and X4. The board can be used with LS7184 which can work with lower supply range 3.3V to 5V and it can provide X1,X2,X4 resolution, refer data sheet of LS7184 for more information.

 

 

 

 

 

 

 

Note: Check Graph for R7- Bias Selection

 

 

 

 

What is Quadrature Encoder?

The most common type of incremental encoder uses two output channels (A and B) to sense position. Using two code tracks with sectors positioned 90 degrees out of phase, the two output channels of the quadrature encoder indicate both position and direction of rotation. If A leads B, for example, the disk is rotating in a clockwise direction. If B leads A, then the disk is rotating in a counter-clockwise direction.

By monitoring both the number of pulses and the relative phase of signals A and B, you can track both the position and direction of rotation.

Some quadrature encoders also include a third output channel, called a zero or index or reference signal, which supplies a single pulse per revolution. This single pulse is used for precise determination of a reference position.

How Quadrature Encoder Works?

The code disk inside a quadrature encoder contains two tracks usually denoted Channel A and Channel B. These tracks or channels are coded ninety electrical degrees out of phase, as indicated in the image below, and this is the key design element that will provide the quadrature encoder its functionality. In applications where direction sensing is required, a controller can determine direction of movement based on the phase relationship between Channels A and B. As illustrated in the figure below, when the quadrature encoder is rotating in a clockwise direction its signal will show Channel A leading Channel B, and the reverse will happen when the quadrature encoder rotates counterclockwise.

Apart from direction, position can also be monitored with a quadrature encoder by producing another signal known as the “marker”, “index” or “Z channel”. This Z signal, produced once per complete revolution of the quadrature encoder, is often used to locate a specific position during a 360° revolution.

Constant Current Laser Diode Driver Using OPA2350 OP-AMP

The voltage-controlled current source circuit can be used to drive a constant current into a signal or pump laser diode. This simple linear driver provides a cleaner drive current into a laser diode than switching PWM drivers. The basic circuit is that of a Howland current pump with a current booster (Q1) on the output of a R-R CMOS OPA2350 op amp (U1). Laser diode current is sensed by differentially measuring the voltage drop across a shunt resistor (RSHUNT) in series with the laser diode. The output current is controlled by the input voltage (VIN) that comes from Trim pot PR1.

Features,

  • Supply 3,3V DC
  • Load Up to 300mA
  • PR1 Trimpot Current Adjust

 

 

Download Data Sheet OPA2350

 

 

 

4 Channels Optically Isolated I/O Board Using 6N137 Optocoupler

4 Channel Opto isolated board has been designed around 6N137 Opto-coupler, the 6N137 optocoupler is designed for use in high-speed digital interfacing applications that require high-voltage isolation between the input and output. Applications include line receivers, microprocessors or computer interface, digital programming of floating power supplies, motors, and other control systems.

The 6N137 high-speed optocoupler consists of a GaAsP light-emitting diode and an integrated light detector composed of a photodiode, a high-gain amplifier, and a Schottky-clamped open-collector output transistor. An input diode forward current of 5 milliamperes will switch the output transistor low, providing an on-state drive current of 13 milliamperes (eight 1.6-milliampere TTL loads).

Note : For 3.3 Input Signal R1, R4, R7, R10 = 220E

Features

  • Supply 5V DC
  • Input Signal : 5V DC TTL
  • Header Connectors for Inputs & Outputs
  • D1 Power LED