To go from 45° to 90° requires two HMC1501 sensors or a single HMC1512 dual sensor part. By using two bridges with 45° displacement from each other, the two linear slopes can be used additively. Figure 8 shows a typical configuration. From Figure 8, as the shaft rotates around, magnetic flux from a magnet placed at the end of the shaft exits the north pole and returns to the south pole. With a HMC1512 placed on the shaft axis, just above the magnet, the flux passing through the sensor bridges will retain the orientation of the magnet. From this rotation, the output of the two bridges will create sine and cosine waveforms as shown in Figure 9.

Because the sine (sensor bridge A) and cosine (sensor bridge B) will match after the offset error
voltages are subtracted, the ratio of bridge A to bridge B creates a tangent 2O function and the amplitude A values cancel. Thus the angle theta is described as:

However because there are some trigonometric nuances with the arctangent function when gets close to _45° and beyond, these special cases apply:

Because most trigonometric functions are performed as memory maps in microcontroller integrated circuits, these kinds of special case conditions are easily dealt with. The resultant angle theta is the relative position of the magnetic field with respect to the sensor. It should be noted that if rotation is permitted beyond _90°, the theta calculation will replicate again with postive and negative 90° readings jumping at the end points. Further performance to 360° or _180° can be mapped into a microcontroller by using this circuit plus a Hall Effect sensor to determine which side of the shaft is being positionally measured via magnetic polarity detection. Figure 10 shows the basic circuit interface for the HMC1512.

HMC1501 / HMC1512
Linear / Angular / Rotary
Displacement Sensors
High resolution, low power MR sensor capable of measuring the angle
direction of a magnetic field from a magnet with <0.07>

HMC1501 Datasheet pdf

Technorati Tags: WIDER POSITION SENSING CIRCUIT

Bidirectional Hall Effect Based Linear Current Sensor with
Voltage Isolation and 20 A Dynamic Range


ACS706ELC-20A
The Allegro ACS706 family of current sensors provides economical
And precise solutions for current sensing in industrial, automotive,
commercial, and communications systems. The device package allows
for easy implementation by the customer. Typical applications include
motor control, load detection and management, switched-mode power
supplies, and overcurrent fault protection.
Current Input Range Min -20 A Max 20 A
Output Voltage versus Current Input (Vcc = 5V)

Features
• Small footprint, low-profile SOIC8 package
• 1.5 mΩ internal conductor resistance
• Excellent replacement for sense resistors
• 1600 VRMS minimum isolation voltage between pins 1-4 and 5-8
• 4.5 to 5.5 V, single supply operation
• 50 kHz bandwidth
• 100 mV/A output sensitivity and 20 A dynamic range
• Output voltage proportional to ac and dc currents
• Factory-trimmed for accuracy
• Extremely stable output offset voltage
• Near-zero magnetic hysteresis
• Ratiometric output from supply voltage

ACS706ELC-20A Datasheet pdf


Technorati Tags: Bidirectional Current Sensor

The AD202 are general purpose, two-port,transformer-coupled isolation amplifiers
In applications where the output ofthermocouples must be isolated, a low drift input amplifier can be used with an AD204,as shown in Picture.

A three-pole active filter is included in the design toget normal-mode rejection of frequencies above a few Hz and to provide enhanced common-mode rejection at 60 Hz.
If offset adjustment is needed, it is best done at the trim pins of the OP07 itself; gain adjustment can be done at the feedback resistor. Note that the isolated supply current is large enough to Mandate the use of 1 mF supply bypass capacitors.

This circuit from AD202 Application

Technorati Tags: Isolated Thermocouple Transducer Circuit

AS5145
12-Bit Programmable Magnetic Rotary Encoder
The AS5145 is a contact less magnetic rotary encoder for accurate angular measurement over a full turn of 360 degrees. It is a system-on-chip, combining integrated Hall elements,analog front end and digital signal processing in a single device. To measure the angle, only a simple two-pole magnet, rotating over the center of the chip, is required. The magnet may be placed above or below the IC.The absolute angle measurement provides instant indication of the magnet’s angular position with a resolution of 0.0879º = 4096 positions per revolution. This digital data is available as a serial bit stream and as a PWM signal.An internal voltage regulator allows the AS5145 to
operate at either 3.3V or 5V supplies.

Typical magnet (6x3mm) and magnetic field distribution

Daisy Chain Mode
The Daisy Chain mode allows connection of several AS5145’s in series, while still keeping just one digital input for data transfer (see “Data IN” in Figure 9). This mode is accomplished by connecting the data output (DO; pin 9) to the data input (PDIO; pin 8) of the subsequent device. The serial data of all connected devices is read from the DO pin of the first device in the chain. The length of the serial bit stream increases with every connected device, it is n * (18+1) bits: n= number of devices. e.g. 38 bit for two devices, 57 bit for three devices, etcetc.

AS5145 Datasheet

Technorati Tags: Magnetic Rotary Encoder to Microcontroller Circuit

This circuit used convert signal from Rotary encoder (A,B) to two pulse signal
- Y for CCW direction
- X for CW (clockwise) direction
Two pulse signal is easy for microcontroller programing
The circuit used two D-type flip-flop(74HC74D) for the judgement.

Signal input and signal out put

Technorati Tags: Rotary encoder converter circuit