The Hall effect refers to the measurable voltage present when an applied current is influenced by a perpendicular magnetic field. When the vehicle operator moves the lever, the magnet is moved past the individual Hall devices. The top panel displays switching to logic low in the presence of a strong south polarity field, and the bottom panel displays switching to logic high, also in a south polarity field. A very strong field will not damage an Allegro Hall-effect device nor will such a field add additional switchpoint hysteresis other than the designed hysteresis. There are four general categories of Hall-effect IC devices that provide a digital output:
|Date Added:||20 August 2005|
|File Size:||56.10 Mb|
|Operating Systems:||Windows NT/2000/XP/2003/2003/7/8/10 MacOS 10/X|
|Price:||Free* [*Free Regsitration Required]|
Basically, this means that uni;olar to this elapsed time after providing power, device output may not be in the correct state, but after this time has elapsed, device output is guaranteed to be in the correct state. When the field is more positive than B OPthe device turns on. Caution however is required because large pull-up values make it possible to induce external leakage currents to ground.
Unipolar switch output characteristics. When the magnetic field again drops below B RPthe device turns off. Most new device designs utilize a chopped Hall element. An application for detecting the position of a vehicle gear-shift lever is shown in figure 1.
Unipolar Hall-Effect Sensor IC Basics
Note that the south pole of the magnet colored red is toward the Hall devices, and that the Hall devices are oriented with the branded face of the device toward the magnet south pole. Digital output devices, such as the unipolar switch, reach stability with the following approximate delays: Power-on time depends to some extent on the device design.
After it has been turned-on, the unipolar IC will remain turned-on until the magnetic field is removed and the IC reverts to its off state.
When a unipolar switch turns on, the resulting output signal can be either at logic high or logic low, depending on the design of the device IC output stage.
Power-On Time Power-on time depends to some extent on the device design. Following the arrows back toward the left, the magnetic field becomes less positive.
Digital output devices, such as the unipolar switch, reach stability with the following approximate delays:. For example, for the “UA” package, the chip with the Hall element is 0.
Allegro MicroSystems – Unipolar Hall-Effect Sensor IC Basics
The branded face is where you will find the identification markings of the device, such as partial part number or date code. The devices near the magnet are subjected to the magnetic field and are turned-on, but more remote devices are not affected and remain turned-off. This may also allow higher operational temperatures. The distance from the branded face to the Hall element is referred to as the “active area depth.
This convention allows arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of B, and the sign indicates the polarity of the field. When the vehicle operator moves the lever, the magnet is moved past the individual Hall devices.
The minimum pull-up resistance is a function of the Hall IC maximum output current the devices usually are designed to sink current and the supply voltage. Take this unipolaar to the derating chart in the datasheet for the package in question and check to see if the maximum allowable operational temperature must be reduced. This is not a device problem, rather the leakage occurs in the conductors between the pull-up resistor and the device output pin.
The transfer function of a Hall device is designed with this offset between the switchpoints to filter out small fluctuations in the magnetic field that can result from mechanical vibration or electromagnetic noise in the application. Following the arrows toward the right, the magnetic field becomes increasingly positive.
The Hall effect refers to the measurable voltage present when an applied current is influenced by a perpendicular magnetic field. The top panel displays switching to logic low in the presence of a strong south polarity field, and the bottom panel displays switching to logic high, also in a south polarity field. The line of miniature black boxes is an array of unipolar switch devices. The following are terms used to define the transition points, or switchpointsof Hall switch operation:.
The gear-shift lever incorporates a magnet the red-and-blue cylinder.
This causes the output voltage to change to the opposite state either to high or to low, depending on the device design. Typical Operation When a unipolar switch turns on, the resulting aallegro signal can be either at logic high or logic low, depending on the design of the device IC output stage. Unipolar Hall-effect sensor ICs, often referred to as “unipolar switches,” are operated sllegro a positive magnetic field.
Taken to the extreme, this can reduce the output voltage enough to inhibit proper external logic functions.