To properly place the sensor within the existing steering column control module, one must understand the expected magnetic field that can result from the lever motion

The best location for the magnet to be installed in this test case is near the end of stalk shaft where an exposed section of the lever is exposed. The opening is approximately 12 mm × 6 mm, and a magnet of this size is easily installed as shown in Turn Indicator Magnet Location. TMAG5170-Q1 was selected as a sensor to fit into the design using the TMAG5170UEVM connected to the TI Sensor Control Board.

Figure 3-6 Turn Indicator Magnet Location

Measurements of the available mounting locations for both the magnet and TMAG5170-Q1 sensor were taken and used to simulate the expected input to the 3D Hall-effect sensor using the TI-Magnetic-Sense-Simulator.

First, with the turn-indicator lever traveling through the standard turn positions, the simulated input field components are shown in Simulated Turn Indicator Input Field, and the alignment between the sensing element and the magnet travel are depicted in Turn Indicator Magnet Motion.

Figure 3-7 Simulated Turn Indicator Input Field

Figure 3-8 Turn Indicator Magnet Motion

Simulating the magnet rotation about the Z axis (blue) shows that a spacing of 4.3 mm provides a B_z component which exceeds 150 mT, requiring that the input magnetic range for TMAG5170A2-Q1 be set the to +/-300 mT range. With this range set, a secondary simulation for the flash-to-pass lever pull were conducted to observe the minimal expected input fields when the range to the sensor is increased by the user.

Figure 3-9 Simulated Flash-to-Pass Input Field

Figure 3-10 Flash-to-Pass Magnet Motion

As a result of the additional tilt during flash-to-pass, there is a clear reduction in magnitude across all three magnetic field vector components, but there remains a large enough input signal that SNR is not a challenge.