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7. Appendix 1 - Inductive Position Sensor Calibration
The Bullseye board features the Renesas ZMID4200 inductive position sensor, which is configured to
provide a proportional voltage output relative to the actuator position (between 0 to 2 inches), and the
output voltage range is set at 5% to 50% of the ZMID4200 supply voltage (~5V) to comply with the ADC
input requiremments (~2.5Vmax). The OOB demo firmware default setting assumes the ZMID4200 supply
is at 5.1V for the voltage-to-position conversion. When powering the Bullseye board via J5 micro USB
port, instead of J1, due to the ORing diode in series, the sensor supply voltage may become as low as 4.6V
instead of 5.1V. In order to get a more accurate position sensing, the OOB demo software provides an
easy way to compensate different supply level by performing the following simple calibration process.
Inductive position sensor calibration:
•
Press once the User Button (S2) on the Bullseye board to start the position calibration process
Green LED will start blinking 2 times/sec to indicate "0 inch" position calibration step.
•
Place the Actuator board on the "0 inch" position between the guide rails (Leftmost position) by
lining-up the arrows on the Actuator board with the corresponding top and bottom arrow tips on the
outside of the two guide rails.
•
Press again the User Button (S2) once to capture the current voltage for the "0 inch" position
Green LED will turn off
The Red LED will start blinking 2 times/sec to indicate "End position (2 inches)" calibration step.
•
Place the Actuator board at the "2 inches" position (Rightmost position) with the same arrows
lining up procedure
•
Press once the Button (S2) again to capture the current voltage for the "2 inches" position
Red LED will turn off. The calibration process is completed.
Notes: These calibration values are not saved in non-volatile memory. After a reset or changing
power source input, repeating the calibration process is needed to get accurate position
output.
For developers, another option is to measure the +5V_SYS rail with an ADC input to
automatically adjust the equation. ex: using the mikroBUS interface, connect a resistor divider
(÷2) between the +5V pin, GND pin and to the AN pin (max~2.5V). Multiply the measured
voltage by 2, then used that as the 100% value in the equation.
- Industrial Wireless IoT solution
Page 9 of 11
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