08-10-2012, 03:37 PM
Miniature Ambient Light Photo Sensor with Digital (I2C) Output
[attachment=35675]
Description
The APDS-9300 is a low-voltage Digital Ambient Light Photo Sensor that converts light intensity to digital signal output capable of direct I2C interface. Each device consists of one broadband photodiode (visible plus infrared) and one infrared photodiode. Two integrating ADCs convert the photodiode currents to a digital output that represents the irradiance measured on each channel. This digital output can be input to a microprocessor where illuminance (ambient light level) in lux is derived using an empirical formula to approximate the human-eye response.
Application Support Information
The Application Engineering Group is available to assist you with the application design associated with APDS-9300 ambient light photo sensor module. You can contact them through your local sales representatives for additional details.
I2C Protocols
Each Send and Write protocol is, essentially, a series of bytes. A byte sent to the APDS-9300 with the most significant bit (MSB) equal to 1 will be interpreted as a COMMAND byte. The lower four bits of the COMMAND byte form the register select address (see Table 2), which is used to select the destination for the subsequent byte(s) received. The APDS-9300 responds to any Receive Byte requests with the contents of the register specified by the stored register select address.
Interrupt Control Register (6h)
The INTERRUPT register controls the extensive interrupt capabilities of the APDS-9300. The APDS-9300 permits traditional level–style interrupts. The interrupt persist bit field (PERSIST) provides control over when interrupts occur. A value of 0 causes an interrupt to occur after every integration cycle regardless of the threshold settings. A value of 1 results in an interrupt after one integration time period outside the threshold window. A value of N (where N is 2 through15) results in an interrupt only if the value remains outside the threshold window for N consecutive integration cycles. For example, if N is equal to 10 and the integration time is 402 ms, then the total time is approximately 4 seconds.
When a level Interrupt is selected, an interrupt is generated whenever the last conversion results in a value outside of the programmed threshold window. The interrupt is active–low and remains asserted until cleared by writing the COMMAND register with the CLEAR bit set.
Optical Window Dimensions
To ensure that the performance of the APDS-9300 will not be affected by improper window design, there are some criteria requested on the dimensions and design of the window. There is a constraint on the minimum size of the window, which is placed in front of the photo light sensor, so that it will not affect the angular response of the APDS-9300. This minimum dimension that is recommended will ensure at least a ±35° light reception cone.
If a smaller window is required, a light pipe or light guide can be used. A light pipe or light guide is a cylindrical piece of transparent plastic, which makes use of total internal reflection to focus the light.
The thickness of the window should be kept as minimum as possible because there is a loss of power in every optical window of about 8% due to reflection (4% on each side) and an additional loss of energy in the plastic material.
[attachment=35675]
Description
The APDS-9300 is a low-voltage Digital Ambient Light Photo Sensor that converts light intensity to digital signal output capable of direct I2C interface. Each device consists of one broadband photodiode (visible plus infrared) and one infrared photodiode. Two integrating ADCs convert the photodiode currents to a digital output that represents the irradiance measured on each channel. This digital output can be input to a microprocessor where illuminance (ambient light level) in lux is derived using an empirical formula to approximate the human-eye response.
Application Support Information
The Application Engineering Group is available to assist you with the application design associated with APDS-9300 ambient light photo sensor module. You can contact them through your local sales representatives for additional details.
I2C Protocols
Each Send and Write protocol is, essentially, a series of bytes. A byte sent to the APDS-9300 with the most significant bit (MSB) equal to 1 will be interpreted as a COMMAND byte. The lower four bits of the COMMAND byte form the register select address (see Table 2), which is used to select the destination for the subsequent byte(s) received. The APDS-9300 responds to any Receive Byte requests with the contents of the register specified by the stored register select address.
Interrupt Control Register (6h)
The INTERRUPT register controls the extensive interrupt capabilities of the APDS-9300. The APDS-9300 permits traditional level–style interrupts. The interrupt persist bit field (PERSIST) provides control over when interrupts occur. A value of 0 causes an interrupt to occur after every integration cycle regardless of the threshold settings. A value of 1 results in an interrupt after one integration time period outside the threshold window. A value of N (where N is 2 through15) results in an interrupt only if the value remains outside the threshold window for N consecutive integration cycles. For example, if N is equal to 10 and the integration time is 402 ms, then the total time is approximately 4 seconds.
When a level Interrupt is selected, an interrupt is generated whenever the last conversion results in a value outside of the programmed threshold window. The interrupt is active–low and remains asserted until cleared by writing the COMMAND register with the CLEAR bit set.
Optical Window Dimensions
To ensure that the performance of the APDS-9300 will not be affected by improper window design, there are some criteria requested on the dimensions and design of the window. There is a constraint on the minimum size of the window, which is placed in front of the photo light sensor, so that it will not affect the angular response of the APDS-9300. This minimum dimension that is recommended will ensure at least a ±35° light reception cone.
If a smaller window is required, a light pipe or light guide can be used. A light pipe or light guide is a cylindrical piece of transparent plastic, which makes use of total internal reflection to focus the light.
The thickness of the window should be kept as minimum as possible because there is a loss of power in every optical window of about 8% due to reflection (4% on each side) and an additional loss of energy in the plastic material.