Seed sensor with lightpipe photodetect assembly
In one example embodiment, a seed sensor is disclosed adapted to fit a conventional mounting location in existing seed tubes that provides improved performance by providing a wide light source (more LEDS), a wide photodetector and a current profiling scheme for the LEDs that provides more light at the opposite ends of the LED array. A result of such an arrangement is to improve seed resolution and to reduce seed spatial variability within the seed tube.
1. A seed counting sensor for use with seeding machines, the sensor comprising:
a detection chamber or area within a housing or seed tube, the detection chamber or area allowing the seeds to pass through the sensor having a center longitudinal axis extending in the flow direction of the seeds;
a plurality of light sources arranged within the housing or seed tube at predetermined distances from each other, the light sources being in a plane extending substantially perpendicularly to the center axis of the sensor;
a plurality of light detectors arranged within the housing or seed tube at predetermined distances from each other, the light detectors being in substantially the same plane as the light sources, wherein the number of the light detectors equals the number of the light sources; and
a signal processing unit or controller for controlling operation of the light sources and for processing electronic signals produced by the light detectors in response to interruptions of light received from the light sources;
wherein the sensor further comprises optical adapters arranged in front of the light sources and the light detectors, respectively, the optical adapters configured to form a sight waveguide to channel light from the light sources to the light detectors;
wherein the light sources are separated from each other, and
wherein the light sources and the light detectors are arranged in the plane so that they are capable of scanning substantially the entire cross section of the detection chamber or area.
2. The seed counting sensor according to claim 1 , wherein the light sources are LEDs and the light detectors are phototransistors.
3. The seed counting sensor according to claim 1 , further comprising a control circuit for regulating the light intensity of the light sources as a function of the light intensity detected by the light detectors.
4. The seed counting sensor according to claim 3 , wherein the controller and the control circuit change a drive current of the light sources caused by dust in the seed tube.
5. The seed counting sensor according to claim 1 , wherein the optical adapter are made of plastic.
6. The seed counting device of claim 1 further comprising a window or a light transmissive plate protecting the light sources.
7. A method of improving seed detection within a seed tube caused by deteriorating optical properties of one or more seed sensors, the method comprising the steps of:
providing a sensor assembly adapted to be mounted on the seed tube, the sensor assembly including a plurality of light sources disposed opposite a plurality of photodetectors adapted to receive light from the light sources, the photodetectors configured to generate output current signals in response to interruptions in light received from the light sources, the light sources being disposed in a line that is substantially perpendicular to a longitudinal axis of the seed tube;
processing the output current signals received from the light detectors; and
controlling a current driving each of the plurality of light sources and changing the drive current of the light sources to increase the intensity of light in the seed tube received by the light detectors.
8. The method of claim 7 , wherein the light sources are LEDs and the light detectors are phototransistors.
9. The method of claim 7 , wherein the light sources include a window protecting the light sources and deterioration of the optical properties of the seed sensors is caused by at least one of pelleting agents deposited on the windows and dust.
10. The method of claim 7 , further comprising the step of providing an optical adapter to at least one of the light detectors to collect light from the corresponding light source.
11. The seed counting device of claim 1 wherein the controller is configured to substantially distinguish among multiple seeds.