Seed planter sensor

I am looking for a sensor that i can use in a seed planting machine, capable of measuring the number of seeds that are dropped from the planter. The seeds are dropping at very high rate therefore it should be able to distinguish between seeds. Can any one suggest me a suitable sensor?

Bounce them off a piezo impact sensor.

What size / weight?

How many? How fast is "very fast rate"?

Do it like the commercial seed counters do it: DICKEY-john | Unirate Seed Sensor

mikb55:
Bounce them off a piezo impact sensor.

Well the seeds have to be sow in the field, so if bounced from the impact sensor they won't be sowed properly

A simple corn seed

dannable:
What size / weight?

A simple corn seed

usmanqadir91:
A simple corn seed

dannable:
What size / weight?

That doesn't answer either of the questions.

DaveEvans:
Do it like the commercial seed counters do it: DICKEY-john | Unirate Seed Sensor

Yes i want to design something similar to that, what sensors they have used in this?

usmanqadir91:
Yes i want to design something similar to that, what sensors they have used in this?

Didn't you read that page? It's right there.

Optical seed sensors work under the principal of photo detection. Light emitting diodes (LEDs) create a thin field of light across the interior of the seed tube. A photo detector on the opposite side of the tube continuously monitors the intensity of the light. Any seed that disrupts the sensing zone’s light source is detected by the photo detector cell and the corresponding seed pulse is communicated to the monitor.