Sensor question

Hi All,
what I want is a sensor array about 80mm to 100mm in height with 8 to 10 sensors, to monitor packet position on a conveyor does any one know of such a thing or has anyone built something like this ???


Jezz

Big questions to answer:

1. What resolution do you need?

2. What type of output signal do you want from the sensor?

3. What response time do you require?

4. Are the objects to be sensed clear? reflective? opaque?

Answers

1. 8 bit would do

2. PNP

3. 100 ms

4. silver foil

Jezz

What are the different heights that you are looking at differentiating between?

Jezz...

The first step in solving any problem is to clearly define the problem.

Saying... "...I want is a sensor array about 80mm to 100mm in height with 8 to 10 sensors, to monitor packet position on a conveyor..." doesn't cut it. Your problem, as defined, is too ambiguous.

Are you looking to see if the packet is "laying straight" on the conveyor?
Are you looking to see if the packet is "properly oriented" on the conveyor?
Are you looking, simply, to see if the packet is there?
Are you trying to "measure the height" of the packet?
Are you trying to "measure the width" of the packet?

Without us having a sense of what you really need, you are bound to get several suggestions... that don't apply.

Give us a break... help us help you.

In general, there are some light-fences that provide an analog signal which represents the degree of "blockage". Depending on how the device is setup, you could get a higher analog signal with a small packet (low-blockage = higher signal) or a lower analog signal with a small packet (low-blockage = lower signal).

Otherwise, you could go with a couple of digital fence-sets; one tall and one low. If both sets are ON the the packet is tall. If only the shorter one is ON the packet is short. Various vendors provide various resolutions.

Otherwise, you could go nuts and build your own with a dozen photoeye transmitters and receivers. Each mounted at various heights...

Or maybe... mount a transmitter/receiver on a frame on either side of the conveyor and drive the frame with a servo motor with an encoder feeding back height information. The default position would be a hair above the conveyor. When the eye sees something, have the servo motor raise the transmitter and receiver, quickly, until the eye doesn't see anything. At that point, grab the encoder data and scale it to whatever you need.

Let's see... are there any other Rube Goldberg things I can pull out of my hat?