Choice of sensor for falling objects

Projects General Guidance
1

To start with, I'm an absolute noob here, so please correct me if this is not the right place to post.

If I wanted to detect the number of objects in a box (which fell in), what would be the best choice of sensors? I'm considering:

  1. a vibration sensor (shake switch) that adds to my counter when an object reaches the bottom of the box

  2. IR sensor that detects falling of the object

Which would give more consistent results? Thanks in advance...

2

Please describe or identify the objects.

3

What are these objects (size, shape, material)?
How fast do they fall?
How big is the box they fall in?
Are other sensor options allowed, such as a piezo impact sensor?

4

The objects are medicines in individual blister packs. Perhaps dropped from a height of 1/2m. Would the piezoelectric sensor store charge after mechanical stress is applied? Because I would like the sensor to reset to 0 after every detection.

5

Are objects being dropped in a random pattern and you just want to count the objects that land in the box?

Or is there an object dropper that targets the box and drops the objects in the box and there is a posibility of an object being dropped but not landing in the box?

I'd count the number of objects the object dropper drops and weigh the box, having, previously weighed the box and an individual object to be dropped would get you the number of objects in the box and the number of objects dropped.

6

Well unfortunately there isn't a specific object dropper-and each object weighs differently too!

7

My guess is that the most effective solution is to weigh the box. The weight will increase as each object is added.

...R

8

And more questions!

What is the probability of more than one object hitting the box at the same time?

Is the "box" something that is fixed so it can't be moved or replaced?

Is the "box" apt to echo the sound of your material hitting box so your piezo will not be able to isolate the actual drop from the echo?

Paul

9

Robin2:
My guess is that the most effective solution is to weigh the box. The weight will increase as each object is added.

...R

However, I would like to know the exact number of items inside the box :stuck_out_tongue:

Paul_KD7HB:
And more questions!

What is the probability of more than one object hitting the box at the same time?

Is the "box" something that is fixed so it can't be moved or replaced?

Is the "box" apt to echo the sound of your material hitting box so your piezo will not be able to isolate the actual drop from the echo?

Paul

We can assume that each item is dropped individually. The box is fixed and cannot be moved, yes. Well for the piezo, I guess I could place some acoustic foam material inside, but thanks for bringing that up!

10

Then, at this point, it's up to you to begin experimenting.

Paul

11

grated_cheddar:
Well unfortunately there isn't a specific object dropper-and each object weighs differently too!

So how, exactly, does the 'object' get into the hopper?

  1. Employee tosses from three feet away.
  2. Slides down chute/tube directly in.
  3. Air dropped from height X.
  4. Possibility of multiple simultaneous drops?
  5. Other?

Got any pitchers?

12

grated_cheddar:
However, I would like to know the exact number of items inside the box :stuck_out_tongue:

Then just increment a counter every time the weight goes up.

...R

13

It's a lot easier if you use a load cell.

14

The objects are medicines in individual blister packs.

Any need to identify the medicine being dropped? Placebo pills? Oxycontin?

15

Hi,
If each object is off a different mass and possibly shape, why not make the objects side down a chute into the box.
In the chute you have an optical sensor that senses the object going down the chute.
You count each object.

Tom.... :slight_smile:

16

dougp:
So how, exactly, does the 'object' get into the hopper?

  1. Employee tosses from three feet away.
  2. Slides down chute/tube directly in.
  3. Air dropped from height X.
  4. Possibility of multiple simultaneous drops?
  5. Other?

Got any pitchers?

Just air dropped in. From about the height of a forearm's length. Single drops only.

dlloyd:
Any need to identify the medicine being dropped? Placebo pills? Oxycontin?

Nope.

Power_Broker:
It's a lot easier if you use a load cell.

Robin2:
Then just increment a counter every time the weight goes up.

...R

I think I will try attaching a landing platform to a load cell that increments a counter whenever the weight goes up. Thanks for the suggestions :slight_smile: