Let me explain... (and no, an angle grinder won't do)

Based on the operation of my automated cat feeder (http://
www.newtonnet.co.uk/catfeeder) I've been asked to develop a similar
device for dispensing nuts to birds. The existing design will be
modified slightly to reduce the amount of nuts dispensed in any one
'serving' however its basic principle will remain the same: a motor
will slowly turn a paddle and provide six servings per revolution.

What I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates, I have decided that my best bet is to somehow detect
the ejection of a bunch of nuts (there'll be less than 10 per serving
i.e. per section of the paddle) once they have left the dispenser.
This detection can then stop the motor turning and await the trigger
for another serving.

I've been experimenting with a break beam detector (a Velleman MK120
hobby-type kit consisting of an IR transmitter/receiver) and whilst
the detector functionally works and is great for detecting even a
finger quickly passing through the 'beam' I am not having quite so
much success with the smaller, and I guess faster, burst of nuts going
through. I have yet to try focussing the falling nuts via some waste
pipe or similar but I'm beginning to think even that might not help
much.

I was wondering if anyone here could think of an alternative, and
hopefully better, way of detecting what is essentially a small amount
of nuts falling out of the dispenser? Perhaps something like a gate
type arrangement attached to a lightweight microswitch that the nuts
fall through activating in the process...? I want to keep things
simple, not only to ensure reliability but also because the budget is
finite and there's a inevitable skillset limitation too!

Does all make sense? Any thoughts would be greatly appreciated and I'm
keeping my fingers crossed that there's a genius idea out there that
I've overlooked...

Mathew

On Wed, 27 Apr 2011 12:58:34 -0700, Mathew Newton wrote:
I've been experimenting with a break beam detector (a Velleman MK120
hobby-type kit consisting of an IR transmitter/receiver) and whilst the
detector functionally works and is great for detecting even a finger
quickly passing through the 'beam' I am not having quite so much success
with the smaller, and I guess faster, burst of nuts going through. I
have yet to try focussing the falling nuts via some waste pipe or
similar but I'm beginning to think even that might not help much.

Hmm, it should be possible - I've used grain counters before and they're
very reliable despite the smaller size of the grains. They held the
grains on a vibrating chute which had a *very* slight slope to it - the
frequency could be tweaked, but too high and grains would pour through
too quick and give false results much like you're getting.

Alternately, are the nuts of uniform enough size that you could use a
slotted wheel to pick one - but never two - up from a hopper and deliver
it past the beam at a "slow enough" speed?

cheers

Jules

On 28/04/2011 10:17, Huge wrote:
On 2011-04-27, Jules wrote:
On Wed, 27 Apr 2011 12:58:34 -0700, Mathew Newton wrote:
I've been experimenting with a break beam detector (a Velleman MK120
hobby-type kit consisting of an IR transmitter/receiver) and whilst the
detector functionally works and is great for detecting even a finger
quickly passing through the 'beam' I am not having quite so much success
with the smaller, and I guess faster, burst of nuts going through. I
have yet to try focussing the falling nuts via some waste pipe or
similar but I'm beginning to think even that might not help much.
Hmm, it should be possible - I've used grain counters before and they're
very reliable despite the smaller size of the grains. They held the
grains on a vibrating chute which had a *very* slight slope to it - the
frequency could be tweaked, but too high and grains would pour through
too quick and give false results much like you're getting.

Alternately, are the nuts of uniform enough size that you could use a
slotted wheel to pick one - but never two - up from a hopper and deliver
it past the beam at a "slow enough" speed?
When I worked for United Biscuits (who own(ed?) KP) I have some brief
exposure to the problems involved in packing mixed nuts and raisins(*). We
only counted brazil nuts, since they were large and expensive - IIRC peanuts
were packed by volume, since they are of reasonably constant size.

(* My real job was weighing flying crisps. Or persuading PDP11s and crisp
bagging machines to do it. This was some time ago, so my knowledge of
the technology is a tiny bit out of date.)


How about having a weighing machine of some type under the bowls and
trigger the stop when the correct weight has been reached.

either mod a electronic scale or make your own pressure sensor.

On Apr 28, 10:17 am, Huge wrote:

My real job was weighing flying crisps. Or persuading PDP11s and crisp
bagging machines to do it.

I remember as a child opening a packet of crisps, putting my hand
inside, and finding what I first thought was a dead mouse... It turned
out to be a single whole potato that presumably must've made its way
through and tripped the bag weighing machine into thinking it was
sufficiently filled!

It was a bit of a shocker and I did wonder if I'd ever be able to eat
crisps again!

Mathew

On Apr 27, 8:58*pm, Mathew Newton wrote:

a motor
will slowly turn a paddle and provide six servings per revolution.

I'd use a stepper motor. it has the advantage of good torque from a
standstill, not requiring a gearbox, and it's also easy to make it run
for a precise number of angular steps, rather than for a time. To
control it you could use an AVR processor (withh minimal bootloader
you can make a low-cost Arduino), a PIC or even an IQ3 from MUTR
(cheap and very simple, if your needs are equally simple)

"Mathew Newton" wrote in message
...
Let me explain... (and no, an angle grinder won't do)

Based on the operation of my automated cat feeder (http://
www.newtonnet.co.uk/catfeeder) I've been asked to develop a similar
device for dispensing nuts to birds. The existing design will be
modified slightly to reduce the amount of nuts dispensed in any one
'serving' however its basic principle will remain the same: a motor
will slowly turn a paddle and provide six servings per revolution.

What I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates,


????

What's wrong with a simple micro switch that stops the motor when the paddle
blade is there.
A momentary operating switch then bypasses the micro switch to start the
paddle turning.
The micro switch closes when the paddle blade moves and opens again when the
next paddle blade pushes it.

"Mathew Newton" wrote in message
...

I was wondering if anyone here could think of an alternative, and
hopefully better, way of detecting what is essentially a small amount
of nuts falling out of the dispenser? Perhaps something like a gate
type arrangement attached to a lightweight microswitch that the nuts
fall through activating in the process...? I want to keep things
simple, not only to ensure reliability but also because the budget is
finite and there's a inevitable skillset limitation too!

I did my share of hacking electronics when I was working in a research lab,
but I'm a mechanical engineer at heart. Assuming you are using the same sort
of three flap dispenser, I'd be inclined to control it electromechanically
with the logical equivalent of cams, microswitches, relays so that it just
does a third of a turn per demand. You could implement this in all sorts of
ways using linkages, gears, chains, etc.

Loved the cat-feeder and site, though!

On Apr 27, 8:58*pm, Mathew Newton wrote:
Let me explain... (and no, an angle grinder won't do)

Based on the operation of my automated cat feeder (http://www.newtonnet.co.uk/catfeeder) I've been asked to develop a similar
device for dispensing nuts to birds. The existing design will be
modified slightly to reduce the amount of nuts dispensed in any one
'serving' however its basic principle will remain the same: a motor
will slowly turn a paddle and provide six servings per revolution.

What I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates, I have decided that my best bet is to somehow detect
the ejection of a bunch of nuts (there'll be less than 10 per serving
i.e. per section of the paddle) once they have left the dispenser.
This detection can then stop the motor turning and await the trigger
for another serving.

I've been experimenting with a break beam detector (a Velleman MK120
hobby-type kit consisting of an IR transmitter/receiver) and whilst
the detector functionally works and is great for detecting even a
finger quickly passing through the 'beam' I am not having quite so
much success with the smaller, and I guess faster, burst of nuts going
through. I have yet to try focussing the falling nuts via some waste
pipe or similar but I'm beginning to think even that might not help
much.

I was wondering if anyone here could think of an alternative, and
hopefully better, way of detecting what is essentially a small amount
of nuts falling out of the dispenser? Perhaps something like a gate
type arrangement attached to a lightweight microswitch that the nuts
fall through activating in the process...? I want to keep things
simple, not only to ensure reliability but also because the budget is
finite and there's a inevitable skillset limitation too!

Does all make sense? Any thoughts would be greatly appreciated and I'm
keeping my fingers crossed that there's a genius idea out there that
I've overlooked...

Mathew

I'm not convinced what you propse is the best option, but it should
work. Check out any pinball machine, looking for a flap where the ball
goes through it, producing a score.


NT

On Apr 27, 10:30 pm, Tabby wrote:

I'm not convinced what you propse is the best option, but it should
work.

You could well be right, but there may be a certain amount of 'better
the devil you know' at play here!

Check out any pinball machine, looking for a flap where the ball
goes through it, producing a score.

Yes, that's an idea...

Mathew

In message
,
Mathew Newton writes
What I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates, I have decided that my best bet is to somehow detect
the ejection of a bunch of nuts (there'll be less than 10 per serving
i.e. per section of the paddle) once they have left the dispenser.
This detection can then stop the motor turning and await the trigger
for another serving.

Just adapt one of these

http://www.youtube.com/watch?feature=player_embedded&v=rWd3vgLaA_M


--
geoff

On Apr 27, 10:54 pm, geoff wrote:

Just adapt one of these

http://www.youtube.com/watch?feature=player_embedded&v=rWd3vgLaA_M

Wow.... That is quite possible the most impressive thing I've ever
seen (made out of Lego at least...!)

Can I get away with claiming that manipulating non-symmetrical and
irregularly-shaped nuts is more difficult that smooth plastic
balls...? No, thought not...

Mathew

On Apr 27, 10:54*pm, geoff wrote:
In message
,
Mathew Newton writesWhat I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates, I have decided that my best bet is to somehow detect
the ejection of a bunch of nuts (there'll be less than 10 per serving
i.e. per section of the paddle) once they have left the dispenser.
This detection can then stop the motor turning and await the trigger
for another serving.

Just adapt one of these

http://www.youtube.com/watch?feature=player_embedded&v=rWd3vgLaA_M

--
geoff

Awe,, Fantastic,,!

They should have it drawin the lotto..


.............................................

"Mathew Newton" wrote in message
...
Let me explain... (and no, an angle grinder won't do)


Biggest hammer then, or duct tape...

Mike

"Mathew Newton" wrote in message
...
Let me explain... (and no, an angle grinder won't do)

Based on the operation of my automated cat feeder (http://
www.newtonnet.co.uk/catfeeder) I've been asked to develop a similar
device for dispensing nuts to birds. The existing design will be
modified slightly to reduce the amount of nuts dispensed in any one
'serving' however its basic principle will remain the same: a motor
will slowly turn a paddle and provide six servings per revolution.

What I want to do is be able to do is trigger only a single serving
and, given the somewhat inexact method by which this paddle delivery
method operates, I have decided that my best bet is to somehow detect
the ejection of a bunch of nuts (there'll be less than 10 per serving
i.e. per section of the paddle) once they have left the dispenser.
This detection can then stop the motor turning and await the trigger
for another serving.

I've been experimenting with a break beam detector (a Velleman MK120
hobby-type kit consisting of an IR transmitter/receiver) and whilst
the detector functionally works and is great for detecting even a
finger quickly passing through the 'beam' I am not having quite so
much success with the smaller, and I guess faster, burst of nuts going
through. I have yet to try focussing the falling nuts via some waste
pipe or similar but I'm beginning to think even that might not help
much.

I was wondering if anyone here could think of an alternative, and
hopefully better, way of detecting what is essentially a small amount
of nuts falling out of the dispenser? Perhaps something like a gate
type arrangement attached to a lightweight microswitch that the nuts
fall through activating in the process...? I want to keep things
simple, not only to ensure reliability but also because the budget is
finite and there's a inevitable skillset limitation too!

Does all make sense? Any thoughts would be greatly appreciated and I'm
keeping my fingers crossed that there's a genius idea out there that
I've overlooked...

Mathew

How about some form of clock escapement idea ?