I/R and Actuator Dilema

I apologize for my ignorance here but I am new to Arduino. I have a situation in which I need some device such as an IR or other mechanism to monitor activity/movement going past it. The goal is if the activity/movement stops the IR would sense this and send a signal to the controller where it would then in-turn activate a linear actuator. I have been told that the Arduino could do this, but again being new I'm not sure what direction to go or where to start. Any help you could give would be greatly appreciated.

if the activity/movement stops

How long for? 1 millisecond, 1 second, 1 minute, 1 hour,... 1 year?

If you tell us what "activity" you're monitoring we'll promise not to tell anyone else. But it would be helpful in suggesting the proper sensor to use.

Thanks for getting back to me. To help understand my project here it is:

I have a wood pellet boiler which heats my house. In an effort to have an ample supply of pellets I built a storage hopper next to the boiler. The pellets are fed from the hopper to the boiler via an auger in a clear pvc tube. The pellets supply can be shut off from the hopper (in the event of a problem) by the use of an R/V type waste gate.

What I would like to do is attach an actuator to the gate arm so that I could control the operation of the gate via a controller which will be monitoring the fuel feed. The thought is that if the controller (possibly an I/R ) senses that no pellets are being fed down the auger tube it would send a signal to the actuator to close the gate where-by shutting down the fuel feed. If the system is allowed to run without pellets being fed it the causes a back draft where-by smoke fills the tube which then travels back to the storage bin and out into my house.

Any help you could give would be greatly appreciated.

Is there some sort of window that light can shine through which could not get through if the chips are flowing?

I suspect it would be hard to detect the difference between chips and the background using reflected light.

Another thought is to have a lightweight flap that is lifted by flowing chips and falls down if they are not - but it could get stuck up.

...R

The feed tube is a 2 1/2" across and it's made of a clear plastic type material. There is about a 1" to 1 1/2' inch of space between the auger and the top of the tube when not feeding pellets. I was wondering if a beam could be shot through this open space of the tube. So if the beam passes through unobstructed this would indicate that there are no pellets and it would signal the controller to close the feed gate. If the beam is interrupted by the pellets then it is feeding correctly and the controller keeps the gate open. I just don't know if the Arduino can do this and if it can where to begin?

DJ2014: The feed tube is a 2 1/2" across and it's made of a clear plastic type material. There is about a 1" to 1 1/2' inch of space between the auger and the top of the tube when not feeding pellets. I was wondering if a beam could be shot through this open space of the tube. So if the beam passes through unobstructed this would indicate that there are no pellets and it would signal the controller to close the feed gate. If the beam is interrupted by the pellets then it is feeding correctly and the controller keeps the gate open. I just don't know if the Arduino can do this and if it can where to begin?

So what you need is something like this: loop start Is beam broken?...yes (pellets are there, so skip the rest of the code)...no, (could be just a gap between pellets) then wait some time (depending on speed of pellet movement) and check again. Is beam broken?... no, then close gate. loop end

If you can reliably detect the presence of pellets the Arduino can easily do the controlling. @Henry_Best has nicely described the process.

As you say there is a clear tube I would be tempted to try detecting with a Light Dependent Resistor as they are very cheap and very simple to use. They generally work with visible light. I guess if the feed tube is in a dark room you would need a light source - and, of course for night time.

I would be wary of a detector that uses a very narrow beam in case a bit of dirt sticks to the plastic tube and blocks the beam path.

You will probably also need a routine for cleaning the tube.

Are there any safety implications if your detector falsely leaves the flap open or closed?

How much fuel will there be in the augur? What if the detector closes the flap if the tube is clear but the augur is not yet empty? Can this happen?

...R

Henry_Best and Robin2, thanks for your input. It sounds like this project could actually work. I'll try and best answer your latest questions:

*You will probably also need a routine for cleaning the tube: I clean the boiler weekly as part of a maintenance routine so I could also include cleaning the feed tube.

*Are there any safety implications if your detector falsely leaves the flap open or closed? If it falsely closed the gate it would then shut off the pellet feed where-by starving the boiler of fuel, ultimately putting out the fire and heat. If the gate does not close when no pellets are detected, (the feed tube would be empty) the boiler would then start drafting smoke back into the tube and storage bin. The smoke then fills the bin and out into my home. This actually happened last week and even set off the smoke detectors. This is why I am trying to come up with a solution to prevent the smoke from filling the house.

*How much fuel will there be in the augur?: When the auger is feeding fuel from the hopper to the boiler, the tube is full of pellets top to bottom.

Thanks again for your help.

My questions were actually just intended to stimulate your own thoughts and plans.

I presume you have no more questions for the moment.

Have fun.

...R