hello! i am planning to create an automatic pet feeder for my school project. And i am looking for a weight sensor that can detect if the container is already empty or not. thanks....

 

instead of a weight sensor ..
how about a micro switch mounted on a conventional scale .. then as the dial passes tward zero it will tell you when it needs to be filled..

 

The food is opaque, so use an LED and photo transistor. The weight is small and vibration will be a problem.

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i dunno if this would be too simple for you.

if the food comes out onto a dish that has springs beneath it, when there is not enough food, the dish would go higher because there is not enough weight to hold it down. If the dish were a conductive metal, it could touch a metal plate and complete a circuit that would actuate a solenoid that would open a slot to let food spill onto the dish.

like i sed, it mite be 2 simple.

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I'm no electronics god, i just talk too much.

 

Very interesting. I'm working on an automatic pet watering system myself. I'm pretty far into it. Haven't bought the parts yet, but I'm pretty sure I've got everything figured out as far as the construction of it goes. While I can't think of anything now, I'll be thinking of ways to help you. I've been trying to figure it out myself because it'd make a nice addition to my watering machine and save me a few minutes everyday of feeding my 3 dogs and cat. Also, when is this project due? I need to know how hard I have to think. :lol:

Rain

P.S. If you are interested in the machine I'm working on or want to talk about your machine (which I'd actually like to hear more about), E-mail me at electric_boy_2000@yahoo.com.

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I'm not sure if this will work for you, but you could use a photocell mounted in the bottom of the bowl. That way when it's empty, light will shine on the photocell, but when food is in the bowl it will block the light. The only problem is it won't work in the dark. And you may have to do some minor adjusting using a potentiometer depending on how bright or dim the room is.

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If you take a small piece of Antistatic foam and stick a wire in each end, you can make a simple presure sensor. The foam acts as a variable resistor and changes value as the foam is squashed.
~Mike