Hungry Dog

[Marvo]

Life has been dealing our dog (Fido) a losing hand. Next doors cat has been sneaking in through the dog flap at night and its been eating his food. Fido's been showing all the classic symptoms of depression as well as losing weight because of malnutrition.

I've decided to throw some engineering at the problem and I've built a sprung ramp in front of his dog bowl and installed a hinged lid on the bowl itself. Under the ramp I've mounted two micro-switches which I want to configure so they will operate a solenoid to lift the lid on his bowl. Only problem is I'm not sure how to wire this system and I'm way to lazy to Google for an answer.

There's a couple of things you might need to know;

1. Next doors cat is considerably heavier than Fido due to the extra rations he's been helping himself to over the recent weeks.
2. The two micro-switches are mounted at different heights so that when the lightweight Fido stands on the ramp only the left hand one operates but when the heavier cat stands on the ramp they both operate.
3. The whole system including the solenoid is 230 volts.
4. The cost of the extra dogfood recently has nearly bankrupted me so I can't afford to buy any more components for this project.

Here's a drawing of the system I've built so far, please let me know how to wire it up so the lid will lift only when Fido is on the ramp.

 

[Resu]

Not sure I'm able to attempt this but the effort you've put into this is amazing mate!

 

[Marvo]

Not sure I'm able to attempt this but the effort you've put into this is amazing mate!

Shame Resu, Fido will be disappointed but it's all good

 

[Marvo]

Here's a larger view of the micro-switch showing the contact arrangement.

 

[Happy Jack]

It'll be the right hand microswitch that invariably interrupts the supply to the solenoid, so the solenoid must be fed via the N/C contact there. Therefore the common terminal on that right hand microswitch to be fed via the N/O contact on the left hand microswitch, and 230V supplying the common terminal there.

Tell Fido to keep his chin up.

 

[Marvo]

Thanks Happy Jack, Fido's clinical depression already seems to be getting better Maybe someone can give me a circuit drawing of the finished circuit just to make my life easier.

 

[trev]

A far easier solution would be to simply rig the flap so the cat can get in but not out, then capture it in the kitchen and drown the ****er. problem solved and the only drain on your beleaguered resources will be a screw to stop the egress of said cat.

 

[High Tower]

I would be more impressed if the second micro switch operated a clever cat ----ing device !!

 

[Marvo]

Okay, I went ahead and wired it up;



It works fine, when the lightweight Fido stands on the ramp only microswitch 1 operates and the solenoid lifts the lid on his bowl. When the overfed cat stands on the ramp both microswitches operate and Microswitch2 interrupts the solenoid supply so the lid stays down.


Now we have a small problem. Fido's back on his normal food intake and he's gained weight to the point where he's heavier than the cat. I'd appreciate it if someone can give me an alternative circuit, using exactly the same components, to ensure he still gets all the food.

 

[Happy Jack]

Given your efforts, isn't it about time Fido took a stand and threw his weight about a bit? As the old saying goes, a dog flattened by an opponent can get up again. A dog flattened by conformity stays down for good.

 

[Marvo]

Yeah you're right but Fido's a pacifist through and through, I think it was way too much Lenny Kravitz and second hand ganja smoke in his early days made him a lover not a fighter.

 

[Floody]

I don't understand ho the ramp would manage to hit both switches Marvo? I may just be having a blonde engineering moment.

edit:

never mind. I forgot about the cat. I see why now . The little fattie knocks the circuit off.

 

[Floody]

And as for Fido now becoming the fattie, I'd do away with 1 switch And make so the ramp is only able to knock the switch on at the weight of your dog. I.e the cat won't be heavy enough to lower the ramp to hit the switch

 

[Marvo]

Lol, yeah you could make one microswitch redundant and adjust it for Fido's weight but it kinda defeats the point of the exercise which is to get you guys thinking about different switch configurations and circuits I'm sure now you've got a grasp of the way the system works you can come up with a circuit.

 

[Happy Jack]

The solution is remarkable simple, actually. I'm not going to blurt it out just yet.