Tilt/tip sensors to control movement of cylinder

[ktko]

This is for a product design class, and I have very little electrical knowledge. My design is a trash can which locks when it is tipped over (or tipped to a certain degree). The lock would be simple, likely some kind of cylinder (or pair of cylinders) that would block the lid flaps from opening.

I was thinking of some kind of tilt sensor.
So my question is: if I want the cylinders to move once the tilt sensor reaches a certain degree, how would I do that?

The cylinders would likely be recessed into the housing of the trashcan lid. Not sure about the placement.

I don't need to actually build this product, but I want to at least understand how the electrical components work, or what i would need in order to make it work

Also....I've read that tilt sensors need to be run on AC current, are there any that can be run on some kind of battery? Or is there any way to get an AC current without having to plug it into the wall?


Any input is appreciated!
Thanks!

 

[d123]

Hi,

The brief datasheet for this range says 6mA/24V DC, that would be maximum ratings I would hope...

Tilt Switch Ball-Rolling Switch AT Series

The description on Sparkfun for it says that when moved the contact between ball and pins is lost, so it's a normally closed (NC) device. So, I'd guess, and there will be better solutions than this suggestion, a comparator used to sense closed circuit (level bin) and open circuit (bin falling over) connected to a drive transistor, driving a solenoid used to lock the bin lid, may be a solution; the battery part may make that solution not so viable if it is a 3V/ very low mAh type battery.

 

[d123]

Hi,

By trashcan do you mean a municipal wheelie-bin, or one in a kitchen in a house? Big difference... Thinking about simple solutions I can come up with, maybe a spring-loaded hook or a push solenoid are the simplest options. Cylinders are perhaps more expensive as inital cost and maintenance, and I'm not sure even necessary if the premise is a bin whose lid locks shut when toppled over, with a sensor that senses a sudden change of orientation/inclination.

Sorry about the childish paint drawing, just to express the idea(s) a bit, and I'm not implying the battery power the circuit through the tilt sensor, just wanted to keep supply lines and so on out of the kindergarten grade simplified schematic.

- - - Updated - - -

I've had an even better idea It's tongue-in-cheek, but maybe not as stupid as it looks...

Thinking of greenhouse vents, that require no electricity or circuitry to function quite well, and are far cheaper than electronic pistons and cylinders:

Gravity is a good, but perhaps slightly slow, tilt switch too...

BTW, does the project bin have one lid opening or two - one on either side, like some wheelie-bins?

 

[ktko]

Thanks d123! I haven't read all your replies, skimmed em quickly as I was excited just to see that I had gotten a response.
I can upload some of my sketches if that helps.

But as far as the "trash can" I am thinking more along the lines of an indoor kitchen trash can. (This started out as a "dog proof" trash can, for people who maybe don't have extra cabinet space to hide the can....although now I guess it could potentially be marketed as a "safe trash can")

As it stands now my design has a 2 flap lid. Flaps connected by a hinge to the lid. Flaps open inwards (down) and there is a counterweight on the outer parts of the flaps (the parts hidden by the lid, towards the outer edges of the can) which would raise the lid flaps back to their resting point (the closed position).

The main problems I'm trying to deal with are:
*dogs being able to completely remove the lid (with or without knocking the whole can over)
*dogs figuring out "special" opening mechanisms (step-pedal, push-to-release type lids, sensors)
*dogs knocking the cans over to easily access the trash inside (whether the lid stays on or not, they can usually get into by that point)
* All of the above, without complicating the user's daily interactions (I've had suggestions to keep the lid locked until you need to throw something away....but then you'd have to push a button just to throw stuff away and who wants that?)
A little bit of complication is expected on a weekly basis (taking trash out, replacing bag), as I have the lid attaching to the can using a pair of spring pull latches. (To separate lid from can, you'd pull both latches and lift up, nothing crazy, just something most dogs wouldn't physically be able to do)

A gravity controlled locking device was my first thought....but I had trouble finding examples of that kind of device in use. (Perhaps I was just looking in the wrong places?)

Originally I hadn't planned on having electrical components, but this is where my research has lead me. If you guys think there is a better/easier way, I'm all ears.

I'm in the VERY early stages of a manufacturing/mechanical engineering program. And honestly the most electrical work I've done is installing a new cd player in my car so.....bear with me lol.


(^^ I wrote this out of order, hopefully it still makes sense)

Time to go back and read your replies thoroughly

 

[d123]

Hi,

Thanks for the bin description, this afternoon the words DOG + KITCHEN BIN came to mind, they're crafty like that, I've seen them in action , your description of bin and purpose(s) helps to understand the motivation.

One thing, the greased telescopic tube idea is the wrong way round: telescopic bit would have to go on lid, and receiver tube on bin body to work, and I suspect be inclined at a minute angle from the horizontal to slip out well, and only in one direction... Not a good design after all.

I think perhaps, based on the little I know and the double, inward-opening bin lid, that a push (outwards) solenoid via a circuit responding to the tilt switch could be a solution, as only when the bin is tipped over in any direction the circuit would trigger and the solenoid stick could lock in place to a latch, e.g. a suitable diameter (metal hoop or rigid plastic) fitted into a plastic housing, pre-designed in as part of the bin lid plastic moulding, the same space needed to fit the solenoid, with suitable plastic, not something that melts/goes gooey at low temperatures, if that can be visualised.

Maybe you could look at muscle-wire to hold the lids taut only when tipped, not sure how sturdy that would be, and would probably need to be outside the bin so I'd avoid that as it could be an electrical risk for animals (and humans obviously) if additional housing is not included to cover it fully and robustly.

I'll keep thinking of bad suggestions, if any more come to mind, what I would say is that a) this would use quite a lot of power, even if only on sporadically, and b) it raises the price of a bin considerably, unless you're manufacturing thousands of them. i.e. Normal cat flap: 15 GBP, microchip tagged pet cat flap (has a sensor, microcontoller type IC and a latch mechanism added): ~80GBP...

The benefit of the 17mm action push solenoid is (you can get them for about $15 - $18) that one should keep both a single and a double-lid type locked shut, plus the tilt switch, another $15 at least, then other parts, add maybe $10 - $20; plus (your) labour...$$$: that's a niche market or one-off labour of love device, marketable to people sick of tidying house and stains from carpets on returning home, maybe!! A passive, electricity-free version is perhaps worth racking brain over, if it exists.