[SOLVED] Please recommend a Tilt sensing device

Hi,

I would like to ask a question on Tilt angle sensing.

If there is an application which requires the device to be on the upright position, and should generate an error whenever there is an oblique angle between device’s top direction and the upright direction, what sensor should be used to detect it?

I read some articles on Wikipedia and there seems to exist a number of solutions, and several types of sensor are capable of doing that. Accelerometer, like those on iPhone, could obviously do it. Among accelerometers, there are 1, 2 and 3-axis type. Besides accelerometer, there also appears to be some tilt sensor whose sole purpose is to measure tilt angle.

My only need is to measure tilt angle from upright direction, which a relatively low (I presume) accuracy: 2° is enough. The smaller the better, and the cheaper the better. Which type should I choose?

Does anyone have experience on this? Could anyone recommend some solutions?



Bob

If you're the kind to make it yourself, you could bend wire into a pendulum within a hoop. This is the first method that comes to mind.

You hook up a wire to each. If the pendulum swings outward and hits the hoop, the circuit is completed.

A hoop 2/10 inch across, and a pendulum 3 inches long, would give you about 2 degrees of movement in any direction.

You might want to put it in a small clear tube or bottle. It will need care to position in properly each time. Come to think of it, any method will need care in setting it up.

And any method using bare wires will be error prone because the wires will tarnish. You might consider tinning the contact areas with solder.

A non-contact method is to suspend a tiny strong magnet within a loop, or coil, or coils of wire. If you can orient the magnet just right, a swing past the coils might generate sufficient voltage or current to amplify and detect.

A ligh-detection method is to put a photo-detector directly under a stationary pendulum. If the pendulum moves a fraction of an inch in any direction, it exposes the photo-detector to light.

Brad,

These hand-constructed devices are applicable in lab environment, but seems not very suitable for volume manufacturing.

By using sensors, do you have any recommendation?

Bob

Among commercial devices there's the type where a blob of mercury (or a metal ball) sits in a small capsule. Tilting the capsule causes the mercury to cover or uncover wires.

Mercury is a natural for this application. However these days it's restricted from being put in most new devices.

If you scavenge you might locate mercury switches like the ones in older thermostats, or the older silent wall switches. You might need two at right angles, unless you can get one that can trigger a tilt signal in any direction.

I forgot about hall effect devices being suitable to detect a tiny magnet swinging. Either one directly beneath (detecting when the magnet swings away). Or 2, 3, or 4 sensors located at the sides.

Brad,

Putting aside security compliance requirements, I wonder if any company would put those primitive, concept-proof solutions in their product. Does there exist some small-sized chips for this purpose?

Bob

This webpage describes chip-size tilt sensors:

Sensor tutorials - Tilt sensors!

Brad,

Thanks, I read study it.

Bob