Need advice on tilt sensor

Hi
I am looking for a tilt sensor/switch which would get ON only at 180degree angle. I have looked up the mercury and ball tilt switch but they have a range of 45degrees or more. i need a switch which works only at 180 degree. It has to be really small and should not be clumsy as it needs to be fixed to the side arms of the spectacles.And can be powered by button cells.
Something like the image attached

Hi
I am looking for a tilt sensor/switch which would get ON only at 180degree angle. I have looked up the mercury and ball tilt switch but they have a range of 45degrees or more. i need a switch which works only at 180 degree. It has to be really small and should not be clumsy as it needs to be fixed to the side arms of the spectacles.And can be powered by button cells.
Something like the image below

eyeglasses.JPG

Hi,

You might use an accelerometer chip that can sense angle from gravity 'down'..

Example: HERE

Thanks. I have looked at accelerometer and gyroscope , the problem is that with the arduino board it becomes quite bulky. I was wondering if I could replace the accelerometer with a tilt switch. any ideas?

Hi,
I have not seen any tilt switches that activate in only a small range of angle.

You could use an Arduino Nano or Pro Mini to get small size..

Hi,

Not sure if you are still on the issue.
Also note, that I’m not really qualifying to reliable source of advise as I’m quite new in the domain.
But I’m experimenting with combination of accelerometer and gyro sensor (“GY-85 sensor module ITG3200/ITG3205 ADXL345 HMC5883L MODULE sensor”) at the moment.
And what came to me as a surprise (negative one) that these sensors give you relative tilt. You can get from them amount of degrees your sensor was tilted (roll, pitch…) relative to position when you started to measure but at least for now I didn’t figure out how to get true level of horizon with them.
In case I’m correct that you wouldn’t get from it “where horizon is” - your glasses application might require “calibration” or setting up horizon level every time you power it up, which isn’t ideal.