[General] Finding the right sensor

[Iroh]

I'm new to electronics and working towards a project. I was hoping someone could help me choose the correct component for my constraints. I'd like to know what type of sensor I should be using. It needs to : Sense mechanical motion, a towards and away from motion to be more specific, be able to detect in complete darkness, hopefully be relatively small... say fit in a 1/2" by 1/2" space, but as small as possible is best, sense the motion which could be intermittent or move very quickly, say 800 movements per minute, be able to send the detection signal to a counter, which is counting down from a preset number, hopefully not consumer too much electricity so it could run from a cell or a battery. A good operating temperature range wouldn't hurt too, nothing extreme, just say what a human can handle.

Is there a sensor that meets these constraints? I'm having a hard time piecing this together. I've done a few projects like a burglar alarm and human reaction timer, etc. but nothing purpose specific from scratch. Please point me in the right direction. Any help would be greatly appreciated!

 

[milan.rajik]

PIR sensors and accelerometers. But I am not sure whether PIC sensors can be used to detect motion of objects. It detects human (/ animal) moton by detecting IR radiation.

 

[Iroh]

PIR sensors and accelerometers. But I am not sure whether PIC sensors can be used to detect motion of objects. It detects human (/ animal) moton by detecting IR radiation.

The sensor would be fixed as well as the mechanical motion it is detecting. They would both be housed inside of an enclosure. The counter would be placed elsewhere in view and connected to receive signal. Ideally the sensor would be able to stand a shock such as being dropped without registering anything or breaking, as the complete package can be carried around by a person and not be affected by their movement or actions but still sense the mechanical motion in the object.

The movement I'm trying to quantify is a machined metal piece that is spring loaded and moving to and fro. If it is touched by anything it will disrupt its function. I need a way to visually detect its motion without affecting its action. It will be inside of an enclosure so it will be without a light source. Would infrared work? It's going to be in a rather tight and narrow space. The object to be sensed will be under a half in at it's closest and about 2 inches at furthest considering the to and fro motion.

I appreciate the response but I'm not well informed on sensors and it seems there isn't as much readily available info out there on the topic, at least not as readily available as simple electronics. The application I'm looking to use it in will be very narrow and point specific basically so I'm kind of scratching my head on this one.

 

[FvM]

"A picture is worth a thousand words"
Your posts reveal the wisdom of this saying...

 

[Iroh]

"A picture is worth a thousand words"
Your posts reveal the wisdom of this saying...

I apologize for being so descriptive and yet visually vague, however intellectual property being what it is I see a lot of potential for what I'm working on and to include a picture would most certainly spoil any future business potential.

 

[milan.rajik]

Can you fix a small sensor to the movable object or make a small device which can be fit on the movable object ?

 

[FvM]

I'm not asking for application details, just a description of intended sensor principle. Despite of your verbose posts, I'm yet unable to understand at least the required working principle.

A sensor can e.g. detect absolute movement of a system in space (acceleration, inclination) or relative movement of two systems (distance variation, rotation).

 

[milan.rajik]

Can you fix two sensors like IR emitter + detector or laser emitter + detector pair in the enclosure and then the moving object if moves forward then blocks the laser or IR and then it can be sensed by the detector and counted. How much the object move, 1 mm, 1 cm , 1 in ?

 

[Iroh]

I would like to be able to do that however the movable object is highly sensitive and any addition weight or interference would upset the timing and function of the device.

 

[Gorgon]

From what's said I would think an active optical sensor should do the job. Like a reflected beam, or two if the movement needs it. If the movement is along one axis you should only need one.

A PIR detector is of no use since it is based on temperature differences, and I think the temperature inside a closed box is relative uniform.

 

[milan.rajik]

Provide the distance the object can move. Min and Max displacement it can have. Is it like a shaft ? Do you want to detect the slightest movement ?

If you want to detect motion of 1 mm and also 10 inch then use an array of photo (IR) or Laser detectors along the axis of movement and below the moving part and then which detectors are activated or not will tell you about the movement but it will not give you info about how much it moved. It is like which sensors are covered by shadow or not.

 

[Iroh]

Provide the distance the object can move. Min and Max displacement it can have. Is it like a shaft ? Do you want to detect the slightest movement ?

I will try to draw up a diagram to hopefully explain the action and position better this evening as well as some measurements. Within the given space there is not ample room to position detector/emitter where the plane would be unbroken/broken. I think that it would be continuously interrupting the beam with the limited room I have to work with, but I'll have to double check to be sure. I really do appreciate the feedback, it's helping me to think in new ways. Is there a sensor that exists that would be able to gauge it by proximity. The action to be measured would be akin to the drinking bird toy in this link. https://www.kleargear.com/7025.html Imagine the sensor as the glass of water and the thing to be measured is the point at which the birds head is close to the water glass. Mind you, they would not touch.

 

[milan.rajik]

You a good light source inside the enclosure and use a high resolution and very sensitive camera. If the object moves even slightly then the image falling on the camers changes and hence image data changes. Compare this image data with previous image data and if it doesn't match then it means object has moved. Write an algorithm to convert image data to amount of displacement.