What low-cost sensor detects objects moving between 10kph and 170kph at a 2m range?

[fuee]

Hello fellow humans,

Excuse the simplicity of this question. What I'm looking for is ancient technology, but I have a lot of learning to catch up on. Based on the following details, could you please suggest what sensor (model number preferably) I'm looking for?

1. Detect movement of one of the following 'Objects': 1) " diameter by 1" high hard black rubber 'disk' (speed: 20-170kph), 2) person running by the sensor (assume feet are always on the ground) (5-30kph), and 3) the swipe of a hand (not sure the speed of a typical hand swipe).
2. Movement simply means presence of one of the objects in front of the sensor. If you know of a sensor that can detect speed as well that would be interesting, but not necessary.
3. It's preferred that the sensor doesn't require a reflector or a 2-part system, but it's not out of the question if that's the best option for cost and reliability.
4. The device that the sensors will be used in is the shape of an Apple TV box. The idea is to put sensors on the 4 sides, for detection of all 3 Objects, and one on the top, only for the hand swipe.
5. Use in dark or light environments is preferred, but if only one is an option, then it would be light environments (gym lighting or daylight).
6. The temperature range of the Objects is -20 to 40 degrees.
7. The sensor detection range should be a minimum of 2 meters for the 4 side sensors. Up to 3m is fine, but not necessary. The top sensor, which is just used for the hand swipe could be 1m, if that means using a cheaper sensor.
8. Within 0.2 seconds reaction time is ideal.

Minimum Application:

Detect the presence of an Object when it crosses a plane. Reliability is paramount.

Note:

A normal cheap IR sensor that we tried barely senses 50cm, so that's why I'm looking for a specific model number, if you're aware of something.

If I missed any detail, please let me know! I will happily get into a deeper discussion. Thank you in advance for sharing your knowledge.

Wish you a happy and peaceful day.

 

[D.A.(Tony)Stewart]

For example;
Golf balls can be sensed with a vertical array of interruption IR paths for velocity and height. But for reflection this is a much smaller signal especially if black..
Not all black objects are black with IR so reflectivity must be given. as a % of white and the wavelength used. Black paint has a high coefficient (looks grey) and Sharpie black Ink is very low. Rubber may also be low and is diffused.

So a reflection coefficient test is needed with typical IR LED and/or laser wavelengths., if you can.

170 kph is ~ 47 m/s or 47 mm /ms at zero range but if at a 2m range and a semi circle of 6.28m detection of the object signal is now reduced and is inverse to R^2. This can only be made more linear with a pulsed Laser emitter and very small horizontal viewing angle but a wide vertical detector using AGC to detect small changes.

A 3D sketch of all objects and detection window, as height, distance and viewing angle are all important but sounds like a hockey puck goal sensor.

Waiting for your answers.

 

[BradtheRad]

I'm reminded of equipment that either:

1) detects how fast a pitcher throws a baseball, or
2) radar gun that police use to detect vehicle speeds, or
3) portable cameras turn to follow a subject moving, or
4) porch-mount security cameras detect and focus on subject in field of view.

 

[KlausST]

Hi,

what I miss is: the specification of accuracy and where the sensors are located.

I mean, if the sensors are besides the travel path ... you probably get some speed accuracy error.
But if a doppler radar sensor in exactly "in path" ... the sensor would be hit with your 170kph rubber disc. ... and maybe destroyed.

A sketch with travel path range and angular range and also where the sensors can be located ... would be helpful.
Sizes at all. Are we talking about an indoor living room applicatioin or is it some outdoor application on a football field size.

Klaus

 

[fuee]

For example;
Golf balls can be sensed with a vertical array of interruption IR paths for velocity and height. But for reflection this is a much smaller signal especially if black..
Not all black objects are black with IR so reflectivity must be given. as a % of white and the wavelength used. Black paint has a high coefficient (looks grey) and Sharpie black Ink is very low. Rubber may also be low and is diffused.

So a reflection coefficient test is needed with typical IR LED and/or laser wavelengths., if you can.

170 kph is ~ 47 m/s or 47 mm /ms at zero range but if at a 2m range and a semi circle of 6.28m detection of the object signal is now reduced and is inverse to R^2. This can only be made more linear with a pulsed Laser emitter and very small horizontal viewing angle but a wide vertical detector using AGC to detect small changes.

A 3D sketch of all objects and detection window, as height, distance and viewing angle are all important but sounds like a hockey puck goal sensor.

Waiting for your answers.

Thanks, so much for sharing your thoughts, Tony. You're right. It's a hockey puck. Black hard rubber. Can forget about velocity for now as that complicates things and is a plus, but not a necessity. When the puck crosses a plane, like a goal line, the sensor recognizes it. In this application location relative to the goal line doesn't need to be accurate, as long as the sensor knows the puck is there.

Also, if one kind of sensor isn't feasible to detect all 3 Objects, we can look at what works just for the puck.

 

[fuee]

Hi,

what I miss is: the specification of accuracy and where the sensors are located.

I mean, if the sensors are besides the travel path ... you probably get some speed accuracy error.
But if a doppler radar sensor in exactly "in path" ... the sensor would be hit with your 170kph rubber disc. ... and maybe destroyed.

A sketch with travel path range and angular range and also where the sensors can be located ... would be helpful.
Sizes at all. Are we talking about an indoor living room applicatioin or is it some outdoor application on a football field size.

Klaus

Klaus, thank you for the insightful questions. Imagine the disk (which is an ice hockey puck) going across a goal like. Use environment is an ice rink, gym, driveway, garage, or a location where people can shoot on a goal. When the puck passes the detection window of the sensor, which can be just a line, don't need a wide angle, the sensor is triggered.

Does this help?

 

[fuee]

I'm reminded of equipment that either:

1) detects how fast a pitcher throws a baseball, or
2) radar gun that police use to detect vehicle speeds, or
3) portable cameras turn to follow a subject moving, or
4) porch-mount security cameras detect and focus on subject in field of view.

Hi Brad, these all make sense. Thanks for sharing your thoughts. I'll respond on each one to help define the objective.

1) detects how fast a pitcher throws a baseball, or
- Our primary use case is simply to determine presence of the Object, speed is secondary and not necessary, just an option.
2) radar gun that police use to detect vehicle speeds, or
- These, like a good radar gun, are high cost. We'd like something that's cents, rather than dollars. If it costs dollars then we'd probably need to change the product design to include less sensors per device. Also the distance we're looking for is 2m, whereas the car radar probably works at over 10m.
3) portable cameras turn to follow a subject moving, or
- That's more software, power consumption, and performance than I expect we need. I'm looking for something really simple. Just to detect when a line is crossed.
4) porch-mount security cameras detect and focus on subject in field of view.
- The black disk (hockey puck) can travel up to 170kph. Reality is that we can probably get away with as low as half that though, since we're only sensing it when it's on the ground and usually when it's shot quickly it's a little off the ground.

 

[BradtheRad]

distance we're looking for is 2m, whereas the car radar probably works at over 10m.

Every so often there's a discussion at Edaboard about making a room-sized radar system, either light-transmitted or audio-transmitted. (Often the plan is to mount it on a robot.) Since you wish to detect a moving object, spectral shift might assist. Moving away from your sensor, slightly red. Toward your sensor, slightly blue.

Astronomers use the same strategy. Suppose you watch through a color viewer, yet you adjust stationary objects to appear black or white or gray. Then the slightest color change is a moving object.

--- Updated Today at 3:58 AM ---

Put two identical sensors at a 90 degree angle just like one is on the X axis, and the other sensor is on the Y axis.

 

[fuee]

Every so often there's a discussion at Edaboard about making a room-sized radar system, either light-transmitted or audio-transmitted. (Often the plan is to mount it on a robot.) Since you wish to detect a moving object, spectral shift might assist. Moving away from your sensor, slightly red. Toward your sensor, slightly blue.

Astronomers use the same strategy. Suppose you watch through a color viewer, yet you adjust stationary objects to appear black or white or gray. Then the slightest color change is a moving object.

--- Updated Today at 3:58 AM ---

Put two identical sensors at a 90 degree angle just like one is on the X axis, and the other sensor is on the Y axis.

Hi Brad, appreciate your continued interest. What I'm trying to achieve seems simpler than this. The goal is just to know when an Object crosses 1 axis. For example, knowing when runners cross the finish line of a race or when a hockey puck crosses a 2m line. Any ideas of the lowest cost sensor for this kind of thing? Ideally, one sensor is enough, but if a sender and a receiver is necessary, so be it.

 

[D.A.(Tony)Stewart]

Unfortunately you could not answer my 2 requests.
A fundamental problem is goalie interference with optics at the goal line. Two corner cameras might be the only way with motion detection and pattern recognition.

 

[fuee]

Unfortunately you could not answer my 2 requests.
A fundamental problem is goalie interference with optics at the goal line. Two corner cameras might be the only way with motion detection and pattern recognition.

Hi Tony, apologies, I didn't pick up on the requests. In this case there is no goalie, so no interference. What is the second request?

 

[BradtheRad]

The goal is just to know when an Object crosses 1 axis.

I pictured boots in the background, a mixture of black & white pixels. It's starting to seem like an overhead view is sufficient. Is the background white ice? Have a camera shoot one picture per 1/100 sec. During the next 1/100 sec count black pixels.

a) If the tally is different, then you detected movement.

b) Or if the location of black pixels changed since the previous picture, then that detects movement.

c) Or if a group of black pixels follows a straight line compared to two previous images, then that detects movement.

 

[KlausST]

Hi Brad, appreciate your continued interest. What I'm trying to achieve seems simpler than this. The goal is just to know when an Object crosses 1 axis. For example, knowing when runners cross the finish line of a race or when a hockey puck crosses a 2m line. Any ideas of the lowest cost sensor for this kind of thing? Ideally, one sensor is enough, but if a sender and a receiver is necessary, so be it.

so .. you don´t want to measure the speed ... you are just interesteed in the "position".
I have to admit, since your headline talks about "moving" and "speed" ... I was focussed on speed measurement.
Now I see I was wrong.

Still a sketch with some dimensions would be helpful. It is way more informative and "international" than text.

Klaus

 

[FvM]

- These, like a good radar gun, are high cost. We'd like something that's cents, rather than dollars. If it costs dollars then we'd probably need to change the product design to include less sensors per device. Also the distance we're looking for is 2m, whereas the car radar probably works at over 10m.

First time that you come up with quantitative specs. There are however some wrong assumptions and specs are still partly vague.

You should clarify if you need distance discrimination. If so, the sensor choice is narrowing to ultrasonic, RF or light TOF or RF FMCW principles.

There are chip level IR light TOF distance sensors available, e.g. from ST. Also ultrasonic TOF is an option for cheaper solutions.