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PROXIMITY SENSOR FOR CAMERA TRIGGER
MAT from United Kingdom  [4 posts]
8 years
Hi,

I would like to use a proximity sensor to trigger my camera. Actually I use a conventional Trust webcam. Do you know if there is a function in RoboRealm to read the signal from the sensor and so control the capture of a frame? I think I need to read the input variable (sensor signal) through a specific function.

Iīm going to buy an ImagingSource camera which is provided of trigger. The problem is that I donīt if I can use (and how) this attribute (trigger).
Any idea?

Thanks in advance.
Anonymous 8 years
Mat,

What is the purpose of the trigger? Are you not able to just keep capturing frames AFAP and then just save the one that is of interest based on some image quality? Ie. if you are using a flash to sample a scene at a very distinct moment the best image will have the brightest lighting and thus would be the one saved?

Other than that, you'd have to figure out how the trigger is connected to the PC. Are you thinking serial, parallel, ethernet, etc. type of physical connection? That's the first step in determining how RR might be able to access that signal.

The other possibility is if that trigger is available to the DirectX system via a custom property. It might be possible to setup RoboRealm to read that property into a variable that can be accessed and used. Which model ImagingSource camera are you going to purchase.

STeven.
MAT from United Kingdom  [4 posts] 8 years
Thanks Steven for your quick response. In my application I monitor a printing process. So, every time the carriage passes below the camera I need to acquire a frame. I tried to do it analysing "movement percentage" variable. Every times motion=0 the camera is triggered and it saves the actual frame. The problem is that this strategy is not enough consistent.  For this reason I thought to use a proximity sensor. As you suggested, I could connect the sensor to the serial port (or other port) and read the clean signal coming from the sensor. My knowledge on serial communication and protocols is quitew limited. Could you explain me how to read from the serial port in RR?

Many thanks in advance.
Mat.
Anonymous 8 years
Mat,

Do you think you could create a short clip that shows the carriage passing by and then identify which image in that clip would be the one that you'd like saved? I think there may be a way to just do this visually without needing a proximity sensor.

If you go the proximity sensor route you will need an extra board that will read the sensor directly and then communicate its value over serial. The sensor will probably not do that directly depending on the sensor you get. So, you'd need something like a Axon, Basic Stamp, Serializer, Phidgets, etc. in order to get access to that information.

You might be able to connect the sensor directly to the parallel port but you'd need circuitry to adjust for voltage levels. It is best to buy one of the above MCU's in order to perform that interfacing job.

You would not be able to connect the sensor directly to the serial port ... the serial protocol needs to be implemented by the device in order for any serial information to be read. At that point you'd use the RoboRealm serial module to read in that value ... which you still would use with one of the above MCU's.

STeven.
MAT from United Kingdom  [4 posts] 8 years
Thanks Steven. I donīt have just the carriage passing through, but also the printheads that move along the axis of the carriage. So the scenario is a bit more complicated, as I don't have a single event (image) which identify the right moment to capture. For example, both the carriage and the printheads appears a black object, so the camera is not able to distinguish between them. In addition, during a printing phase the printheads pass below the camera multiple times. So, I donīt have a single black frames to be used as trigger. Have a look to 3D printing at http://www.youtube.com/watch?v=R-JOJ91p9Wc so you better understand the process.

Second way: Proximity sensor. I've seen that some camera of ImagingSource are provided with a trigger. I guess that connecting the proximity sensor to the trigger should work as expected. Could you tell me if this makes sense?

Thanks for your patience.
Mat
Anonymous 8 years
Mat,

Sounds good. Unfortunately we're not 100% sure about the trigger on the camera and what kind of signal that requires. It would be best to ask ImagingSource what that trigger signal requires in terms of a signal. You'd then probably need a device to generate that signal based on the results of the proximity sensor. I would imagine that they have probably had similar requests to yours since it seems like a fairly generic task to snap images based on the presence of an object.

STeven.

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