Photoelectric Eye
17 year
Does anyone have any suggestions on how to use a photoelectric sensor as an input that could be used as an external signal to trigger an analysis of a usb cam image. Any help would be appreciated.
Anonymous 17 year

That would depend on what the photoelectric sensor is connected to. Is it a PC or a microcontroller? Also, I'm a little confused as to why a photoelectric sensor would be used instead of just using the usb cam image to look for the same photo trigger? Is the sensor in a different location than the camera?

Anonymous 17 year
I am new to RoboRealm and vision in general. I am tinkering with developing a machine vision application. My thought was that I wanted to trigger a specific moment when roborealm should analyze the constant imagery being provided by my webcam. In other words I want to analyze my video image once a moving part is centered in the video frame. Not before or after. Not sure how to do this. I am also trying to figure out how I could control actuators, air blast valve etc. that would run on 12V electricity. I currently use PLC's to do this but am not sure how to interface my computer with I/O that is common to sensors, actuators etc. not sure how to do this with the paralell port interface. Any help would greatly be appreciated. I am having great fun with roboRealm.
tawsif from Mauritius  [7 posts] 17 year
if I am not mistaken buddy, u are trying to detect the presence or absence of something in the field of view of the camera and then take appropriate decisions   using ur PLC.
to detect the presence or absence of an intruder, u should constantly subtract the frame which u are receiving with the previous one. I think Roborealm contains a module that will do this task for u.
I have tried the parallel port module of RR and it works well.
I suggest that u  use DB25 female connector adhered with 8, 470 ohms resistors and 8 leds.Brouse a bit on the web to see how this connection is made and then try to play around with the parallel port module of RR.
to interface the parallel port with u PC through the parallel port, I think that ur PLC may accept only 24V inputs. but u trigger the parallel port, only 5V will be outputted.
therefore u need additional circuitry to convert the 5V TTL to 24V.
for example, u can use optocouplers and mosfets to provide the interface.
optocouplers are used to provide for electrical isolation while the mosfet will trigger the 24V for u.
u can use the TIP120 transistor instead of mosfets. this will eliminate the conception of gate drives which may be cumbersome for u.
i suggest u to browse a bit on the web.
search for parallel port interfacing
U should be getting some interesting projects.
May be Steven will try to help u more in this matter.
I'll try to get u the circuitry next time.
U Should mention which PLC u are using;is it an Allen Bradley or a Siemens?
Try to have a look at robotics projects also.
Anonymous 17 year

That's a lot to work on! Perhaps if we start with the first task of getting RR to process when needed. Or you can think of it as RoboRealm is always processing but just reacting to the results when required. For example, if you run RR and use the movement module to detect movement you could trigger a communication or set a variable when enough movement is see. If you check to see how much movement is created using

if GetVariable("MOVEMENT_PERCENT") > 50 then

  SetVariable "action_seen", "1"

end if

inside a VBScript module after the Movement module and then use the variable action_seen in excluding part of the RR pipeline using the IF_STATEMENT module you can prevent certain parts of the RR pipeline from being processed or sending parallel port signals until enough movement is seen.

Does that make any sense?


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