Allen Bradley Photo Sensors

[chrisinmd]

Hello all.
Hope everyone's season is going well so far.

We were using the Allen Bradley sensors in the kit on our robot, and they were working great, but last week they mysteriously stopped working, while we were at Pittsburgh. Now that we're home I have been playing with them and they are still non-functional. Anybody else have this problem? Anybody know where I can get new ones or similar replacements? I haven't been able to find replacements anywhere, and we only got one set in the kit.
Thanks,
-Chris

[TubaMorg]

Hope this doesn't happen to us! So have you tested to make sure they are getting power (12v)? What I really dig about them is that you can trouble shoot them whether they are plugged into the RC or not, all you need is the 12 volts. The red LED on the back of the Receiver lights up when active, but I'm guessing you already know all this. Random thought, isn't there some way to actually 'see' the IR light? Like some special goggles or something? Another thing to check (after you verify your sensors actually have power): There are sensitivity pots that can be fiddled with depending on the application. If you are using a "broken beam" type of scenario, the sensitivity can be dialed down, but if you are using reflected IR (like we are) then you have to turn it up. Establish the conditions that should turn your sensors on, then turn the pots until the red light appears.

If none of that works, then I guess you have to get new ones (you would have to get them from the supplier). Isn't it strange how you can load a perfectly good robot in a crate then two weeks later open it up and pull out a broken one? Seems to happen over and over again

[Eldarion]

Originally Posted by TubaMorg

Random thought, isn't there some way to actually 'see' the IR light? Like some special goggles or something?

Many CCDs, such as those found in digital cameras/camcorders, are very sensitive to infrared light.

Simply aim the emitter at your camera, and a bluish-white light should show up if the emitter is working.
An old black-and-white camcorder will have greater sensitivity than a color one, and a Sony camera in NightShot mode will allow you to see infrared like you would see any other light source, including reflections.

[chrisinmd]

Originally Posted by Eldarion

Many CCDs, such as those found in digital cameras/camcorders, are very sensitive to infrared light.

Simply aim the emitter at your camera, and a bluish-white light should show up if the emitter is working.
An old black-and-white camcorder will have greater sensitivity than a color one, and a Sony camera in NightShot mode will allow you to see infrared like you would see any other light source, including reflections.

Thanks for the help, guys.
Using the camera to test the emitter is a great idea, I might try that. I did play with the sensitivity adjustments, but the test LED remained ON, even when it wasn't directed at the emitter. Lining them up and breaking the beam only caused the LED to dim slightly, instead of going out completely. My colleague and I are completely stumped, and are out of ideas.

Also, does anyone know why there is a sensitivity adjustment on the emitter module? What does it do? Does it change the intensity of the IR beam?

Thanks,
-Chris

[TubaMorg]

well with the LED on at least you know it has power (12v right?). Maybe there's a short somewhere? Our robot is still in the crate so I'm trying to remember...The receiver has 4 insulated wires, 1 for ground, 1 for +12 and the other two for signal. When you strip down the outer cable insulation there is also foil and a bare wire right? Make sure none of that is shorting. I would think that with the LED always on the sensitivity is set too high. Or check the lenses and make sure they aren't blocked or smudged or something...clean em off.

Good luck!

EDIT: Oh BTW the adjustment for the emitter changes the IR beam intensity. But since your receiver is showing an LED even without the transmitter, focus on that problem first.

[Dale(294engr]]

Originally Posted by TubaMorg

Hope this doesn't happen to us! So have you tested to make sure they are getting power (12v)? What I really dig about them is that you can trouble shoot them whether they are plugged into the RC or not, all you need is the 12 volts. The red LED on the back of the Receiver lights up when active, but I'm guessing you already know all this.

Random thought, isn't there some way to actually 'see' the IR light?

COLOR=DarkSlateBlue]Use your digital camera to 'SEE' IR wavelength !!!

IR led should appear lighted depending on your camera's sensor and lens'

Silicon sensors are responsive to ~800-950nm of IR LED's.

Check out this trick on your IR TV / VCR remote.....
Note that pulsed IR leds will be fainter due to lower averabe energy.

My Panasonic VCR & Oly Digital camera easily 'saw' illumination from the 40Khz pulsed field LED's used in 2003 (field side/loc to hit pedastal ball(s) release to release overhead balls in autonomous

I posted pict w/IR emitter illuminated in the CD photo gallery (2003?)
or email me requesting same...

Dale(294engr][/color]


Like some special goggles or something?

Another thing to check (after you verify your sensors actually have power): There are sensitivity pots that can be fiddled with depending on the application. If you are using a "broken beam" type of scenario, the sensitivity can be dialed down, but if you are using reflected IR (like we are) then you have to turn it up. Establish the conditions that should turn your sensors on, then turn the pots until the red light appears.

If none of that works, then I guess you have to get new ones (you would have to get them from the supplier). Isn't it strange how you can load a perfectly good robot in a crate then two weeks later open it up and pull out a broken one? Seems to happen over and over again

Dale(294engr]