Is there a way to use a phototransistor and IR with the Boe Bot for object avoi

Microcontrolled

I have a Boe Bot that I have used for years and have used the Wiskers, photoresistors, and infared. I, however, lost one of the IR LEDs. As a replacement, I just bought a phototransistor and IR led as a replacement (I just bought it at radio shack, I didn't order it )
I would use my other detector, but the IR led is not set at the same wavelength (980nm). So I was wandering if there was a·way to use the phototrasistor as the detector for the for the IR, that can work with the Boe-Bot.

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Thank You For Reading! Please Respond!!!

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Mike Green

Have you tried it? 980nm is less than a 5% difference from 940nm which is the peak sensitivity frequency of the IR emitter and detector sold by Parallax. If you download and look at the datasheet for the IR detector, you'll see that its sensitivity at 980nm is only 90% of that at 940nm, not enough to make a practical difference.

Microcontrolled

I have tried it. It dosn't work. I ran the sample IR test program inside the "Robotics with the Boe-Bot" textbook and it did not detect anything. If it matters, this inparticular IR LED has a blue tint to it, but I don't think it matters.

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Thank You For Reading! Please Respond!!!

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Mike Green

There must be something else about your setup. If you have a digital camera with an LCD viewscreen, you should be able to use it as an IR detector. If the IR emitter is on, you should be able to see it in the viewscreen.

Make sure you have it wired up correctly.

Franklin

Are you sure it is an IR led? Might be UV.

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- Stephen

Chris Savage

...or you may have wired up the phototransistor/photodiode instead of the LED.

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Chris Savage
Parallax Engineering

erco

I use Radio Shack parts, and I have seen phototransistors with the wires switched. That is, the long (+) and short (-) wires reversed. The Shack gets huge bulk buys on out-of-spec items sometimes, so you need to be careful. Sounds like the pack you bought is the "matched" set, one IR LED (usually blue tint) and one IR phototransistor (usually clear). Just to be safe, try both items in both polarity directions: hook them up through a 220 ohm resistor to 5 volts and make sure you're getting ~15 mA current.

The phototransistor should be dramatically more sensitive to light as tested with a multimeter. Set a multimeter on its highest resistance range setting, and hook its leads to the ptx (again, try both directions). When you point the ptx at a light source, the resistance should drop significantly.

As ever, Mike is right; you should be able to see the emitted IR through a camera viewfinder. If not, there is always the possibility that the LED is bad or that you may have damaged it accidentally. Even a brief connection to direct 5 volts can release the magic smoke inside.

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·"If you build it, they will come."

Microcontrolled

I am using a IR LED. It DID come in a "matched" set from Radio Shack complete with the phototransistor and IR led. I will try the digital camera trick to see if the IR led is working, however I forgot to mention that I also puchesed two other IR leds with the same ratings as the one in the kit and they did not work. I am not powering it with 5V, but with the FREQOUT command on the robot as the book instucts you to do with the included IR LED. I have the connections the same as the book says to do with the included hardware, excluding the Vss pin on the detector. I have the positive end of the detector hooked up to 5V DC and the negitive end hooked up to one of the I/O pins. The LEDs are not clouded or show any outward sign of being broken, but I will check.

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Thank You For Reading! Please Respond!!!

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erco

Hard to believe that you got 3 bad LEDs. I suspect something else is amiss. If·you·sketch up a diagram of your exact circuit, LED and 3-pin detector, we can help you more directly. If possible,·attach a·clear photo of your breadboard circuit, and attach your code. AND, the exact circuit you are trying to replicate; either a link or book & page reference.

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·"If you build it, they will come."

MovieMaker

The problem in my home is that all of the florescent bulbs give off the same frequency and confuse the dang thing. I have NOT tried pulse modulated yet. But, this may be your problem. Those energy saving bulbs are bad about interference with our project. I have even thought about going microwave. But, it was said on the sight it can only see about 16 feet away.