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Asked — Edited

Edge Detectors

I'm a newbie to the forum and just in the planning stage ( and gathering parts) for the OmniBot conversion. D.J. calls for a QR111D edge detectors. I can"t seem to find one online. Anyone know if there is an equivilent part (w/part number) available? Will any of the detectors from solorbotics work?
Thanks in advance.


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Hey Lostcreekstation Welcome to the forums! I hope you can find losts of help and hints here.

I believe DJ probably ment this sensor which is called the QRD1114 and is available at Solarbotics, hope that helps!

Could you use that sensor as a cheap version for a IR range sensor?
I'm looking for a cheap range sensor... Weird enough my ez-b gets a time-out when I try to use a pingsensor in ARC even when it's not connected... And that doesn't happen with IR sensor so I'd figure that's the way to go.
The IR sensor won't give you a very high resolution. Which ultrasonic ping sensor are you using? And by time-out, do you mean the EZ-B disconnects when you attempt to use it?

the QRD1114 isn't a very strong IR. You can get about 2-3 inches of range with it, if you use a very sensitive resistor. I forgot what value I used. I played with a few and tried a variety of ranges.

Here's a great link on the QRD1114 schematic and datasheet: QRd1114 IR Sensor Schematic
I get the time out when I atempt to use a ping sensor.
The blue led turns off and I get:

Comm Err: The operation has timed out. (Expect Response: True, Rcv: 0)

I think it's still connected as the red led of the bluetooth module isn't blinking,
it's solid when it happens. Also I'm using a HC-SR04, but I get the time out even
when it's not pluged in...

Oh while I'm at it, since the last update, the 2011.10.26.00 release. With every
script I start I get:

Script Error: Index was outside the bounds of the array.

I also get it when the script stops, but strangly enough everything is working just
fine, except for the ping sensor. Befor the update I didn't get that error and I'm
still using the same script.

A peace of script:

My robot is functioning as I wanted it to, so... I'm doing somthing wrong or is it a
bug of some sort.
Interesting... Very very interesting. I can't really understand why that would happen. Since v13 is a complete re-write of the firmware, maybe it will work for you again *shrug*

Do the pins that the HC-SR04 was plugged into work? Have you tried configuring other pins for the HC-SR04 and see if it still disconnects? Maybe there is a short on the board for those 2 pins, or one of them. I'm not really sure! That's an interesting one.

As for the script error. I've never seen that and it doesn't give me that error with my version. But my version is for v13, so I can't try it with the old one because I no longer have it.

As of tomorrow, those troubles I guess will be resolved:)

IT's all fixed!!
From now on I will worship you like a GOD, it's even working better than before.
Eventhough I had to re-write all my scripts it was definitly worth it!
The ping sensor works and I'am not getting any script errors anymore!

You even fixed the problem that if I moved the stick of a joy-stick diagonal that
my motors kept running and wouldn't stop anymore. But now it does!

Thanks DJ, the update fixed everything and made the things I had work better.
:) I'm very glad you like it! You really make me smile dude!
Bringing this back onto the edge detector topic. Am I right in assuming mounting one of these on the front, facing down would be used to make sure I don't drive down the stairs by accident? (basically, have a script that stops moving forward or stops and turns when the sensor CAN'T see anything)?

My family room is one step down from the kitchen. If my wife will let me, I will put a ramp on one side of the opening for the bot, but I need to make sure he only uses the ramp and doesn't fall down the step (unless I design some kind of self-righting mechanism, but that will probably come late in the build if at all).

hey @thetechguru

Yep thats the basic idea i believe. Below is something DJ wrote in another topic.

"On my Wall-E, I used a sharp IR distance sensor (the same type you are using) pointing down on an angle.

During initialization, i get the value of the IR sensor. If the value changes within a determined percentage, I backup and turn around. This helps for both raised and lowered surfaces."
Thanks both. Thegoodrobot, you just exemplified the ddifference between an engineer and a technician. I was looking to engineer an elegent solution, and you provided a simple practical one that will work perfectly well.

@thetechguru he mounted a sr04 facing down right? So this confirms it works?

I don't see any reason why this would not work. You just need to ensure you have the sensor overhanging enough which may/may-not work. Are you using your RAD track base or the Omnibot wheel base? I am looking at my RAD 2.0 base and you could easily mount one in front of the cup sensor facing the floor and any drop would likley be seen before your bot went over the edge. Problem will be seen when you approach the drop off from an angle...unless you have multiple sensors (an option...one on each corner). Tracks will generally an advantage over wheels as you can 'go over the edge' with the tracks a bit and still pull back.


@kkeast I planned on mounting it under the base , currently using Omnibot base to get things going , I was going to mount underneath but with about a 30-45 degree angle forward so that it should detect a cliff about 6 inches before the front wheels. I have the one.sr04 that came with.the kit and bought 3 more on ebay which should be here anytime this week. So I will have a total of 4. So I could have one radar , a front cliff sensor , a back up/ cliff sensor , and maybe I would use.the last one for to avoid tables. Always any suggestions.of what to.do with.my 4 sensors is greatly appreciates:)
soooo.......what sensors are we going with for edge detection?