What Kind Of Sensor Do I Need

Question

I want to put a sensor on a robot to keep it from running off the table or down a flight of stairs. Something that can sense the drop off. What do I need for this? is there a way to configure an Ultrasonic sensor to do this? Thanks

Dunning-Kruger · Answer

@Bob... This is what I use for that... IR Detector This will work too (depending on how low to the ground your bot is)... Basically an off/on analog switch... Short range IR sensor These would use the analog ports and are easy to use... Roombas use this kind of sensor too to keep from falling down stairs...

thetechguru · Answer

Others have used a sharp IR sensor for this. I just mounted one to the front of my Roli, but I haven't written the script needed yet. The Sharp Distance Sensor ARC object stops the movement when you get too close to something rather than when you get too far from it, so unless DJ can add an object, we'll need a script to monitor the ADC port and over-ride the movement panel or movement script(s) when it senses a drop-off. A ping sensor would probably work, but I think the IR sensors are more sensitive to close objects. Alan

CochranRobotics · Answer

I use ir detectors for my wall-e pointing down. The type of sensor only depends on the distance you need to measure. An IR sensor will measure short distances really well (a couple of inches) where a Ultrasonic sensor will measure a few feet. Also, the sensor you pickup for this could go further or shorter depending on the brand of the sensor. Ultrasonic isnt as good for really close up (a few inches) for the most part.

Jeremie · Answer

An OPB704 is an ideal sensor for that application but it does require a couple external resistors to be added in order to work well with the ez-b. There should be a few application circuits floating around the intertubes, but it's a common reflective sensor for robotics. edit: It's best to hook up to an analog port just like the sharp sensors

bhouston · Answer

Wow ! You guys are quick! An IR sensor it is then. Thanks

robo rad · Answer

Since my Large Terminator will be as tall as me soon , I have ordered 1 more Ultrasonic sensor and the arc sweeping mini servo along with a 150 cm maximum distance Sharp I.R. sensor to place up and down the front of the Terminator for a total of 3 and one at the back along with bump switches just in case. Will the Sharp sensor still need any added resistors as Jeremy mentioned back in 2015? Also Will ARC work with all versions of Sharp I.R.?

Jeremie · Answer

Hi @Robo Rad, the OPB704 is a different kind of reflective infrared sensor, so it needs some resistors to be added to make it function. If you are using Sharp infrared distance sensors no external circuitry is needed, as it's all built-in. The only thing you need to worry about with Sharp sensors is that they need to be powered by 5V for ideal operation. The output is from 0-2.5V I believe. It would work in ARC just fine. You just need to attach them to an Analog port on your ARC compatible controller.

robo rad · Answer

Good to know Jer, I am just now pulling out the older EZB V3 as it makes a decent 5 volt regulator for all my sensors and it looks impressive with the blue heart beat L.E.D. and red bluetooth blinker going!

thetechguru · Answer

I doubt you need the scripting help, but if you want an example of using the IR sensor for edge detection, you can download my MyRoli mkiii project. It has an edge detection script. You can't just use the IR distance object because it assumes you want to stop when you get close, but for edge detection, you want to stop and reverse when the distance increases.

Alan

Alan · Answer

@robo rad - interesting fact that not many know, the blue heart beat L.E.D of the EZ-B V3 was based on my pulse! It was DJ's idea to make it appear more natural.  Cool you still have one!

Dave Schulpius · Answer

Hey! What happened to Alan?! At least the heartbeat of EZ Robot didn't disappear when Alan did.

Jeremie · Answer

Which Alan are you referring to, Dave? Lol Back to back Alans posted to this thread

robo rad · Answer

Ha right on Alan, I did actually read somewhere before that people were calling the Blue light a heart beat and that stuck in my head as it really does seem to be a living pulse. Yes I still love the EZ-3 and continue to use along with the EZ-4.:)

bhouston

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