Getting Fancy with Sensors

[FadyS.]

Hi, we're a rookie team and we're not done autonomous mode, but since we have over 3 weeks until our regional, I'm taking the time to work on autonomous mode. Now, I don't want to go overboard with sensors for autonomous but I want to know what kind of stuff is available at a local Radioshack that may be useful to autonomous. I already picked up a few switches and a potentiometer. I may pick up another potentiometer though. Also, I might pick up a few infrared phototransistors. Are these analog or digial sensors? Any other neat gizmos to pick up? I've got to admit, I love playing around with all these sensors. Hehe, "Captain, sensors are picking up a spatial anomoly! We should shut down the warp drive!!!" lol.

[ejthe4th]

our team is using a whole load of sensors for auton_mode =1. one of the first sensors we used is the banner light sensors. they came standard in the kit, they give off a digital signal.

their wiring schematic is on page 18 of section 5 "The Robot". the Blue wire goes to ground, Brown goes to +12V (from a 20Amp breaker on the fuse bus, it does not connect to the +5V on the robot controller). the black and white wires are the signal wires, one is NC (normally closed) and the other is NO (normally open) there is a schematic on the side of the sensor that helps explain it. you should only need to hook up one of the black or white wires, not both (it's your pick). these sensors can tell the difference between light and dark, it will either "see" a light or it won't, nothing between (good for line following to finding a line)

have you tried using the current sensors that are provided in the kit? we've had quite a bit of "fun" testing these...we wanted to know how many amps the motors could pull, so we put the 'bot agains the wall, i climbed on and we went "full speed ahead", the motors got really hot, the wheels slowly spun, burning 2 tread marks into our school's carpeting, and pulling 40 amps per motor...we only tested this once.

if you need any help with these i'll try and help, just e-mail me

[JamesWu]

hahaha... I wish I could have seen it. A Robotics dude climbing onto his poor robot and getting ready to hangon for a wild ride but instead recieving some burnout.

[KenWittlief]

Personally I think the most usefull one you can get is the gyro sensor, it will allowyou to measure if your bot is turning, or how much its turning, or how far its actully turned

I cant imagine doing auton mode without it - most bots, if you turn the motors on, they drift to one side or another, and when you turn its hard to dead recon to a new heading

the gyro resolves all those problems with excellent accuracy

only thing is, its not a simple device to use - but if you have 3 weeks you can get one and play with it on your EDU bot - the best source I found is Avent (electronics distributor) - they had them in stock last time I checked for $50

search on 'gyro' or 'yaw rate' here in CD and you will find several threads on the subject, and how to use them - I think the part number (top of my head) is ADRSX150EB- something like that - its in the other threads.

[deltacoder1020]

a small note, apparently the banner sensors distributed in this year's KOP do not have the schematic on the side... last year's did.

[Astronouth7303]

Yes, And this year's aparently have a better range (Ask Biff).

You pulled only 40 amps? We manged to pull 140.

[FadyS.]

Originally Posted by Astronouth7303

Yes, And this year's aparently have a better range (Ask Biff).

You pulled only 40 amps? We manged to pull 140.

Also, anyone know where we can get encoders? What kind of stores do we check at. Also, we do we get extra infrared sensors from? The infrared phototransistors have terrible range.

[deltacoder1020]

Digi-Key sells encoders, you could check with them (chances are Radioshack doesn't have them in stock )

[jamapor]

We are using an extreme amount of sensors. We have ultra-sonic sensors in the front bumper of our robot to detect distance to the stairs. Then, we have two gyro's to detect X motion as well as Z direction motion. Also, we have light sensor, wheel-encoders to count wheel rotations to sense distance traveled. We have numerous potentiometers and countless limit switches. (over 15). Sensors can be very usefull this year.

[Ryan M.]

Our robot is really fairly light on the sensor side. We have some to prevent damaging certain components, but the only other things that we have are two encoders on the wheels. I wish we had more...

I hope that next year they'll let me use the gyros. They'll be much more fun than counting ticks on a stupid encoder.

[Astronouth7303]

ick up jaw: You have space left for anything? I'm not sure the RC has that many ports on it!

[Random Dude]

Originally Posted by Astronouth7303

ick up jaw: You have space left for anything? I'm not sure the RC has that many ports on it!

Well, they could be using an external micro for the sensor IO. Thats how I'd do it atleast.. collect and process all the data externally, and just ship it back in a nice neat format to the RC.

That way you don't need to waste cycles on the RC integrating the gyros, and counting the encoders, etc...

[KevinB]

Originally Posted by Texan

I hope that next year they'll let me use the gyros. They'll be much more fun than counting ticks on a stupid encoder.

We're having great success with "counting ticks on a stupid encoder".

[jacob_dilles]

Originally Posted by KevinB

We're having great success with "counting ticks on a stupid encoder".

not only did we have great sucess, but we can control turning, distance and speed down to 1/4", and its shorter, faster, and simpler then writing a gyrp algortiom. 2 intrupts, 2 banner sesors, 2 wheels, 2 variables. lol thats it.

Originally Posted by Random Dude

Well, they could be using an external micro for the sensor IO. Thats how I'd do it atleast.. collect and process all the data externally, and just ship it back in a nice neat format to the RC.
That way you don't need to waste cycles on the RC integrating the gyros, and counting the encoders, etc...

for next year im working right now on a pic16F84 in basic (yea i know; shush up) to integrate the gyros (2x) 2 banner sensors (for the wheels) and a compass. it will output the data in rs232 format as (speed)-(direction) every time its polled, and a (time)-(distance) may get built it soon. i might might write a white paper on it if i can pass history

edit: once agein, my education is interfering with my schooling

[Ryan M.]

Yeah, it works fine, I just don't like them because of the relative unreliabilty of them. For instance, it's impossible for us to autonomously make it up onto the platform and turn toward the bar because we bounce some. At least with gyros, they don't mess up if a wheel slips or you get hit from the side or something like that.

Anyway, encoders do work.