Go to Post I love the smell of burning silicon in the morning. - Al Skierkiewicz [more]
Home
Go Back   Chief Delphi > Technical > Programming
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 03-03-2004, 11:35
gnormhurst's Avatar
gnormhurst gnormhurst is offline
Norm Hurst
AKA: gnorm
#0381 (The Tornadoes)
Team Role: Programmer
 
Join Date: Jan 2004
Location: Trenton, NJ
Posts: 138
gnormhurst will become famous soon enoughgnormhurst will become famous soon enough
Why not analog sensors??

I am frustrated by the nearly exclusive use of digital sensors in the kit -- sensors that output either 1 or 0. The Banner sensors are like that, and the IR sensors in the trackers are like that. Why not analog?

Some may think that "1" or "0" is a much cleaner, noise-free signal than an analog signal, but it is nearly information-free as well!

I know one team used constant tracker hunting to get a better idea of the direction of the IR, and that is a great solution given one-bit sensors. But if each tracker's IR sensor put out an analog value proportional to the "brightness" of the IR it was seeing, then small pointing errors could be determined as the difference between the values, without having to hunt back and forth with the servo. Integrate the sensor difference and apply to the servo -- or something like that.

If two analog line sensors were pointed, "defocused", at the left and right edges of the line such that the output was a measure of how far off the edge the sensor was, then, again, the small error signal would be the difference of the sensors. Negative means "too far left", positive means "too far right", and zero means right on.

Yes, the outputs would have some noise in them -- that's part of the fun, filtering out the noise.

I think part of the reason that the gyro approach works well is that it gives an analog measure of the error.

Comments anyone?
  #2   Spotlight this post!  
Unread 03-03-2004, 11:43
Kevin Karan's Avatar
Kevin Karan Kevin Karan is offline
Linux Guy
AKA: maxdamage
None #0174 (Arctic Warriors)
Team Role: Alumni
 
Join Date: Jan 2003
Location: Liverpool, NY
Posts: 141
Kevin Karan will become famous soon enoughKevin Karan will become famous soon enough
Send a message via AIM to Kevin Karan
Re: Why not analog sensors??

Quote:
Originally Posted by gnormhurst
"1" or "0" is a much cleaner, noise-free signal than an analog signal
Thats good enough for me
__________________
It isnt ALWAYS the programmers falt!
2004: Buckeye team website award
2002: Rutgers semi-finalists
2001: National semi-finalists
2001: Rutgers semi-finalists
1998: Manchester Rookie All-Star Award
  #3   Spotlight this post!  
Unread 03-03-2004, 11:50
Dave Flowerday Dave Flowerday is offline
Software Engineer
VRC #0111 (Wildstang)
Team Role: Engineer
 
Join Date: Feb 2002
Rookie Year: 1995
Location: North Barrington, IL
Posts: 1,366
Dave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond reputeDave Flowerday has a reputation beyond repute
Re: Why not analog sensors??

Quote:
Originally Posted by gnormhurst
But if each tracker's IR sensor put out an analog value proportional to the "brightness" of the IR it was seeing, then small pointing errors could be determined as the difference between the values, without having to hunt back and forth with the servo. Integrate the sensor difference and apply to the servo -- or something like that.
Except that brightness would also vary by the distance your robot is from the beacon. So, if you read a value of 120 from your analog light sensor, does that mean you're pointed right at it but 20 feet away, or does it mean you're right next to it, but pointed 45 degress away from it?
Quote:
If two analog line sensors were pointed, "defocused", at the left and right edges of the line such that the output was a measure of how far off the edge the sensor was, then, again, the small error signal would be the difference of the sensors. Negative means "too far left", positive means "too far right", and zero means right on.
Do such sensors exist? If they do, you could always buy them as a custom electronic component and use it - you're not limited to just the sensors provided in the kit. I'd be a little surprised if something like this really exists, though (at least something that would work for this application).
  #4   Spotlight this post!  
Unread 03-03-2004, 11:50
FotoPlasma FotoPlasma is offline
\: |
no team
 
Join Date: Jul 2001
Rookie Year: 2001
Location: San Jose
Posts: 1,900
FotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond reputeFotoPlasma has a reputation beyond repute
Send a message via AIM to FotoPlasma
Re: Why not analog sensors??

For the most part, regarding the kit, FIRST operates on a two-part plan: 1) what's cheap, and 2) what's free. Maybe it was neither to acquire analog sensors which perform the same functions as the digital sensors we received. If you want to use analog sensors, you can, but I don't see any reason why you should be complaining about what was provided in the kit.

It's not like FIRST is getting kickbacks from the digital sensors industry...
__________________
I played hacky sack with Andy Baker.

2001-2004: Team 258, The Sea Dawgs
2005: Team 1693, The Robo Lobos
  #5   Spotlight this post!  
Unread 03-03-2004, 11:57
deltacoder1020's Avatar
deltacoder1020 deltacoder1020 is offline
Computer Guy
AKA: Dav
#1020 (The Indiana Prank Monkeys)
Team Role: Programmer
 
Join Date: Jan 2004
Location: Muncie, Indiana
Posts: 340
deltacoder1020 has a spectacular aura aboutdeltacoder1020 has a spectacular aura about
Send a message via AIM to deltacoder1020
Re: Why not analog sensors??

digital sensors are also easier for novice teams to use, whereas analog sensors are harder to implement algorithms for. there's no restriction on getting more complicated sensors, but FIRST also probably wants to provide newer, more inexperienced teams with things that are simple to use.

the cheap/free argument is also quite valid.
__________________
Team 1020, the Indiana Prank Monkeys (www.team1020.org)
  #6   Spotlight this post!  
Unread 03-03-2004, 12:26
Kevin Watson's Avatar
Kevin Watson Kevin Watson is offline
La Caņada High School
FRC #2429
Team Role: Mentor
 
Join Date: Jan 2002
Rookie Year: 2001
Location: La Caņada, California
Posts: 1,335
Kevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond reputeKevin Watson has a reputation beyond repute
Re: Why not analog sensors??

Quote:
Originally Posted by gnormhurst
I am frustrated by the nearly exclusive use of digital sensors in the kit -- sensors that output either 1 or 0. The Banner sensors are like that, and the IR sensors in the trackers are like that. Why not analog?
You're free to sample the ones and zeros with an A/D as they zip in .


Quote:
Originally Posted by gnormhurst
Some may think that "1" or "0" is a much cleaner, noise-free signal than an analog signal, but it is nearly information-free as well!
You're kidding, right?


Quote:
Originally Posted by gnormhurst
...But if each tracker's IR sensor put out an analog value proportional to the "brightness" of the IR it was seeing, then small pointing errors could be determined as the difference between the values, without having to hunt back and forth with the servo. Integrate the sensor difference and apply to the servo -- or something like that.
How would you discriminate against all of the other sources of 940nm infrared? Would you use a different wavelength for the other beacon?


Quote:
Originally Posted by gnormhurst
If two analog line sensors were pointed, "defocused", at the left and right edges of the line such that the output was a measure of how far off the edge the sensor was, then, again, the small error signal would be the difference of the sensors. Negative means "too far left", positive means "too far right", and zero means right on.
There's nothing preventing you from doing this. Radio Shack carries infrared phototransistors.


Quote:
Originally Posted by gnormhurst
Yes, the outputs would have some noise in them -- that's part of the fun, filtering out the noise.
*sigh*

-Kevin
__________________
Kevin Watson
Engineer at stealth-mode startup
http://kevin.org
  #7   Spotlight this post!  
Unread 05-03-2004, 18:58
gnormhurst's Avatar
gnormhurst gnormhurst is offline
Norm Hurst
AKA: gnorm
#0381 (The Tornadoes)
Team Role: Programmer
 
Join Date: Jan 2004
Location: Trenton, NJ
Posts: 138
gnormhurst will become famous soon enoughgnormhurst will become famous soon enough
Re: Why not analog sensors??

Quote:
Originally Posted by Kevin Watson

Quote:
Originally Posted by gnormhurst
Some may think that "1" or "0" is a much cleaner, noise-free signal than an analog signal, but it is nearly information-free as well!

You're kidding, right?

Not at all, I was thinking "information theoretically". One bit is the smallest amount of information. 10 bits is a lot more. Now, it also depends on bandwidth and noise, and if the one-bit case is fast enough, you can get a lot of information.


Quote:
How would you discriminate against all of the other sources of 940nm infrared? Would you use a different wavelength for the other beacon?
I was thinking of using, say, a 40 kHz beacon (CW, not pulsed) and have another frequency for the other beacon, say, 33 kHz. The rub is that to implement the dual-tracker system I think you would need eight sensors instead of four (four for each beacon frequency). $$$


Quote:
There's nothing preventing you from doing this. Radio Shack carries infrared phototransistors.
Lack of time prevents me, at least in a 6-week build cycle. Maybe I can play with this in the off season. sigh....



BTW, I'm here at the regional in Trenton, NJ, and when I asked which beacon was "1" and which beacon was "0", I got some pretty blank looks. I said, "You know, the IR beacons for IR tracking?" More blank looks. They found someone from IFI who made a few calls and learned that "this" beacon is connected to pwm01 and "that" one is on pwm02.

But I still can't get it to work. Tomorrow we will have our test beacons, so maybe we can get some answers. It's pretty hard to debug with only one run every 90 minutes, with no telemetry, just observing the robot from the stands about 200 feet away!


Quote:
*sigh*
Exactly.


-Norm

Last edited by gnormhurst : 05-03-2004 at 19:11.
  #8   Spotlight this post!  
Unread 05-03-2004, 19:08
gnormhurst's Avatar
gnormhurst gnormhurst is offline
Norm Hurst
AKA: gnorm
#0381 (The Tornadoes)
Team Role: Programmer
 
Join Date: Jan 2004
Location: Trenton, NJ
Posts: 138
gnormhurst will become famous soon enoughgnormhurst will become famous soon enough
Re: Why not analog sensors??

Quote:
Originally Posted by Dave Flowerday
Except that brightness would also vary by the distance your robot is from the beacon. So, if you read a value of 120 from your analog light sensor, does that mean you're pointed right at it but 20 feet away, or does it mean you're right next to it, but pointed 45 degress away from it?

You would need two sensors (just like Kevin's tracker setup). The ratio of the difference to the sum (left-right)/(left+right) would indicate the off-angle-ness: if they have equal outputs, it's pointed straight; if the left is larger, it's pointed right; right larger means pointed left.

Or something like that.
Quote:
Do such sensors exist?
Dunno. I imagine that the internal processing of the sensors in the kit generates the signal I want. And then they run it through some threshold to throw away most of the information(!) and output a 1 or 0.

Last edited by gnormhurst : 05-03-2004 at 19:24.
  #9   Spotlight this post!  
Unread 05-03-2004, 20:52
Greg's Avatar
Greg Greg is offline
Registered User
FRC #1075 (Sinclair Sprockets)
Team Role: College Student
 
Join Date: Nov 2002
Rookie Year: 2003
Location: Whitby, Ontario, Canada
Posts: 108
Greg is on a distinguished road
Send a message via ICQ to Greg Send a message via MSN to Greg
Re: Why not analog sensors??

The IR sensors are used because they are standard and readily available. All IR receivers in home electronics equipment are (almost) identical to these. They have quite a lot of circuitry in them (they just look small ) so they filter out the noise and decode the binary signal. In my opinion these sensors are much more reliable than those that would depend on brightness. What if someone takes a picture during autonomous?
  #10   Spotlight this post!  
Unread 05-03-2004, 21:12
galewind's Avatar
galewind galewind is offline
... more like a temperate breeze
AKA: Chris Gregory
FRC #1089 (Team Mercury)
Team Role: Teacher
 
Join Date: Jan 2003
Rookie Year: 2003
Location: Hightstown, NJ
Posts: 410
galewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond reputegalewind has a reputation beyond repute
Send a message via AIM to galewind
Re: Why not analog sensors??

Quote:
Originally Posted by gnormhurst
Some may think that "1" or "0" is a much cleaner, noise-free signal than an analog signal, but it is nearly information-free as well!

Comments anyone?
I personally believe that "Yes" or "No" is sometimes better and much more useful than "well, MAYBE, but, well, I can't REALLY tell, it's kinda sorta"...

using two digital sensors is, in tandem, rediculously useful. Think about your eyes -- look at an object... if you close your left eye and can see it, check your right eye -- if your right eye can't see it, you need to turn left...
when you can turn left and see it, and you can see it with both eyes, it's in front of you....

once one eye loses sight, re-evaluate and adjust.
__________________
Chris G
Advisor, Team Mercury (1089), Hightstown High School
  #11   Spotlight this post!  
Unread 06-03-2004, 19:14
Greg McCoy's Avatar
Greg McCoy Greg McCoy is offline
boiler up!
FRC #3940 (CyberTooth)
Team Role: Engineer
 
Join Date: Feb 2002
Rookie Year: 2002
Location: Kokomo, IN
Posts: 484
Greg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond reputeGreg McCoy has a reputation beyond repute
Send a message via AIM to Greg McCoy
Re: Why not analog sensors??

I'm not sure what the point of this discussion is

Sensor choice obviously depends on the application, and I think that FIRST lets you use just about anything you want. In the kit, well, FIRST gives us what they give us, and from what I've seen it's decent stuff that is pretty easy to use. Beyond that, as long the sensors you want to use are legal, then use them
  #12   Spotlight this post!  
Unread 06-03-2004, 20:24
Astronouth7303's Avatar
Astronouth7303 Astronouth7303 is offline
Why did I come back?
AKA: Jamie Bliss
FRC #4967 (That ONE Team)
Team Role: Mentor
 
Join Date: Jan 2004
Rookie Year: 2004
Location: Grand Rapids, MI
Posts: 2,071
Astronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud ofAstronouth7303 has much to be proud of
Re: Why not analog sensors??

Sometimes Digital makes sense (Encoders, bumpers, IR finding) and sometimes it doesn't (Position, Air Pressure, current). Basically, you ask "Do I need 1024+ values, or do I just need to calibrate and have a above/below return?"
  #13   Spotlight this post!  
Unread 07-03-2004, 08:50
Ryan M. Ryan M. is offline
Programming User
FRC #1317 (Digital Fusion)
Team Role: Programmer
 
Join Date: Jan 2004
Rookie Year: 2004
Location: Ohio
Posts: 1,508
Ryan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud ofRyan M. has much to be proud of
Re: Why not analog sensors??

As has already been said indirectly several times, what's wrong with a simple signal with a simple algorithm? Sure, it's really fun to make a complex algorithm that works, but in the real world, the simpler things are, the less likely they are to fail and the easier they are to maintain.

Linux is an example of this. It gives you complete power; you can delete anything, access kernel memory, change kernel memory, etc. It lets you do anything, but if you don't know what you are doing, you can easily break it. (assuming, of course you are admin; users are a different story.) Windows on the other hand, doesn't let you do that. It pretty much protects you from stuff that you can do to break it. (It lets itself break itself, but again, another story) The banner sensor are the same way; you don't have as much power, but they protect you from interference from anything other than what you actually want.
__________________


Last edited by Ryan M. : 07-03-2004 at 08:56.
  #14   Spotlight this post!  
Unread 07-03-2004, 11:03
steven114 steven114 is offline
Programming Wizard and Team Captain
AKA: Steven Schlansker
FRC #0114 (Eaglestrike)
Team Role: Programmer
 
Join Date: Feb 2004
Location: Los Altos, CA
Posts: 335
steven114 is a jewel in the roughsteven114 is a jewel in the roughsteven114 is a jewel in the rough
Send a message via AIM to steven114
Re: Why not analog sensors??

The irony of your analogy, Texan, is that it's a lot easier to bring down a Windows machine than it is a Linux machine (assuming non-root accounts on both sides, of course)
  #15   Spotlight this post!  
Unread 07-03-2004, 11:34
Adam Y.'s Avatar
Adam Y. Adam Y. is offline
Adam Y.
no team (?????)
 
Join Date: Mar 2002
Location: Long Island
Posts: 1,979
Adam Y. is a splendid one to beholdAdam Y. is a splendid one to beholdAdam Y. is a splendid one to beholdAdam Y. is a splendid one to beholdAdam Y. is a splendid one to beholdAdam Y. is a splendid one to beholdAdam Y. is a splendid one to behold
Send a message via AIM to Adam Y.
Re: Why not analog sensors??

Quote:
using two digital sensors is, in tandem, rediculously useful. Think about your eyes -- look at an object... if you close your left eye and can see it, check your right eye -- if your right eye can't see it, you need to turn left...
Errrrr.... That is nice and all but your eyes resemble analog sensors more than digital. Also your analogy starts to break down when you actually think of the consequences when you loose an eye. You pretty much loose any ability to tell depth. Anyway the rules pretty much prevent the use of most if not all decent analog sensors.
__________________
If either a public officer or any one else saw a person attempting to cross a bridge which had been ascertained to be unsafe, and there were no time to warn him of his danger, they might seize him and turn him back without any real infringement of his liberty; for liberty consists in doing what one desires, and he does not desire to fall into the river. -Mill

Last edited by Adam Y. : 07-03-2004 at 11:36.
Closed Thread


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Interrupts and rotation sensors kor Programming 3 12-02-2004 11:05
Harmful side effects with current sensors m0rph3us Electrical 2 11-02-2004 07:31
wiring diagram for light sensors??? pagemauck Control System 1 21-01-2004 16:32
what type of sensors are good and convenient magical hands Programming 7 04-01-2004 23:04
Q&A Discuss: Optical sensors with EduBot CD47-Bot Extra Discussion 2 01-03-2003 18:37


All times are GMT -5. The time now is 01:30.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi