Help with christmas project! - photoresistors

emmali55 · 2008-12-19 22:21

Hi, I am trying to program·a boe-bot as a chrstmas surprise.· I would like it to be sitting in a dark room and move forward when the light is turned on.

I don't have much experience with this kind of stuff, but in using the book (Robotics with the Boe-Bot) I was able to program it to "wander towards the light."· If the shadow on the left resistor is more than the shadow on the right, it turns Right, etc.· If shadows are equal it drives straight.·

This is good, but in the dark it just pulses in circles.· Can someone please clue me in to a code that translates: "If·level of shadow is certain number (i.e all dark/no light)·sit still; if light, move forward."

It would be wonderful if I could make this happen before Christmas, I am pretty excited about it.· If you think you can help please let me know! [noparse]:)[/noparse]

Mike Green · 2008-12-19 22:35

The BoeBot code for wandering uses the RCTIME statement to read the value of the photoresistor. This value goes up in the dark. You just need to experiment to see what the value is for the darkness level you want. If both photoresistor values are greater than this number, then your program should do a SLEEP for a short time (like a second or so), then go back and check the photoresistors again.

If you can't figure this out, post your source program as an attachment to your reply.

SRLM · 2008-12-19 23:15

Let me guess: present delivery system? If so, you could get some longer screws, some small tubing, and a piece of wood to make a nice little platform on top.

GeorgeL · 2008-12-20 06:03

"Let me guess: present delivery system? " Thats Santas job...dont steal it. On the other hand a quick and durty solution, calculate some values and do a IF THEN ELSE ENDIF type deal.

emmali55 · 2008-12-20 16:37

Thanks for your help. present delivery system: how did you guess!? I plan on pulling a little rolly cart, holding the present, behind the BoeBot. It is just a video game so it won't be too heavy. I also have an LCD Screen programmed to scroll a little message. This is all new ot me so I am just anxious to get it all together!

Mike Green: I like the idea of SLEEP. How would I use it? A combo of GeorgeL's idea with IF THEN ELSE ENDIF?
Such as:

IF light levels (or shadow levels, i suppose?) are xxxx
THEN SLEEP
ELSE drive straight
ENDIF
?

I will post what I have, like you suggested. Maybe that will help. I don't entirely understand which values stand for what. (i.e. FREQOUT 4,2000,3000) so please keep that in mind. [noparse]:)[/noparse] I'm pretty sure what I need to make changes to will be under the "Navigate" heading?

Here is a what I have so far:

DEBUG "Program Running!"
timeLeft VAR Word
timeRight VAR Word
average VAR Word
difference VAR Word

FREQOUT 4, 2000, 3000

DO
GOSUB Test_Photoresistors
GOSUB average_and_difference
GOSUB Navigate
LOOP

Test_Photoresistors:

HIGH 6
PAUSE 3
RCTIME 13,1,timeleft

HIGH 3
PAUSE 3
RCTIME 3,1,timeright

RETURN

average_and_difference:
average = timeRight + timeLeft / 2
difference = average / 6

RETURN

Navigate:
IF (timeLeft > timeright + difference) THEN
PULSOUT 13, 850
PULSOUT 12, 850
ELSEIF (timeLeft > timeleft + difference) THEN
PULSOUT 13, 650
PULSOUT 12, 650
ELSE
PULSOUT 13, 850
PULSOUT 12, 650
ENDIF

PAUSE 10

RETURN

emmali55 · 2008-12-20 16:57

If this helps... The pins I am using for photoreistors are 3 and 13

Mike Green · 2008-12-20 17:06

Replace "GOSUB Test_Photoresistors" with

DO
   GOSUB Test_Photoresistors
   IF timeRight > darkThreshold AND timeLeft > darkThreshold THEN
      NAP 6 ' Sleep for about one second, then repeat loop
   ELSE
      EXIT ' Continue with rest of program
   ENDIF
LOOP

You'll need to figure out the value of the constant "darkThreshold" by experimentation
using a small program that just calls Test_Photoresistors and displays the results using
DEBUG.

emmali55 · 2008-12-20 19:01

Thank you. I am working with it. It didn't work completely - kind of pulsed side to side. I also tried using the "Flashlight Controlled Boe-Bot" program. I can then just set the light levels as I need.··I·am getting somewhere - it pulses forward instead·or driving reg. speed forward.·I am still playing with the light levels. When I measured them, I got the following:
LEFT
Bright: 32
Med Shadow: 52
High Shadow: 380
Dark:0

RIGHT
Bright: 20
Med. Shadow: 28
High Shadow: 230
Dark: 0

When using your sleep code, to indicate the darkThreshold, I write --> darkThreshold CON lightlevel? And lightlevel being the Dark, High Shadow, or Med. shadow, right? I must leave now, but will play with the differences next time.

Let me know if I'm on the right track. Thanks again.

Post Edited (emmali55) : 12/20/2008 7:10:54 PM GMT

Help with christmas project! - photoresistors

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