Ard-e: The robot with an Arduino as a brain

Step 6 Making Ard-e see, or at least go towards the brightest light

To make Ard-e have the sense of sight all you need is a few light sensors. I bought a pack of cadmium sulfide photocells from RadioShack for like 3 dollars. A lot of night lights have these that you can steal and the little outside solar lights are possible sources of these photocells too. I didn't have any of these laying around so I bit the bullet and bought them.

So these photocells change their resistance from around 10K to 100K ohms. I made up a little excel spreadsheet to figure out the possible values it would output if i hooked it up as a voltage divider. I got around 30K as providing the greatest difference from high resistance to low. I found some 39K resistors and figured they would work fine.

I just stuck them into the breadboard bent them forward and started testing out programs to make it seek out the brightest light. I ended up writing a program that reads the value from both sensors and if they are different by 8 it turns towards the one that is reading a higher value of light hitting it. I also used the 9V battery between the two sensors to block some of the light from spilling over and affecting the readings of the second photocell when Ard-e was turned one way.

Here is a video of Ard-e following the light from a flashlight that I was shining at him then veering off and going towards the light coming from the door. The quality of the video is really bad because the readings of the sensors get all screwy if alot of background light is present.

Now on to making Ard-e smell and hear.

Comments

[Chowmix12]

where's the actual code for the light seeking behavior?

[imadami]

I forgot to post the code for it and it was written on my old laptop... I did it two different ways. The first way was with two light sensors mounted on the left and right sides and pointing forward. I then programmed it to spin the side that had a higher reading faster. The other way that I did it was to mount a single light sensor in the middle of A-rde on a servo and have the servo turn to the left right and middle and measure the light at these three points. Whichever was the brightest it would drive towards, stop and then make another measurement. I never really got good light seeking behavior...

[Chowmix12]

Also, try making adjustable eyes. Use solid core wires soldered onto the two LDR pins and then twist the wires together. there bendy yet they hold their shape. i found that the best way to get them to work is pointing them upwards, bent slightly away from each other...

[Chowmix12]

i tried the first method with the cds cells connected to analog pins 1 and 2. the analog pins had 10k ohm resitors going to ground and the other end of the cds cell went to +5v. I'll PM the code for what i used, I got excellent behavior, very accurate. BTW, i used a l298hn chip instead of the l239d, because i was able to sample it. You should change the code for the l239d, and I dont mind if you post it on the I'ble for others to use.