Found this RC rock crawler missing battery cover and remote at our local flea market. For only $2 thought it would be a good start for a bot. Will use the arduino that I already have for this I think.
Disassembly was straight forward, 4 screws on truck shell 8 screws on board cover and all is exposed.
This really turned out to be a find. Have recently ordered the new Start Here kit from Picaxe ouch$! In fact found this the same day. So for to 2 dollars I got 4 wheels, 2 brushed drive motors, brushed steering motor, 9V AA battery box, multi position power switch, and of course a nice chassie! Switch is set up for 3 channel RF operation so I could have switchable modes.
Tested motors, all 3 work. Was a bit surprized at how fast wheels turned on the 9V+ since it was called Rock Crawler. Will have to slow them down. Not sure yet if i'll drop the voltage to them or use PWM. Thought this would be a nice project to tied me over while I wait for the new picaxe Start Here kit to arive, use some of the stuff I have collected over the years and did nothing with, corse when I dug everything out, no motor shield or l293's which I am sure I had. Back to waiting on postman or in my case postwomen.
1/11/13
Made some progress yesterday. Crawler now has Arduino mounted on board. The electronics cover not only covered the electronics but holds the shock towers in place and provides the mounts for the body. I cut out the top of cover and 1 side in order to reassemble the chassie while still having access to Arduino and shield(s). Made a battery cover out of an old plastic case. Drilled out the fake roolbar and driving lights and mounted 5mm clear leds in them which I now can turn on and off with serial read.Still need to clean up my dremel cuts a bit but generally pleased with the overal progress with project.
1/13/13
Still unable to find a box of parts I know I have somewhere, ran to local Radio Shack and picked up a few things. Turning on leds with serial commands thru a USB cable was cool, well at least for my first time programing a microcontroller. But who wants a bot with an umbilical cord. Lights are now trigered by an LDR on A0 of Arduino and moved the output from D12 to D13 since it is already attached to an onboard led anyway. This is still on breadboard. Sitting here in the dark turning them off with a laser pointer. Body is now sporting a Krylon Fusion black satin finish. I had went to Wal-Mart to get a couple of cans of Testers paint and model glue. I don't do a lot of toy shopping and have not done a model in a decade or two but was surprised no completly shocked by the fact that they carried NOTHING! Didn't model cars used to be popular? Anyway... Oh and crawler bot now has a name. 2-of-4 walked in while I was re-assembling the body, we both are big Supernatural fans. To make a long story short she pointed out that I was working on the bot like Dean works on the Impala so crawler bot is now called Baby.
My motor control shield arived yesterday. Board from what I have learned from Googling (God bless Google) is an Adafruit clone. Thats the trouble I have ording off Ebay, seldom do I get any documentation with the parts I order (cause I'm cheep!). It is a nice board, solves a few isssues but causes a few as well. One of the parts I did find here was a sensor shield. Original idea was to stack the boards Arduino then motor shield then sensor shield. On the sensor shield inputs plug into the sides horizontally while outputs come off the top vertically. However, the motor shield does not accept a top board which puts the sensor shield in the middle of the sandwich eliminating my plan to attach the leds to top of board with female header cables.
The arrival of the motor shield means its time to decide what Baby should do. Think the best approach to this can be taken from the Star Trek the Motion Picture combined with Night Rider. Yes I do watch to much TV. Baby.s original wiring had both front and back drive motors running at the same time (always in 4 wheel drive).In addition to navigating on her own I think Baby should decide if she needs to be in 4 wheel drive or if 2 wheel would be enough. should be a nice challange for me. Time to start playing with the Adafruit motor sketch!
Baby lights off
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Baby lights on
1/14/13
After a bit more cutting on the cover I was able to fit sensor shield and motor shield on top of Adruino. Ordered pcb female header strips. The plan is to use them as stilts for motor shield to give better access to top pins of sensor shield. Still need to create a small board for LDR, 4.7K resistor, and and female header and mount LDR on body.
After some study of Arduino and Adafruit sites I was able to make Baby move. First with the Adafruit test sketch, then adapted it to control Baby via serial, and finally a small sketch that makes her go forward about a foot stop and reverse back to starting point. At this point only working with rear motor. Will probably test front and steering motors today. Running rear motor at a little over half speed showed postitive results with the idea of having Baby select 2 or 4 wheel drive. Rear motor moved her nice at a speed of 200 but was easily stopped in her tracks by a Directv remote control. I believe that the front motor can be triggered by a wheel encoder. If Baby is in forward or reverse and no movement in front wheel is detected front motor will fire matching speed and direction. Still waiting for sensors to show up . Need to start figuring out how to post some video. Think its also time to set some goals for Baby.
1/15/13
Mounted LDR to the truck bed. Since this sensor basically was just to componets I soldered and used heat shrink instead of using some perf board as I had originally planned. Although I the motor test seem fine Baby does not seem to have the power I thought she might after the original test of motors straight to batteries. I found a deal on 2 9.6v Nimh with charger but I have a feeling thats not the answer. The l293d's on the motor shield are getting a bit warm. Comparing the shield to original receiver board, the H-bridge transisters seem large in comparison but it was driving both front and rear motors together where I want to have the option of 2 or 4 wheel drive. Have a feeling I will be dumping the motor shield for a custom built h-bridge circuit. Going to try to cross reference the transisters today if I can get a number off of them. If any of my fellow LMRtions have any thoughts on this PLEASE chime in! Still have not received ultrasonic sensors yet.
GOALS
Baby should: Avoid objects, Choose her own direction when path is blocked, Decide if she needs 2 or 4 wheel drive, show change in direction and drive mode by triggering off road lights (depending on info received from LDR), turning, braking (stop) and reverse lights.
Baby can: Turn on and off driving lights