Arduino controlling an RC car

This is a pet project I've been playing around with in my head for sometime now and I've finally taken the leap and started it.

My aim is to convert a cheap RC car into a robot chassis controlled by Arduino so I can easily experiment with robotics.

My original plan was to fake the the reciever's signal and run the motors through the provided PCB board in the car but it was so tightly packed and crappily wired I abandoned that idea, cutting wires and starting from scrtach.

I bought two RC cars together coming to about 15 dollars. I've only opened one so far- I've taken off the plastic body and opened up the body. I cut out the PCB and am attempting to figure out how to run the car's motors with Arduino. Plugging the motor directly into 5 volts causes the USB port to go on and off on Windows XP (I'm assuming it's tripping the USB protection which means I'm running too much current through arduino). On 3 volts it does this on the initial get-go and then when i stop the motor by hand, which once again makes sense.

I switched over to a Texas Instruments SN754410NE H bridge chip and thanks to this tutorial: http://itp.nyu.edu/physcomp/Labs/DCMotorControl I was able to get everything wired up. I decided to call it a night when the included battery pack's wire broke cause of the car's crappy soldering.

If I can get motors to run decently this weekend I think I can have proximity sensors installed next weekend with some basic behavior algorithms. So far the project is a success. I'll post more later.

Huzzah! After getting the h bridge to work thanks to that handy tutorial I mentioned I have the main drive motors running. Unfortunately I can feel the H bridge getting hot during its use - especially when I apply torque to the motors and run them at a much lower speed. They are drawing too many amps and are heating up the h bridge. I have to see if what I can do about that. If you have any suggestions PLEASE fire them my way, I've never dealt with heatsinks for a chip like that or h bridges in general before this.

Now I believe that the front portion of the car consists of a servo that turns both of the front wheels. I'm wondering if I even need to run an h-bridge to that as its a much lower gauge wire. I'm heading out for most of the night now but will continue work tonight and see if I can get that servo running. Then after I have both running on the bread board it is time ti resolder wires to make it all work as one complete portable package...

Hmm...My little brother drove his remote control car in to the pool so I might try the same thing. :D

Cant help with the motor problems sorry.

I plan on using a heat sink - I know where I can get one now.

Much to my surprise the steering of the car wasn't handled by a servo but a motor with a physical limit on how much it can turn. They had some kind of spring system in there that would return the wheels to their normal straight position when power wasn't applied to the motors.

That makes my job easier, especially considering that this motor is MUCH smaller and is pulling MUCH less amps - I can run it directly off of Arduino.

Cheater - keep me posted on how you do with the remote control car. I kind of wish I got a tank drive remote control car, so I hope you're working with that.

I'm debating if I should include a potentiometer on the bot to determine the amount its turning - if the spring system works it should theoretically always go to the middle, but it means the robot would never know how much its turning save a full left or full right. At the same time we're talking crazy geometry to determine turning position from variable turning on this kind of drive. Maybe down the road I'll add it, but for now I think I'll go the lazy route.

I'm going shopping tomorrow morning for ultrasonic sensors and a bumper switch or two (and basic stamps for future projects). If anyone knows of a cheap one that has 3 inch to a foot range drop me a note.

Cheater - keep me posted on how you do with the remote control car. I kind of wish I got a tank drive remote control car, so I hope you’re working with that.

Nah its a 4wd look alike one. Tank drive would be even cooler.

Runs off a 6v battery which makes live easier for me. :slight_smile:

Alright well robot's chassis is put together and now I just have to resolder some wires and then plug them into a solderless breadboard and place THAT on top of the robot. I've been shopping for cheap ultrasonic sensors and much to my dismay they don't seem to exist. I did find another forum that highly recommended the 8-10 dollar IR Sharp Rangefinder instead and it does seem to fit what I need -I can get two for under the cost for a half decent ultrasonic rangefinder. I do get less range, but at the same time this robot needs to only know about close objects, NOT far away objects. As an added bonus the sensor has a 4 inch minimum range, which is more suitable for me.

Have you considered using an electronic speed control (esc) for driving the motors? You could use pwm to handle speed..

Did someone ask for cheap ultrasonic sensors? :slight_smile:

http://www.futurlec.com/Ultrasonic_Sensors.shtml

12m range, you get 2 for $3.90.
Sounds like its overkill for you but the price is right and who knows? You may find a use for the extra range.

Also there is a waterproof variety for anyone wanting to do it on a R/C boat. :wink:

Wow, sweet. Cheater to the rescue.

Now will I have to build the circuit with these? hmmm I think I'll order these AND the infrared sensor and compare them - these are so cheap that I can afford both.

Just an FYI - I'm getting two of those ultrasonic sets plus an infrared sensor from here: http://www.robotshop.ca/home/products/robot-parts/sensors/contact-sensors/sharp-gp2y0d340k-ir-sensor.html