Step 3Adding the brains
An old Dell C610 laptop I had lying around was dis-membered and the system board, memory and processor saved for the robot.
An old satellite set-top box served as the case for the project and mounted pretty easily to the top of the truck. I then mounted the system board and Sabertooth controller inside, along with a 12V 7AH SLA battery (slung under the casing), DC-DC converter to power the laptop from 12V and a failsafe.
The failsafe is a small 433Mhz key fob transmitter to cut the power to the motors if the robot should decide to make a break for freedom. It's a simple RC switch bought from Ebay very cheaply and used to toggle power to the Sabertooth.
I also added a small 12v fusebox and wired it all up with some cable from an old PC PSU.
My 8 year old webcam was rubbish so I went out and bought a Logitech 9000 PRO, which is very good and came on a tilting base which started me thinking that I could control it from the laptop via a servo to tilt the camera as the robot adjusted its distance from an object.
I used an SSC-32 servo controller from Lynxmotion to drive the servo and connected the controller to the PC via a USB to serial converter (I had already used up the laptops COM1 serial port for the motor controller)
The Dell laptop only has one USB port so I added a small hub to allow the USB to Serial module and the USB webcam to connect at the same time. With hindsight, I would have surfed Ebay for a Laptop system board that had USB 2 instead of 1.1, but it was all I had and works well for now.
The COM1 to Sabertooth cable needs to have a Serial to TTL converter fitted, you can find these on Ebay for under $10 or make your own as I did. This converts the RS232 levels to a lower 5v level suitable for the speed controller inputs.
I also added a chunky power on/off switch and soldered a remote pushbutton switch to the power button of the laptop. (Could have just drilled a hole in the case and used a prodder). A small 12V fan was added to the case to help cool down the laptop system board which isn't used to running without a case to direct the airflow.
The laptop had a Wifi card to enable me to remote control the robot from another laptop for making adjustments, etc without having to hook up a keyboard/mouse/monitor to the robot.
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