Design Philosophy
The Linux PC Robot is designed around a core principle: use what is available, cheap, or free. The target budget is $500 or less, achieved by reusing old desktop PC hardware, scrounging surplus electronics, and leveraging the vast ecosystem of Linux drivers and open-source code.
Rather than specialized embedded controllers, the LPCR uses a full x86 desktop computer as its brain — giving it a real operating system, real filesystem, real networking, and the ability to run any Linux application without recompiling or cross-compiling.
Core Components
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Desktop PC (ATX Form Factor) A retired Pentium-class desktop computer provides the CPU, RAM, storage, and expansion slots. An ATX motherboard was chosen for its wide availability, low cost (often free), and extensive Linux driver support. The PC runs a standard Linux distribution.
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ATX Power Supply A standard ATX power supply converts wall power to the regulated +12 V, +5 V, and +3.3 V rails required by the motherboard and peripherals. The 12 V rail also powers the motor drive electronics.
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Velleman K8000 I²C Interface Board The Velleman K8000 is a PC-based I²C bus controller that plugs into the parallel port. It provides 8 channels of 8-bit digital-to-analog and analog-to-digital conversion, plus digital I/O. The robot uses the DAC outputs to send signed drive commands to the H-bridge motor amplifier. Linux support is provided via the
i2c-parportkernel module. -
Custom H-Bridge Motor Amplifier A −5 V to +5 V dual H-bridge power amplifier (custom built) accepts the analog drive signal from the K8000 DAC and drives each motor proportionally forward or backward. Built from discrete components roughly 15 years before the project was documented, it exemplifies the project's ethos of using what is on hand.
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DC Servo Motors (pair) Two permanent-magnet DC motors provide differential-drive locomotion. Unlike stepper motors, DC servo motors are well-suited for continuous high-torque operation. Velocity and position are tracked via rotary encoders attached to each motor shaft.
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PS/2 Ball Mouse (converted to Dual Wheel Encoder) A surplus PS/2 ball mouse is disassembled and its internal encoder wheels are removed and mounted directly to the rear of each drive motor. The mouse PCB connects to the robot PC via PS/2 port. Linux reads the X- and Y-axis movement data as wheel encoder ticks, providing the feedback required by the PID motor controller. See the conversion guide for details.
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Drive Wheels and Caster Two large drive wheels (one per motor) provide traction. A rear passive caster allows the robot to turn freely. The differential-drive configuration means steering is accomplished by varying the relative speed of the two drive motors — no steering servo required.
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Custom Chassis / Frame A sturdy platform large enough to carry the ATX motherboard, power supply, and peripheral electronics. The frame was constructed from available materials and designed to keep the center of mass low and stable.
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Ethernet Network Interface A standard 10/100 Ethernet NIC in the PC allows network-based remote control and monitoring. A remote workstation running the joysender client can stream joystick commands to the robot over the local network. See Ethernet Cable for wiring details.
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Linux Operating System A standard Linux distribution (any x86-compatible distro) runs on the robot PC. The kernel's I²C subsystem, PS/2 input layer, and network stack are all leveraged without modification. Custom robot control software runs as normal Linux processes.
Approximate Cost Breakdown
The $500 target is achievable, and often beaten significantly, by sourcing used or surplus hardware. The table below reflects typical costs at time of build; many components may be free if scrounged from old equipment.
| Component | Approx. Cost | Source |
|---|---|---|
| Desktop PC (ATX) | $0 – $50 | Surplus / donation |
| ATX Power Supply | $0 – $20 | Surplus |
| Velleman K8000 Board | $40 – $70 | Velleman kit |
| DC Motors (pair) | $20 – $80 | Surplus / hobby shop |
| PS/2 Mouse (encoder) | $0 – $5 | Junk drawer |
| H-Bridge Amplifier | $20 – $60 | Custom / kit |
| Wheels, Caster, Hardware | $20 – $50 | Hardware store |
| Chassis Materials | $30 – $80 | Hardware store |
| Miscellaneous Wire / Connectors | $10 – $30 | Electronics supplier |
| Total (estimated) | $140 – $445 |