This is an extract from my web page at ... www.geocities.com/zs6bne/myrobotlawnmower.htm Name: MACH 2001 Robot Lawnmower Components used: I managed to purchase two identical second hand Nissan Skyline wiper motors and a 12 volt blower motor from a motor scrap yard dealer in Potchefstroom not too far from my home in Lichtenburg , Northwest Province , South Africa. The wheels are standard 170 mm diameter lawnmower wheels obtained from the local hardware store. Their traction is not all that good but they made a good start for the robot lawnmower project. The evolution of my robot lawnmower The various components evolved over time by trial and error , doing sketches here and there and somehow they all fitted together as though they were designed as such! The onboard computer I used an old 386DX40 small sized computer for the "brains" of the robot lawnmower. It's maybe a bit of an overkill but it was simply available and I enjoy controlling the outside world via the printer port. It is a cheap and easy method for computer control. As can be seen above , I cut the motherboard mounting area from an old desktop computer case for use as supporting hardware for the video / printer port card , the floppy disk controller card and also the 386 motherboard. The onboard power supply I used second hand YUASA Gel batteries which were replaced by new ones in computer UPS systems. Two 6 volt batteries were wired in parallel to supply sufficient power to the 386 PC via a silicon diode to drop the voltage down to approximately 5 volts required by the PC. No fancy voltage regulation at this stage but it must get the highest priority for the future. The third battery is a 12 volt battery used for the wiper motors , cutter motor and automotive switching relays shown below. I may even add a second 12 volt battery to power the cutter motor alone seeing this motor can draw currents in excess of 5 amps and over 20 amps on startup! The whole setup is not as efficient as one would like it to be , but this was to get something going with no unnecessary problems to get it done. No electronic H Bridges and speed control circuitry although I have plans to use an output of the printer port for a software controlled pulse width modulated signal for possible speed control when applying power to the wiper motors and possibly even the cutter motor too. The cutter itself will probably be in the form of a bush cutter's blade or edge trimmer. This still has to be experimented with. The I/O system All I/O control is done via the printer port (LPT1) of the onboard 386 PC. Inputs will be read from various sensors via the input interface module when the budget allows it. The input interface module is basically just a biasing network for the input lines on the printer port. The lines are biased to +5 volts via 1 to 10K resistors and can also provide a supply to the open collector sensor output circuitry. The manual computer command simulator When the PC is not running , I have a computer command simulator to switch the motors on , off , forward and reverse to give desired robot movements. This is simply a box of switches interfaced to the output control circuitry. Software development The software is written using Visual Basic for DOS which I found on the internet and it allows me to do event driven programming which is a little better than using languages like PASCAL or normal BASIC. I just have to plug in a standard IBM PC Keyboard and Mono screen. I use a removable 1.44 Mb floppy drive to boot the PC with DOS and load the program into memory. Thereafter I remove the floppy drive and the program continues normally running in the 2 Mb of onboard RAM. The cost of my robot: I thought it would be of interest to mention what my robot lawnmower cost to make it a reality and it is by no means complete. Chassis (Cover from an old electronics unit) Free Second hand Gel batteries Free Angle iron for mounting brackets Free 386DX40 Motherboard + 2 Mb RAM Free Video / LPT card and IDE controller card Free Additional hardware (Bolts and nuts) R 30-00 1.44 Mb Floppy drive Reusable Two second hand wiper motors R 300-00 One second hand fan motor R 100-00 Lawnmower wheels R 140-00 Castors (Had to buy 4 of) R 60-00 Automotive relays R 100-00 Electronic components and veroboard R 100-00 Two Infrared TX/RX kits (Awaiting arrival) R 111-00 TOTAL R 941-00 To compare internationally , South Africa's Rand is equivalent to approximately R 7-80 to the dollar. Contact information Email is most welcome. I would love to share ideas with other robotics enthusiasts. I know my robot is very primitive and still needs a lot of attention. The important thing to do in the near future is to replace the two balancing castors with a large third castor to assist with movement over grass. The small ones tend to get in the way. I can be contacted at the following two email addresses: edleighton@hotmail.com or at work at eddieleighton@nwk.co.za