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AUTONOMOUSE HEROBOT T   Last month, we described the three separate PC board assemblies that make up the Autonomouse. This month, you have to assemble these to form a chassis, mount the two motor/ gearbox assemblies, fit the wheels and complete the wiring. Part 2: By JOHN CLARKE T HE MOTOR/GEARBOXES are mounted on the copper side of board 3, as shown in Fig.10. Each unit is located with two 6mm tapped spacers near the drive shaft and two 9mm spacers at the motor end. Two mounting plates (20 x 35mm) cut from PC board or similar material are used to clamp the motor ends of the drives in place with 9mm long M3 screws. The standoffs are secured to the front of the PC board with M3 x 6mm screws. Note that some holes are close to adjacent PC tracks and you should use insulat­ ing washers under any screw or spacer which could cause a short between tracks. Rear panel Cut a piece of double-sided PC board 114 x 69mm and posi­tion it at right angles along the back edge of board 1, adjacent to the 2200µF capac64  Silicon Chip itor. It should protrude by about 1mm below board 1’s edge so the two edges can be soldered together. The right angle assembly should then be braced with a strip of 35mm long 0.75mm sheet brass, soldered to both board edges, as shown in one of the photos. Wheels & castor Making the wheels requires a little ingenuity. You could use wheels from a toy or make them from turned wood. We made ours by cutting the cheeks off two 200g Multicore solder reels. Each wheel was made by clamping two cheeks together with a 30mm alu­ minium hub on each side. The resulting wheels were 64mm in dia­meter, to give sufficient ground clearance for the robot. To attach the wheels to the drive shafts, we drilled a hole in the centre of the hubs which were slightly too small for the 15mm long tapped spacers which were then pressed into the hubs using a vice. The tapped spacers were then soldered to the gear­ box drive shafts. While we went to the trouble of making our own trailing castor, it turns out that you can buy a 30mm castor from hardware stores. You will need to make up the castor mounting brack­et for it though. This consists of a 40 x 60mm piece of single-sided PC board and two 40 x 40mm right-angle triangular pieces of PC board attached as shown in Fig.11. You will need to drill four holes in the main piece to mount the castor. The three pieces can be soldered together and the castor mounted on it but the assembly is not soldered to the rear panel of the robot just yet. Attach 15mm spacers to the front of board 3, the top of board 2 and top Fig.10: this diagram shows how the battery carrier sits above board 2 and how the motor drives are clamped to the copper side of board 3 using two mounting plates cut from PC board material – see text. October 1999  65 This is what the chassis looks like prior to fitting board 2 into position. Note how the motors are attached to board 3 which sits at the front of the unit, between the two large driving wheels. of board 1 using M3 x 6mm screws. Now secure the LED1 edge of board 3 to the transistor end of board 1 using a couple of short lengths of tinned copper wire soldered to the copper side of both boards. The soldering should be done to allow the wire to bend as a hinge joint. Mind you, you cannot bend it often otherwise the wires will break. The next job is to cut out the battery mounting plate. This measures 75 x 110mm and can be made from plastic or metal, etc. Drill holes in the corners to suit the stand­offs on board 1. Wiring it up This under-chassis view shows how three wire loops are fitted to the leading edge of board 1. The looped ends of these are soldered to the bottom of board 3 which has to be pushed against board 1 (the boards here are shown separated). 66  Silicon Chip Wire up the robot as shown in the diagram of Fig.12. Make sure that the various interconnecting wires are long enough to pass under the battery mounting plate which mounts on top of the spacers on board 1. You will need to drill holes in the rear panel for the switch and flashing LED. The LED mounts on the rear panel within the castor mounting bracket in a 5mm bezel. Solder two 9mm tapped brass spacers to the sides of the triangular bracket to support the red acrylic. Place the battery platform in position and attach it with four M3 x 6mm screws. Board 2 goes on the top of the assembly so far. So solder board 2 to the vertical edge of board 3 and to the rear panel, at the corners. Just tack-solder the boards at the corners. If you apply a lot of solder it will be difficult to disassemble the robot if you have to do any troubleshooting. The two wheels for the robot can be permanently soldered in place after the drive-shafts have been cut to length. Make sure that there is sufficient clearance for the wheels before cutting. The shaft ends are then soldered to the brass spacers in the wheel hubs. Now that the wheels are in position, you can solder the castor bracket to the rear panel. Make sure that the robot will be level when sitting on its wheels and castor. Bend IRD1 and IRD2 so that they face toward the outside corners and adjust IRLED1 and IRLED3 to the same angle. IRLED1 & IRLED3 should have short lengths of black plastic tubing over them to prevent the light from the sides being received. Testing Attach the battery packs with switch S1 off, then wind VR3 & VR4 (on the underside of the robot) fully clock­ wise. This will prevent the motors from running for the time being. Now switch on the power. The LED chaser at the front of the robot should be running from top to bottom and the rear LED should be flashing. If not, switch off power and check your wiring. Next, rotate VR2, on top of board 2, fully clockwise. Now place your hand about 60mm away from the IRLED3 and IRD2 pair and slowly adjust VR1 until the circular chaser starts up. Move your hand further away and adjust VR1 again to start the chaser. If the front chaser goes backward during these tests, you will need to take your hand away and wait for this reversing Fig.11: the castor bracket is made using single-sided PC board material, while double-sided PC board material is used for the rear panel. You can attach the castor either by using four screws and nuts or by gluing it. The two battery holders sit on an elevated plastic shelf attached to board 1. Power comes from eight AA alkaline cells. October 1999  67 Fig.12: this diagram shows how the three PC boards are wired togeth­er. Make sure you leave the wires long enough to pass under the battery carrier on board 1. action to stop before you can readjust VR1. You should be able to get a range of about 100mm although wheth­er that much is really necessary is debatable. Any sensitivity adjustments should now be done with VR2. Turning VR2 anticlock­wise will reduce the sensitivity. Adjust trimpots VR3 & VR4 to start the motors running. Adjust them to 68  Silicon Chip run at the same speed. Note that the wheels may be operating in the wrong direction in which case you simply swap the motor leads. Check that the robot runs on the floor and will turn away from obstructions. Adjust the speed to give smooth running. You will find that the robot runs best on smooth flooring and will tend to stall on carpet. Adjust the sensitivity for best re- sults. Low sensitivity to obstacles gives best results when the robot is running down a hallway. Note that the robot may not respond well to obstacles which are very dark or highly textured, such as cushions. This is because the infrared light is absorbed rather than reflected back to the robot sensors. Finally, place the red acrylic on the robot. The 60 x 90mm piece is for ELECTRONIC COMPONENTS & ACCESSORIES •  RESELLER FOR MAJOR KIT RETAILERS •  PROTOTYPING EQUIPMENT •  CB RADIO SALES AND ACCESSORIES •  FULL ON-SITE SERVICE AND REPAIR FACILITIES •  LARGE RANGE OF Ph (03) 9723 3860 Fax (03) 9725 9443 Come In & See Our New Store M W OR A EL D IL C ER O M E ELECTRONIC DISPOSALS (COME IN AND BROWSE) Truscott’s ELECTRONIC WORLD Pty Ltd ACN 069 935 397 27 The Mall, South Croydon, Vic 3136 email: truscott<at>acepia.net.au www.electronicworld.aus.as We made our own trailing castor but you can buy a 30mm castor from hardware stores. You will need to make up the castor mounting bracket for it, though. P.C.B. Makers ! If you need: •  P.C.B. High Speed Drill •  P.C.B. Guillotine •  P.C.B. Material – Negative or Positive acting •  Light Box – Single or Double Sided – Large or Small •  Etch Tank – Bubble or Circulating – Large or Small •  U.V. Sensitive film for Negatives •  Electronic Components and •  •  This photo shows how the motor ends of the drives are clamped to board 3 sing standoffs and two pieces of PC board material. the front, the 60 x 140mm piece is for the top and the 60 x 59 piece is for the tail. These are secured with M3 x 6mm screws secured into the standoffs through holes in the acrylic. Your Autonomouse can now be let loose, to wander about at will. Have SC fun! Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 •  ALL MAJOR CREDIT CARDS ACCEPTED October 1999  69