8   Foot Pedals

To get realistic action from the airplane or race car steering wheels (see chapters 2 and 6) you need to use foot pedals with them. But the need for foot pedals goes beyond making games more enjoyable. Several of the most important aspects of flying and driving involve the coordination of hand and foot movements. You can't use the power of the computer to learn to fly or drive until you can practice these essential coordination skills.

Fig.8-1. Sketch      These skills are critical in dangerous situations, such as landing a light plane in strong crosswinds or recovering from a skid on an icy bridge. With the steering wheels, foot pedals, and appropriate software, you can practice vital responses in a simulated but realistic environment. You can learn to anticipate and prevent accidents and gain the confidence you need to pass licensing tests.
     At present there are no commercial programs that use both steering wheel game controls and foot pedals. As this kind of hardware becomes available, commercial programs will certainly be modified to take advantage of this new feature. Meanwhile, you can write your own. If you can come up with even a modest program incorporating foot pedals you could undoubtedly get it published as an article in a magazine. The steering wheel/foot pedal combinations add such realism to flight and traffic simulations that we are certain software development will proceed at a rapid pace.
     The program we used to test the foot pedal prototypes was International Grand Prix by Richard Orban, from Riverbank Software, Inc. This program uses one paddle for the race car steering wheel and one pushbutton for the accelerator/brake. When this program is used with the race car steering wheel (chapter 6), the wheel controls the steering and the horn button controls acceleration and braking. This is a vast improvement over a conventional paddle in terms of feel and realistic action, but we all know that you don't brake an automobile by honking the horn.
     The prototype foot pedals were originally designed with two pots and no pushbuttons. To use a foot pedal with the International Grand Prix program we added a simple microswitch and a second cable and plug (see figure 8-1). Now the car accelerates when you move the foot pedal forward and brakes when you move it back. This is one step closer to real driving.

CONSTRUCTION
This is the easiest project to build in the entire book. It is a good exercise for the home or school woodshop, and the materials are inexpensive and readily obtainable. All the wood parts are 1/2-inch fir plywood except the heel rest, which is hardwood scrap. You can complete this project using only hand tools, but a table or radial arm saw will speed your work.
     Figure 8-2 shows side and back views of a completed foot pedal. The left and right units are identical, so remember to make enough parts for two units. Figure 8-3 gives you details of the separate parts and a top view of both the base and the foot rest.
     The eight pivot supports (figure 8-3) require careful attention. Two are simple pieces of plywood with 1/4-inch holes and a thumbtack at one end. The holes in two more supports are lined with brass bushings (1/4-inch ID). Another two supports have a 1/4-inch hole for the pot shaft and a drilled and tapped hole for a set screw. The last two supports are drilled out for the pot mounting bushing (usually 3/8-inch), tapped for a set screw, and notched for the spin prevention tab on the pot.

     After cutting out the plywood and hardwood pieces, round the corners and edges with a rasp or saber saw and sand all parts smooth. A Screw Mate drill bit is ideal for drilling the screw holes. Assemble the bases with 1-inch x #8 flathead screws and carpenter's glue. Then assemble the pots, upper pivot supports, and bolts. Attach the foot board to the upper pivot supports with the same size screws. Now take the entire unit apart and finish all wood parts with a bright-colored oil-based enamel.
     If you are installing the switch feature that lets the foot pedal act as one pushbutton for the International Grand Prix program, you will need a small sheet metal switch mount (see figure 8-2). Using hand shears, cut this out of galvanized steel, aluminum, or brass. Drill the top two holes in the metal to suit the switch and the bottom two for 1/2-inch x #6 panhead screws. For the prototypes we used a submini lever switch. The switch and the small mounting nuts and bolts were purchased at Radio Shack. Hold the sheet metal with vise grip pliers or in a bench vise while drilling so that it won't spin and cut your fingers. It is best to make the mount a little short, then move it up into position by shimming under it with thin cardboard, wood, metal, or plastic. The thumbtack shown in figure 8-2 should throw the switch when your foot is in a comfortable position, in the middle of the pedal's range of movement.
     The 1/4-inch bolts that form half the turning axis must have flat washers where the bolthead and nut touch the wood, and a plastic washer between the two wood parts. After final assembiy, lock the nut by applying Loctite, Super Glue, or fingernail polish to the threads.

ELECTRICAL WIRING
The foot pedal prototypes were wired for two separate game control arrangements. One arrangement has two foot pedals, each with one pot and no push button. The second arrangement has a single pushbutton on one foot pedal and was designed especially for playing International Grand Prix.
     Figure 8-4 is the schematic for the two-pedal version. The pots have short shafts (7/8-inch) and are mechanically rugged. They do not turn through a full 300 degrees, so their maximum values must be about four times the normal paddle pot values. If you use lower value pots, correction capacitors C1 and C2 will be needed. For the prototypes, 100K pots and correction caps were used. These caps were  placed on a small piece of printed circuit board and encased in a foam block at the place where the cables from the two pedals come together (see figure 8-1). If you use correction caps you will have to run the Correction Cap Calculation program from the software chapter to work out their values.

     The circuit for the single-pedal version is shown in figure 8-5. The common and normally-open terminals of the switch are utilized. The pull-down resistor R1 is placed in the plug/socket (figure 8-6). Note that all the pins on the socket pass straight through; no pins are cut or bent. This circuit simply adds an additional pushbutton 0 to whatever paddle is plugged into its socket.

     If you make up two foot pedals and add the switch circuit (figure 8-5) with its separate plug/socket to the foot pedal with pot 1, you will be ready to play any existing games and the future software that will use all the foot pedal pots. While you are waiting for the new software, you can plug the two-pedal version into the plug/socket of the switch version and play your favorite single-paddle games with your feet.

FINISHING UP
You don't want the foot pedals to slide under your feet, so the bottoms should be covered with something that grips the floor. If you will be placing them on wood or linoleum, cut and fit some pieces from an old inner tube on them. Cotton felt will grip a rug; for thicker carpets try incising shallow saw cuts across the width of the bottom. Extra weight helps, so you can add extra thicknesses of plywood to the baseboard or simply make the baseboard out of 3/4-inch stock.
     Perhaps you want the units to spring back to the open position when there's no pressure on them. You could do this by attaching rubber bands from the heel rest to the middle of the base, or by placing a urethane foam block under the middle of the footrest. There are probably many other different ways to spring-load these foot pedals. Use your imagination and experience to come up with a solution that suits your needs.

Parts List Foot Pedals

Number Required   Description of Part Suggested Supplier Total Cost 2 Pots, 100K, short shaft Jameco $6.00 1 Submini lever switch, #275-016 R.S.   1.30 15 ft. Telephone cable, #278-373 R.S.   1.70 2 16-pin DIP headers Jameco   1.40 2 16-pin sockets, wire wrap Jameco   1.40 1 Resistor, 1K, 1/4 watt R.S.     .10 2 sq.ft. Plywood, 1/2" fir Local   2.00 2 Bolts, 1/4" x 1-1/2" Local   1.00 4 Flat washers, 1/4" Local     .20 2 Nuts, 1/4" Local     .10 1 inch Brass tubing, 1/4" I.D. Hobby shop     .20 6 Flathead screws, 1" x #8 Local     .50 4 Set screws, 1/2" x #10 x 24 Local     .50 Misc. Nails, sandpaper, finish Local   2.10 ______ Approximate Cost   $19.00

Suppliers:     Jameco Electronics 1355 Shoreway Road Belmont, CA 94002 Minimum order $10.00 R.S.-Radio Shack See Yellow Pages All other parts were purchased at a local hardware store.