Psycho Scooter Scramble is a blind-driving electric wheelchair game. It consists of two riders, strapped into electric wheelchairs, and two blindfolded pilots, who remotely control the wheelchairs from the sidelines based on information given over headset by their driver.
The basic mechanic is simple: players must drive across the court to get a ball from a stand, then drive back across to put the ball in a
hoop. This action is repeated until all four balls have been scored or the timer runs out.
Since there is an inevitable disconnect between the pilots’ steering and their teammates’ intentions, wheelchairs zigzag across the court at high speeds, colliding with each other, ball stands, the scoreboard, and most everything else; all the while, taking full advantage of the custom steel bumpers.
Psycho Scooter Scramble was created for the Creation Challenge. Team Instructables includes Amanda Ghassaei, Audrey Love, Eric Wilhelm, Gabriella Levine, Greg Johnson, Jake Rogers, Jessy Ellenberger, Matthew Dalton, Noah Weinstein, and Randy Sarafan.
Step 1: Go Get Stuff
(x2) electric wheelchair
(x1) 1"x1"x10' square steel stock
(x1) 2.5"x.175"x20' steel flat bars
(x1) Wireless SD Shield
(x1) Xbee S1
(x1) PC Board
(X12) male header pins
(x4) 2K resistors
(x4) 1K resistors
(x4) 5.1K resistors
(x1) 9V battery connector
(x1) 9V battery
(x1) 22 AWG stranded wire
(x1) wireless headset
(x1) Large-ish sealable plastic food container
(x1) assorted zip ties
(x1) Wireless SD Shield
(x1) 9V battery connector
(x1) 9V battery
(x1) 4' x 8' sheet 3/4"wood
(x2) floor flanges
(x2) 1/2" threaded metal pipe
(x2) 24" x 24" acrylic sheet
(x1) 4' x 8' x 3/4" plywood sheet
(x2) 48" threaded pipe
(x2) threaded nipples
(x2) elbow joints
(x2) small whiteboards
(x4) 36 x 24" 1/8" black acrylic sheet
(x2) 36" x 24" x 1/8" orange acrylic sheet (for lettering)
(x2) 12" 7-segment display
(x1) Annoying buzzer
(x1) Light-up stop hand
(x1) Red arcade button
(x1) green arcade button
(x1) PC Board
(x1) 5V relay
(x1) 5V / 120V 10A solid state relay
(x2) giant 7 seg display
(x2 darlington uln2803
(x1) 8' x 4' x 3/4" plywood board
(x2) Basketball nets
(x1) Staple gun
(x8) Kick balls
(x2) 4' x 8' plywood sheet
(x2) 4x4 wood beam
(x4) 2x4 across
(x1) 20' thin metal rod
(x2) referee shirts
(x1) 1 yard of bright orange fabric
(x1) 3' dowel rods
**Cart materials are for ideal conditions. Parts may vary depending on the electric wheelchair you are confronted with.
Step 2: About Electric Wheelchairs
You can get working electric wheelchairs on Craigslist for much cheaper than you may ever think possible. We got ours for about $150 each. We heard one of the ones we bought typically retails for about $11,000. That is pretty hefty savings.
Some of the wheelchairs that we bought were sold as-is. They did not turn on. We later learned that "as-is" is typically code for "needs new batteries." We solved this by purchasing some 12V deep-cycle forklift batteries for $30 a piece. These turned out to be gel cell batteries that could be positioned on any side. They worked like a charm.
Once we had all 4 electric wheelchairs up and running, much silliness ensued. After we got that out of our system, we then proceeded to fully mod them.
Step 3: Fit New Batteries
When necessary we cut away non-structural bits to give the batteries more room and/or build new platforms or enclosures to hold the batteries in place. When necessary, we also needed to extend the battery wires to reach the battery terminals.
While this was happening, we were also charging all of the batteries.
Step 4: Build Armor Frames
Tools needed for this step:
Angle Grinder with metal sanding disc
Grinder and Cut-off wheel
For all four chairs, we used two 1"x1"x20' steel square stock to build out the frames. We decided that five support struts would be sufficient to weld continuous steel flat bar to. Each chair was a little different, and needed to be modified differently. Once the main frame supports were welded to the frame, we could weld the flat bar to the supports. This part was a bit tricky, and took a bit of teamwork.
Each bumper was designed to float 3 inches from the ground, and we created a wood jig to guide the flat bar around the steel struts as they were welded and bent in to place. We worked as a team, because the flat bar is long and wobbly. We used one 2.5"x.175"x20' per cart - tacking on the edge of the flat bar as it hovered on a 3" jig from the ground, and then bent and tacked around the frame.
Step 5: Hack the Wheelchair
For the communication, we used one arduino to receive the information from two joysticks and transmit that data via xbee radio. We strapped a receiving xbee/arduino onto each wheelchair and used this data to control the wheelchair.
We wanted to maintain as much of the original controls as possible. To do this we wired into the controller's joystick. The joysticks on these wheelchairs are understandably more advanced and accurate than a normal gaming joystick. They work off of a hall effect principle and have four sensors embedded in them. Here is the joystick's datasheet which explains the pinout, seen in the image above.
We cut the 8 stranded ribbon cable connecting the joystick to the controller on the wheelchair. On the transmitting end, we wired up the joystick following the pinout diagram so Arduino received two analog inputs (forward / backwards, left / right).
The wheelchairs will not start if it does not sense that the joystick is connected and in a neutral position. To do this, we needed to mimic the joystick signals with an Arduino. It turned out this was rather tricky to do for the position switches. We ended up wiring the control board to a voltage divider, which we controlled using relays. The relays were wired in parallel with resistors in the voltage divider so that they shorted out the resistor when closed. Using two relays wired in this configuration, we could mimic 3 different joystick positions from the center junction of the voltage divider. These corresponded to the neutral position and two extreme positions on either side of neutral. This circuit was repeated twice: one for forward, neutral, back, and another for left, neutral, right.
This worked because we only wanted the wheelchair to move in one of four directions and did not care too much about the intermediary values. The wheelchair has some built-in functionality to prevent sudden stops and starts, so this was not a problem.
Here is the receive code:
Step 6: Build the Control Pedestal
Make a little plywood box underneath to hold the electronics. Paint in team colors and glue on laser cut acrylic lettering (optional).
Finally drill holes for joysticks.
Upload the following code to your Arduino (with Wireless Xbee shield):
Finally, the transmitting Arduino was connected to two joysticks. It monitored the signal from the two inputs of each joystick with its analog inputs. Then it compared these signals to a threshold value and sent out a piece of data accordingly.
Step 7: Make a Scoreboard
Screw flanges to the center of base struts, and the back of the board. Screw pipe components together (board flanges --> to nipples --> to elbows --> to long rods --> to floor struts).
Cut out your letters. They can be stuck on to decorative arc with carpet tape. Attach arc to top with struts and bolts.
The electronics on the scoreboard largely consist of two 12" common anode 7-segment displays, the illuminated stop hand, a buzzer, 2 arcade buttons, and an Arduino-based circuit.
The 7 seg displays were controlled by pins A0-A5 and D0-D7 of the Arduino via a Darlington 2803 (to source more current). Each seg of the giant 7-seg displays was made up of four parallel lines of 15 red LEDs in series. It runs off a 35V AC to DC power supply. Other than the special current and voltage considerations, the giant 7-seg is controlled like any other common anode 7 seg display.
Step 8: Hoops
We stapled the basketball net to the back of each hoop board with a staple gun.
Hoops should be painted in team colors.
Step 9: Ball Holders
Paint in team colors.
Step 10: Boundaries
We made wood-and-rope boundaries, and they didn't help at all. They're just a piece of 4x4 on a plywood base and an eye hook screwed in to hold a rope.
Do something better and more effective, because the wheelchairs will hit the boundaries on a regular basis.
Step 11: Blind Goggles
Step 12: Referee Flags
Sew a loop that fits snugly around your dowel rods, and then slip it onto the dowel to make your flag.
Step 13: Comm Units
We used vox-capable walkie talkies with headsets.
Each passenger-pilot pair needs a pair of headset walkie talkies on the same channel. The passenger's walkie-talkie can be zip tied to the frame of the wheelchair, and the headset should be put on under the safety gear.
Communication should be one-way: the pilot's headset should be a monitor, and the passenger should be transmitting at all times.
Set the passenger's vox to the highest sensitivity. Disable the pilot's vox by pressing PTT once after turning the walkie talkie on.
Step 14: Safety Equipment
Additional safety equipment may be necessary. Participant discretion is advised.
Step 15: How to Play
The court is ideally fenced in on all or most sides by chain link fence. The court may also be delineated by fence posts and rope, or plastic orange restraining fence. Lacking all of these, it can be defined by drawing it on the ground with chalk. Barring that, players can define imaginary boundaries using mutually agreed upon fixed landmarks (such as trees and rocks and things).
Before the game starts, the scooters are manually wheeled to the center of the court. The drivers put on colored shirts, appropriate safety gear, and their seatbelt. Taunting is encouraged before gameplay begins.
The game starts with both teams face to face in the middle of the court. The referee blows their whistle and presses the green button to start the game clock. Each player must then retrieve the ball of their team color, and then drive to the opposite end of the court to try to throw it through their color goal before time runs out. Each goal scored counts for one point, which is then marked on the scoreboard by the referee. When time runs out, the red hand will light up and buzzer sound. At this time, all gameplay stops. The driver and pilot switch roles for the game to start again.
After two full rounds, the team which successfully throws the most balls through the hoop is deemed the winner.
During gameplay the referee may blow their whistle to warn the pilot of inappropriate conduct, and/or wave their flag to warn the driver of inappropriate conduct. It is suggested the player stops whatever it is they were doing that warranted this warning. Should things get really out of control, the referee may choose to hit the red foul button on the scoreboard. This stops the clock and all gameplay must stop. The court is then reset, and both drivers must return to the center of the court before gameplay can resume.
If at any time the pilot takes off their blind goggles, the team is automatically disqualified from the match. Use of weapons will also result in automatic disqualification.
Throwing your ball at the blindfolded pilot of the other team is highly antisocial and discouraged. Knocking them out cold will definitely result in a foul and stop gameplay.
Grabbing the opposite team's goal and wearing it around your head like a necklace is also extremely antisocial and discouraged. This too may result in a foul and stop gameplay.
Step 16: Repair Damaged Wheelchairs
Also, the bumper is invariably going to get dented. This can easily be fixed by kicking or hammering back into shape.
Step 17: A Note on Referees
The referee is responsible for maintaining law and order, keeping everyone safe, calling fouls, stopping and starting gameplay, keeping score, freeing stuck carts, and excessively blowing their whistle.
As the last remaining voice of reason, it is recommended that you don't run over the referee. However, this is sometimes unavoidable.