This build guide is intended to be an easy to use guide of how to build a MOPED care based on Raspberry Pi. Note that MOPED car is a research lab platform and it has a very complex electronics and software setup compared to a standard RC car. However the intended usage is completely different since the MOPED platform is a smaller version of the electrical architecture of future cars.
|1||M1||Model car chassis including servo||Turnigy SCT 2WD 1/10 Brushless Short Course Truck (ARR)||HobbyKing||9249000001|
|1||E1||Speed controller||Hobbyking X-Car 45A Brushless Car ESC (sensored/sensorless)||HobbyKing||9164000009|
|1||E2||Sensored brushless motor||Turnigy TrackStar 17.5T Sensored Brushless Motor 2270KV||HobbyKing||9192000029|
|1||B1||Rechargable battery||ZIPPY Flightmax 4000mAh 2S1P 30C hardcase pack||HobbyKing||Z40002S1P-30|
|3||E3,E4,E5||Raspberry Pi model B||RASPBERRY-PI – RPI-B-512-CASED||Farnell||2217158|
|3||E6,E7,E8||SDHC memory 4GB||SAMSUNG – RASPBERRY-PI / PROG-4GB-SDCARD||Farnell||2113756|
|1||E9||5V power supply||TURNIGY 8-15A UBEC for Lipoly||HobbyKing||TR-UBEC15|
|2||E10,E11||Reflective sensor wheelspeed||OPTEK TECHNOLOGY – OPB715Z – OPTO SWITCH, REFLECTIVE||Farnell||85414090|
|1||E12||Ultrasonic sensor||Ultrasonic Module HC-SR04 Arduino||HobbyKing||387000005|
|1||E13||9DOF IMU Acc/Gyro/Mag sensor||MPU-9150EVB||DigKey||1428-1010-ND|
|1||E14||Optionally (not tested): Ethernet Switch||DLINK DES-105||Dustin||5010620335|
|1||E15||WiFi Dongle||ELEMENT14 – WIPI – DONGLE, WIFI, USB, FOR RASPBERRY PI||Farnell||2133900|
|1||E17||Servo||(Part of M1 if ordernumber above is used)|
|Resistors||3x 2.2Kohm, 270ohm, 560ohm|
|3||H1,H2,H3||Optionally (not tested): Ethernet cable||DELTACO UTP CAT.6 UNSHIELDED RJ45 0.3M||Dustin||5010379761|
|3||H4,H5,H6||Micro USB harness||PRO SIGNAL – HK-US10/1 – LEAD, USB A MALE-MICRO B MALE, 1M||Farnell||2085464|
|3||CAN boards||See separate description|
|1||Wires Female-Female||Arduino Female-Female 3 x 40P 200mm Wire Jumper Cable||HobbyKing||438000073|
|1||Wires Male-Female||Arduino Male-Female 3 x 40P 200mm Wire Jumper Cable||HobbyKing||438000072|
|Headers 2,54mm spacing|
|PROTOTYPE BOARD, 100X160||Farnell||1201477|
|Charger||Turnigy Accucel-6 50W 6A Balancer/Charger||HobbyKing||ACC6|
|Programming Card||Hobby King HKSS programming card for HK 150A ESC||HobbyKing||HKSS-prog|
Start with an empty chassis.
The original motor is not suitable for low speed. Exchange the motor and speed controller to the one in the part list which has lower KV and is sensored.
- Disassemble the motor by first removing the motor cover.
- Under the motor cover loosen the hex screws holding the motor
- Loosen the small hex screw on the motor pinion and remove the pinion.
- Mount the pinion on the new motor
- Fasten the motor with the hex screws from the old motor. Adjust the freeplay between pinon and the big gear so there is some small play in between the pinion and the gear.
Connect speed controller and motor
Now it’s time to solder the wires from the speed controller to the motor. Check carefully the order of wires through the markings om the speed controller and the motor. Usually they are A, B and C.
Route the wires through the chassis before soldering. Also ad about 15mm shrinkage tube on each wire. Then connect the black sensor cable between the speed controller and the motor, routed similar to the power cables.
Battery power harness to speed controller
Cut the power wires to the speed controller to be able to solder the wires to the BEC. Also ad the battery sensor wire and voltage divider as shown in the picture below. Cover the soldering with 20mm long shrinkage tube. Use a 270ohm and a 560ohm resistor.
Mount the BEC on top of the battery plate with adhesive velcro tape, and the speed controller and its decoupling capacitors on the chassis rear firewall in front of the motor.
Mount 5 strips of reflective aluminum tape inside right front wheel and right rear wheel.
On right rear wheel, mount the reflective sensor with some dual sided scotch and some plastic coated single wire or a cable tie.
Solder 2,54mm single wire header connectors. On the white wire ad a xxx kohm resistor.
Servo and Speed controller board
To be able to connect speed controller and servo signaling and power a small distribution board is needed.
5V rail power distribution board
Several items need 5V powerdistribution from the BEC. See the pictures below.
Raspberry Pi power distribution cords (3pcs)
Cut micro-USB harness to suitable length for connecting the three Raspberry Pi:s. Typical these harness has read, black, white and green wiring inside. Black and red are ground respective 5V supply. Now solder 2,54 mm single wire headers to the black and the red wires. See the pictures below. Cover with shrinkage tubes.
Ultrasonic sensor board
To mount the ultrasonic sensor build a small breadboard as shown in the pictures below. The breadboard is mounted in the front of the chassis, just behind the protection bar. The trig signal (white wire on the picture) needs a 2,2 kohm resistor in series.
To be able to measure battery voltage there is need for an A/D converter board.
The A/D converter is connected to the SPI port on the SCU. See the connection table.
Preparing Raspberry Pi boards
During development it’s convenient to have possibility for manual reset of the raspberry Pi:s. To enable reset – solder a 2 pin header on the raspberry Pi board before putting the board into the lower half of the plastic case.
Mount the three Raspberry Pi:s by adding velcro fastners as shown in the pictures below.
Solder a header to the IMU board. Mount the IMU board with a screw in the front right pre drilled hole in the chassis bottom plate.
If CAN communication is to be used (this is the setup that is currently supported by the MOPED software), mount one CAN board on each Raspberry Pi by just putting them on the P1 connector. Connect the boards by simple wires, and put a jumper on one of the end nodes.
Optionally, if Ethernet is to be used (this is a promising approach but needs further software development), the Ethernet switch can be mounted on underside of the chassis. The switch has to be able to be supplied by 5V. Connect RJ45 cables in between the switch and the Raspberry Pi:s.
Now connect wires as described in the connection table to the Raspberry Pi:s. See the high res picture below about the final result.