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car-assembly.md
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NXP Cup Car - Complete Assembly Guide

← Back to Main | ← Shield Assembly

Assembly Steps Overview

  1. Chassis Preparation
  2. Mounting Motors
  3. Installing HEX Adapters
  4. Mounting Wheels
  5. Installing Ball Caster
  6. Mounting Spacers
  7. Mounting FRDM Board
  8. Connecting Shield
  9. Connecting Motors
  10. Mounting Line Sensors
  11. Connecting Ribbon Cable
  12. Installing Battery
  13. Connecting Battery
  14. Final Checks
  15. First Power-On Test

Before You Begin

Required Components

  • Assembled NXPCUP-Shield (from Shield Assembly Guide)
  • FRDM-MCXN947 development board
  • 3D printed chassis or base plate
  • 2x DC motors (25GA-370)
  • 2x Wheels (65mm)
  • 2x HEX adapters
  • 1x Ball caster
  • Line sensor array
  • Ribbon cable
  • 16x M3 screws (6mm length)
  • 2x M3 x 10mm spacers
  • 4x M3 x 20mm spacers
  • LiPo battery 7.4V 2200mAh with XT60 connector

Required Tools

  • Phillips screwdriver (for M3 screws)
  • Pliers
  • Multimeter
  • Cable ties/zip ties

Safety Precautions

  • ⚠️ Battery Safety:
    • Never connect battery with reversed polarity
    • Never short circuit battery terminals
    • Keep battery away from metal objects
    • Charge only with appropriate LiPo charger
    • Never leave charging battery unattended
  • Mechanical Safety:
    • Ensure all screws are tight before operation
    • Keep fingers away from moving parts
    • Wear safety glasses when cutting or drilling

Step 1: Chassis Preparation

Instructions

  1. Inspect the chassis:
    • Check for any defects or rough edges
    • If 3D printed, remove any support material
    • Sand rough edges if necessary
  2. Identify mounting points:
    • Motor mounting holes (usually 4 holes per motor)
    • Ball caster mounting holes (usually 2 holes)
    • Board mounting holes (usually 4 holes)
    • Sensor mounting holes (usually 2-4 holes)
  3. Clean the chassis:
    • Remove any dust or debris
    • Ensure mounting surfaces are flat
  4. Organize hardware:
    • Separate screws by type
    • Have spacers ready
    • Keep small parts in containers

Quality Check

  • Chassis is clean and free of defects
  • All mounting holes are clear and accessible
  • Mounting surfaces are flat
  • All hardware is organized and ready

Step 2: Mounting Motors on Chassis

Instructions

  1. Identify motor positions:
    • Left motor position
    • Right motor position
    • Motors should be parallel to each other
  2. Position the first motor (left):
    • Align motor mounting holes with chassis holes
    • Motor shaft should point outward (toward wheel position)
    • Motor body should be inside the chassis
  3. Insert screws:
    • Use 2x M3 x 6mm screws per motor
    • Insert screws from the external side of chassis
    • Do not fully tighten yet
  4. Align the motor:
    • Ensure motor is perpendicular to chassis
    • Motor shaft should be parallel to ground
    • Adjust position if needed
  5. Tighten screws:
    • Tighten in a cross pattern (opposite corners)
    • Tighten evenly to avoid misalignment
    • Ensure motor is firmly mounted
  6. Repeat for second motor (right):
    • Same procedure as left motor
    • Ensure both motors are aligned parallel
  7. Verify motor alignment:
    • Both motor shafts should be at same height
    • Both shafts should be parallel
    • Rotate shafts by hand - should turn freely

Quality Check

  • Both motors are securely mounted (8 screws total)
  • Motors are parallel to each other
  • Motor shafts are at same height
  • Motor shafts rotate freely without binding
  • All screws are tight
  • Motors do not wobble

Note: Proper motor alignment is critical for straight driving!

Step 3: Installing HEX Adapters

Instructions

  1. Prepare HEX adapters:
    • Take the 2 HEX adapters
    • Identify the set screw on each adapter
    • Loosen the set screw (do not remove completely)
  2. Check motor shaft:
    • Most motors have a flat side on the shaft (D-shaft)
    • This flat side prevents the adapter from slipping
    • Clean the shaft if needed
  3. Install first adapter (left motor):
    • Slide the HEX adapter onto the motor shaft
    • Push it on as far as it will go
    • Align the set screw with the flat side of the shaft
  4. Tighten the set screw:
    • Tighten firmly but do not over-tighten
    • The adapter should not slip on the shaft
  5. Test the connection:
    • Try to rotate the adapter by hand
    • It should not slip on the motor shaft
    • The motor shaft should rotate with the adapter
  6. Repeat for second adapter (right motor):
    • Same procedure
  7. Verify both adapters:
    • Both should be pushed fully onto shafts
    • Both should be tight and not slip
    • Both should be at same distance from motor body

Quality Check

  • Both HEX adapters are installed
  • Adapters are pushed fully onto motor shafts
  • Set screws are aligned with flat side of shaft
  • Set screws are tight
  • Adapters do not slip when rotated by hand
  • Both adapters are at same position on shafts

⚠️ IMPORTANT: If adapters slip during operation, the wheels will not turn properly!

Step 4: Mounting Wheels

Instructions

  1. Prepare wheels:
    • Take the 2 wheels (65mm diameter)
    • Check that the hexagonal hole is clean
    • Remove any manufacturing debris
  2. Install first wheel (left):
    • Align the hexagonal hole in the wheel with the HEX adapter
    • Push the wheel onto the adapter
    • The wheel should slide on smoothly
    • Push until the wheel is fully seated
  3. Secure the wheel:
    • Most wheels have a set screw or retaining screw
    • Insert and tighten the screw
    • Ensure the wheel is firmly attached
  4. Test the wheel:
    • Rotate the wheel by hand
    • It should turn the motor shaft
    • No wobbling or play
  5. Repeat for second wheel (right):
    • Same procedure
  6. Check wheel alignment:
    • Both wheels should be parallel
    • Both wheels should be at same height
    • Spin each wheel - should rotate freely
    • No rubbing against chassis

Quality Check

  • Both wheels are installed
  • Wheels are fully seated on HEX adapters
  • Retaining screws are tight
  • Wheels are parallel to each other
  • Wheels rotate freely without wobbling
  • Wheels do not rub against chassis
  • Both wheels are at same height from ground

Note: Wheel alignment affects driving performance. Ensure they are parallel!

Step 5: Installing Ball Caster

Instructions

  1. Identify ball caster position:
    • Mounted at front of chassis
    • Should be centered left-to-right
    • Position determines weight distribution
  2. Position the ball caster:
    • Place ball caster on mounting surface
    • Align mounting holes with chassis holes
    • Ball should face downward
  3. Check height:
    • With wheels on ground, chassis should be level
    • Ball caster should just touch the ground
    • Adjust if chassis has multiple mounting positions
  4. Insert screws:
    • Use 2 x M3 x 6mm screws
    • Insert from bottom of chassis
  5. Tighten screws:
    • Tighten evenly
    • Ensure ball caster is firmly mounted
  6. Test the ball caster:
    • Ball should rotate freely in all directions
    • No binding or sticking
    • Should roll smoothly

Quality Check

  • Ball caster is mounted securely (2 screws)
  • Ball caster is centered on chassis
  • Ball rotates freely in all directions
  • Chassis is level when on wheels and ball caster
  • All screws are tight

Note: The ball caster provides the third point of support. Proper height is important for stability.

Step 6: Mounting Spacers for FRDM-MCXN947

Instructions

  1. Identify board mounting positions:
  • Chassis have 4 mounting holes for the development board
  • These holes match the FRDM-MCXN947 mounting holes
  1. Determine spacer configuration:
  • All positions: 4 x M3 x 20mm spacers
  • This provides proper height for the FRDM board mounting
  1. Install spacers (20mm):
  • Take 4x M3 x 20mm spacers
  • Position at all 4 mounting holes
  • Insert M3 x 6mm screw from bottom of chassis
  • Screw into the spacer from below
  • Tighten securely
  1. Verify spacer installation:
  • All 4 spacers should be perpendicular to chassis
  • Spacers should be firmly attached
  • No wobbling

Quality Check

  • 2x M3 x 20mm spacers installed at rear positions
  • 2x M3 x 10mm spacers installed at front positions
  • All spacers are perpendicular to chassis
  • All spacers are tight (4 screws from bottom)
  • Spacers do not wobble

Note: The different spacer heights create a slight tilt, which can help with sensor positioning.

Step 7: Mounting Spacers for Line Sensors

Instructions

  1. Identify sensor spacer mounting positions:
  • Chassis have 2 mounting holes for line sensor spacers
  • These holes are at the front of the chassis
  • Position should allow sensors to be centered and face downward
  1. Determine spacer configuration:
  • Standard configuration: 2x M3 x 10mm spacers
  • Spacers create proper height for sensor positioning
  • Sensors should be 3-5mm from ground when mounted
  1. Install sensor spacers:
  • Take 2x M3 x 10mm spacers
  • Position at sensor mounting holes on chassis
  • Insert M3 x 6mm screw from bottom of chassis
  • Screw into the spacer from below
  • Tighten securely
  1. Verify spacer installation:
  • All spacers should be perpendicular to chassis
  • Spacers should be at same height
  • Spacers should be firmly attached
  • No wobbling
  1. Check sensor mounting alignment:
  • Place line sensor array on spacers (without screwing)
  • Verify sensor height from ground (3-5mm optimal)
  • Ensure sensors will be parallel to ground
  • Adjust spacer length if needed

Quality Check

  • All sensor spacers installed (typically 2x M3 x 10mm)
  • All spacers are perpendicular to chassis
  • All spacers are at same height
  • All spacers are tight (screws from bottom)
  • Spacers do not wobble
  • Sensor height will be 3-5mm from ground when mounted

Note: Proper sensor height is critical for line detection. The 3-5mm distance provides optimal detection while preventing scraping on uneven surfaces.

Step 8: Installing Battery

Instructions

  1. Identify battery mounting location:
    • Battery mounts in center of chassis
    • Dedicated battery holder/support is provided
    • Should be accessible for removal/replacement
  2. Prepare battery mounting:
    • Locate the dedicated battery support in center of chassis
    • Prepare zip ties for securing battery
    • Ensure battery support is clean and free of debris
  3. Position the battery:
    • Place battery in the dedicated center support
    • XT60 connector should be accessible
    • Battery should be centered for weight distribution
    • Ensure battery is oriented correctly (check polarity markings)
  4. Secure the battery:
    • Thread zip tie(s) through battery support slots
    • Wrap zip tie around battery
    • Pull zip tie tight to secure battery firmly
    • Trim excess zip tie length
  5. Verify battery installation:
    • Battery should be firmly mounted in center support
    • Should not move when chassis is shaken
    • XT60 connector is accessible
    • Battery does not interfere with wheels or other components
    • Zip tie is tight and secure

Quality Check

  • Battery is mounted in center dedicated support
  • Battery is firmly secured with zip tie (shake test)
  • XT60 connector is accessible
  • Battery is centered for weight distribution
  • Battery does not interfere with wheels or components
  • Battery polarity markings are visible
  • Zip tie is tight and trimmed

⚠️ SAFETY: Ensure battery is very secure. A loose battery can cause damage or fire hazard!

Step 9: Mounting FRDM-MCXN947 Board

Instructions

  1. Prepare the FRDM-MCXN947 board:
    • Remove from anti-static packaging
    • Inspect for any damage
    • Identify the 4 mounting holes
  2. Position the board:
    • Align the board mounting holes with the spacers
    • USB connector should be accessible (usually toward rear or side)
    • Ensure correct orientation
  3. Place board on spacers:
    • Carefully lower the board onto the spacers
    • All 4 mounting holes should align
    • Do not force - if holes don't align, check spacer positions
  4. Secure the board:
    • Insert 4x M3 x 6mm screws through board holes
    • Screw into the top of each spacer
    • Tighten in a cross pattern (opposite corners)
    • Do not over-tighten (can crack the PCB)
  5. Verify board installation:
    • Board should be stable and level (or at designed angle)
    • No wobbling
    • USB connector is accessible
    • All mounting screws are snug

Quality Check

  • FRDM-MCXN947 board is mounted on spacers
  • All 4 mounting screws are installed and tight
  • Board is stable with no wobbling
  • USB connector is accessible
  • Board is at correct orientation
  • No stress on the PCB

⚠️ CAUTION: Do not over-tighten screws - this can crack the PCB!

Step 10: Connecting NXPCUP Shield

Instructions

  1. Prepare the shield:
    • Take the assembled NXPCUP-Shield
    • Inspect all header connectors
    • Ensure no bent pins
  2. Identify mating connectors:
    • Shield has female headers (J1, J2, J5, J6)
    • FRDM-MCXN947 has corresponding male headers
    • Check alignment before connecting
  3. Align the shield:
    • Hold shield above the FRDM board
    • Align all header connectors
    • Ensure correct orientation (usually marked on PCB)
  4. Connect the shield:
    • Lower the shield carefully
    • All header pins should start entering the sockets
    • Do not force! If pins don't align, lift and realign
  5. Press shield down:
    • Apply even pressure across the shield
    • Press down until shield is fully seated
    • All connectors should be fully mated
  6. Verify connection:
    • Shield should be parallel to FRDM board
    • No gaps between shield and board headers
    • No bent pins visible

Quality Check

  • Shield is properly aligned with FRDM board
  • All header connectors are fully mated
  • No bent pins
  • Shield is parallel to FRDM board
  • Shield is stable and does not wobble
  • All connectors (J1, J2, J5, J6) are connected

⚠️ IMPORTANT: Bent pins can cause malfunction or damage. Be very careful during this step!

Step 11: Mounting Line Sensors

Instructions

  1. Identify sensor mounting position:
    • Sensors mount at front of chassis (or rear, depending on design)
    • Should be centered left-to-right
    • Should face downward toward the track
  2. Prepare the sensor array:
    • Line sensor array typically has multiple IR sensors
    • Check that all sensors are clean
    • Identify mounting holes on sensor PCB
  3. Position the sensors:
    • Place sensor array on the spacers installed in Step 7
    • Sensors should point downward
    • Align mounting holes with spacer tops
    • Ensure sensors are perpendicular to driving direction
  4. Secure the sensors:
    • Use 2x M3 x 6mm screws
    • Insert screws through sensor PCB holes
    • Screw into the top of each spacer
    • Tighten evenly in a cross pattern
  5. Check sensor height:
    • Optimal distance: 3-5mm from ground to sensor face
    • Too close: may scrape on uneven surfaces
    • Too far: reduced sensitivity
    • Adjust spacer length if needed (return to Step 7)
  6. Verify sensor orientation:
    • Sensors should be parallel to ground
    • Sensors should be centered on chassis
    • All sensors should be at same height

Quality Check

  • Line sensors are mounted securely on spacers
  • Sensors are 3-5mm from ground
  • Sensors are parallel to ground
  • Sensors are centered on chassis
  • Sensors face downward
  • All mounting screws are tight
  • Sensors do not interfere with wheels or ball caster

Note: Sensor height is critical for line detection. Test on actual track and adjust if needed.

Step 12: Connecting Motors to Shield

Instructions

  1. Identify motor terminals:
    • Each motor has 2 wires (usually red and black, or both same color)
    • Left motor wires
    • Right motor wires
  2. Identify shield motor terminals:
    • J11: Motor 1 terminal (usually left motor)
    • J12: Motor 2 terminal (usually right motor)
    • Each terminal has 2 positions
  3. Prepare motor wires:
    • If motors don't have wires pre-attached, solder wires to motor terminals
    • Use appropriate gauge wire (typically 22-24 AWG)
    • Solder one wire to each motor terminal
    • Ensure good solder joints (shiny, not cold/dull)
    • If wires are too long, consider shortening (leave some slack)
    • Strip wire ends if needed (about 5mm)
    • Twist stranded wire ends to prevent fraying
  4. Connect left motor to J11:
    • Loosen both screws on J11 terminal
    • Insert one motor wire into first position
    • Insert other motor wire into second position
    • Tighten both screws firmly
    • Tug gently on wires to ensure secure connection
  5. Connect right motor to J12:
    • Same procedure as J11
    • Loosen screws, insert wires, tighten screws
  6. Cable management:
    • Route motor wires neatly
    • Avoid wires near wheels or moving parts
    • Use cable ties to secure wires to chassis
    • Leave some slack for movement/vibration

Quality Check

  • Wires are soldered securely to motor terminals
  • Solder joints are clean and shiny
  • Left motor connected to J11
  • Right motor connected to J12
  • All 4 terminal screws are tight
  • Wires are secure (gentle tug test)
  • Wires are routed away from wheels
  • Wires are secured with cable ties
  • Some slack in wires for vibration

Note: Motor polarity determines rotation direction. If a motor runs backward during testing, simply swap its two wires at the terminal.

Step 13: Connecting Ribbon Cable

Instructions

  1. Identify connectors:
    • Line sensor connector: Usually on sensor PCB
    • Shield connector J1: 2x10 pin header on shield
  2. Prepare ribbon cable:
    • Identify pin 1 on both ends (usually marked with red stripe or arrow)
    • Check cable length - should reach from sensors to shield
    • Ensure cable is not damaged
  3. Connect to line sensors:
    • Align ribbon cable connector with sensor connector
    • ⚠️ Match pin 1 markings! (Pin 1 is separated from the other pins in the socket)
    • Press connector firmly until fully seated
    • Some connectors have a latch - ensure it clicks
  4. Route the cable:
    • Route cable from sensors to shield
    • Avoid sharp bends
    • Keep cable away from wheels and moving parts
    • Leave some slack for vibration
  5. Connect to shield J1:
    • Align ribbon cable connector with J1 on shield
    • ⚠️ Match pin 1 markings!
    • Press connector firmly until fully seated
  6. Secure the cable:
    • Use cable ties to secure ribbon cable to chassis
    • Ensure cable cannot get caught in wheels
    • Do not over-tighten cable ties (can damage ribbon cable)

Quality Check

  • Ribbon cable connected to line sensors
  • Ribbon cable connected to shield J1
  • Pin 1 orientation is correct on both ends
  • Both connectors are fully seated
  • Cable is routed neatly
  • Cable is secured with cable ties
  • Cable has some slack
  • Cable cannot interfere with wheels or moving parts

⚠️ CRITICAL: Incorrect pin 1 orientation can damage the sensors or shield!

Step 13: Final Checks Before Power-On

Mechanical Checks

  • All screws are tight (motors, wheels, ball caster, boards, sensors)
  • Wheels rotate freely without rubbing
  • Ball caster rolls freely in all directions
  • No loose components
  • Chassis is stable

Electrical Checks

  • All connectors are fully seated:
    • Shield to FRDM board (J1, J2, J5, J6)
    • Motors to shield (J11, J12)
    • Line sensors ribbon cable (both ends)
    • Battery to shield (J10)
  • No visible short circuits or solder bridges
  • All wires are secured and routed properly
  • No wires near moving parts (wheels)

Component Orientation Checks

  • Shield is correctly oriented on FRDM board
  • LM339 ICs have correct orientation (notch alignment)
  • Diode D1 has correct polarity
  • XT60 connector has correct polarity
  • Ribbon cable pin 1 is correct on both ends

Safety Checks

  • Battery is firmly secured
  • Switch S1 is in OFF position
  • Work area is clear of metal objects
  • Fire extinguisher nearby (recommended for LiPo batteries)
  • No damaged wires or components

Documentation

  • Take photos of completed assembly (top, bottom, sides)
  • Note any modifications or issues
  • Record battery voltage before first use

Step 15: First Power-On Test

Pre-Power Checks

  1. Final visual inspection:

    • Look for any obvious problems
    • Check all connections one more time
    • Ensure nothing is loose

  2. Prepare for test:

    • Place car on a non-conductive surface
    • Elevate car so wheels don't touch surface (use a stand or blocks)
    • Have multimeter ready
    • Be ready to quickly turn off power if needed

Power-On Procedure

⚠️ IMPORTANT: Keep your hand on switch S1 to quickly turn off if needed!

  1. Turn on power:

    • Switch S1 to ON position
    • Observe immediately

  2. Check for problems (first 5 seconds):

    • No smoke → If smoke appears, turn OFF immediately!
    • No burning smell → If smell detected, turn OFF immediately!
    • No excessive heat → Touch components gently, turn OFF if very hot
    • No sparks → Turn OFF if sparks appear
    • No unusual sounds → Turn OFF if buzzing or popping sounds

  3. Check LEDs (if no problems detected):

    • Power LED on shield is ON
    • Power LED on FRDM-MCXN947 is ON
    • Any status LEDs show expected state

  4. Measure voltages with multimeter:

    • Battery voltage at XT60: ~7.4V (or current charge level)
    • 5V rail on shield: 5.0V ±0.25V
    • 3.3V on FRDM board: 3.3V ±0.15V

  5. Check components:

    • Shield components are not excessively hot
    • DC-DC converter (U1) is slightly warm (normal)
    • Motor drivers (U2, U3) are cool or slightly warm
    • FRDM board is cool

  6. Turn off power:

    • Switch S1 to OFF position
    • Wait 10 seconds
    • Check components for any residual heat

If Everything is OK

Congratulations! Your NXP Cup car hardware is assembled and powered correctly!

Quality Check

  • Power-on successful with no issues
  • All LEDs functioning
  • Voltage measurements correct
  • No excessive heat
  • No smoke or unusual smells

Assembly Complete! ✓

Your NXP Cup car is now fully assembled and ready for programming!

Safety Reminders

LiPo Battery Safety

  • ⚠️ Never short circuit battery terminals
  • ⚠️ Never puncture or damage battery
  • ⚠️ Never charge unattended
  • ⚠️ Never exceed 4.2V per cell when charging
  • ⚠️ Always use LiPo-specific charger
  • ⚠️ Always store in fireproof bag
  • ⚠️ Always dispose of damaged batteries properly

Operational Safety

  • ⚠️ Keep fingers away from moving wheels
  • ⚠️ Ensure car cannot fall off table during testing
  • ⚠️ Test in safe area away from obstacles
  • ⚠️ Have emergency stop method ready
  • ⚠️ Wear safety glasses during assembly/testing

Electrical Safety

  • ⚠️ Always turn off power before making connections
  • ⚠️ Never work on powered circuits
  • ⚠️ Check polarity before connecting battery
  • ⚠️ Disconnect battery when not in use
  • ⚠️ Keep liquids away from electronics

Next Steps:

← Shield Assembly | ← Back to Main

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