Gravitrax Power Starter (w/ Drop through & standard launcher)

This is a microbit based gravitrax Power starter. This initial version is similar to gravitrax's power starter. But unlike the gravitrax version this one can launch one or all balls at once. Or even code your own launching sequence.

There are additional design enhancements & accessories planned. This version is very usable and quite fun to play with I have ed it early. The design incorporates microbit which uses a kid friendly graphical coding environment. A sample code base is linked below. With two Microbits you can trigger the launcher remotely or through other input triggers. (Let you creativity decide)

List of Enhancements in the works
- Dome to attaché other gravitrax or printed parts for more balls storage
- Directional control tiles/blocks to select ball containers or direction to launch balls.
- Enhanced base to convert launcher to a fall through launcher. To direction control tile

Update 2924-08-22
Add a new base which turn the starter into a drop through launcher. The power launcher can now be placed on top any drop thought gravitrax part. The top & housing can be reused as is no additional assembly required. Just swap the tradition base for the drop through version.

Update 2024-06-21
The initial version is now complete. Added two version of the power starter dome. A Solid dome and decorated one with holes to make it easer to see through. Both version incorporate grip fins allowing gravitrax parts to be added to increase the number of balls stored. If you try to print the dome using transparent Petg be aware the gripfins will be too stiff.

Update 2024-06-14
Added a rail/track. Originally this was just a track I created for my self after I ran out of 72mm tracks. it was a quick and easy design but has the benefit of working really well with the launcher to stabilize the balls as they come out of the drop. If your choose to print it be carful to ensure the z-seam is not placed on the prongs. The wings used on traditional tracks help control and stabilize the balls. The wings have been extended through the full range of the track. Shout out to Chris (over at Masked Marble) for educating me on this fact ..

Additional instruction and assembly instructions are in progress . List of parts used are below. The approximate cost should be below $40 depending on options & controller. US and Eu parts will likely be significantly less. The electric starter is based a SG90 servo and Microbit control. A Pi pico or Adreno can also be used. The servo is mounted to the starter housing. A separate mount for the electronic will be ed later.

Microbit Project
Here are the Makecode links to the microbit transmitter and receiver projects.

Transmitter
https://makecode.microbit.org/S92932-97294-93783-55175

Reciever
https://makecode.microbit.org/S06921-49961-54217-69350

Note: The Responsiveness of the microbit will be influenced by text display. The default code displays Icons when a ball is launched. This results in on ball launched evert second. To improve responsiveness edit the receiver code and remove the icon display when one ball is launched.

Electronic Parts
The following are the parts I used, with a few as optional. Most of these I had on hand already. I suggest purchasing a pack of 5 or 10 sg90 servos. Future extension will ad additional control tiles.

• Microbit v2
• kitronik robotic board . You can use a simpler break outboard. or connect directly to the micro bit. (src code will need to adjusted appropriately) https://www.pishop.ca/product/kitronik-compact-16-servo-driver-board-for-the-bbc-micro-bit/
• sg90 servo
• Acrylic case & second micro bit (optional) https://kitronik.co.uk/products/56102-kitronik-mi-pro-protector-case-for-the-bbc-micro-bit-v1-v2
• Portable microbit battery accessories- may not have been visible but in the case an extension board battery back was used. (optional) https://kitronik.co.uk/collections/accessories-for-the-bbc-micro-bit/products/5610-v2-kitronik-mi-power-board-for-the-bbc-microbit-v2
• 6v AA / AAA battery holder- you can get away with 3v one too. Depending on the breakout board chosen

Assembly
Starter Housing and Servo
To align the arm and mount the servo you will need to run a few test to determine the direction and range of motion. These instruction will be base on setting things up for 90 degrees. The exact position may vary depending on make of your servo.

Servo position Alignment

• Plug in the servo with the sticker facing left and top up
• Instruct the servo to go to 90 degrees
• Add Ball Gate to the servo facing right aligned to 90 degrees
• Move the servo between 110 to 80 degrees to . 90 to 110 should move forward or away from you. And 90 to 80 should move towards you
• if your movement is opposite, flip the servo other way around or use minus/negative 90 in the code
• Screw the arm onto the servo
• Slide servo and arm into the housing with the arm between the gap
• Screw the servo into the mount. The servos ledge should rest flat on the mount

Testing the rang of motion
The exact angle that will drop a ball through or block may vary based on how the servo has been mounted. Initial values of 90 to drop ball and 100 to block are a good place to start. Update the code with the new values.

• Set the angle to 90 degrees and test if the ball will drop -If the ball is stuck, decrees the agnel by 1 to 2 degrees until the ball falls freely. If you hear a buzzing from the servo you have hit a chassis.
• Set the angle to 100 degree and test if the ball will not drop.
• If the ball continues to drop, increase the angle 1-2 degrees until the ball is captured.
• In the event your range of motion is blocked by the housing you may have position the servo too far over to one side. remount the servo. And repeat.

Servo Alignment code
To test the alignment and motion of the servo will require custom code to control the motion. Easiest approach is to move the servo with the two buttons and display the angel. It very simple code required. If you have challenges writing the microbit code to control the servos motion leave a comment below and I can provide a sample to work with.

Complete Assembly
- Insert the Base insert into the base. Some force may be required.
- Place the starter housing on to base. The house and the base can be secured by pressing near the ramp.

Parts are printed in PLA with .4 Nozzle. All parts can be printed on the bed facing up with no s.

Brims should not be required but if you're have difficult with StarterHousing or BallGate files a Brim may help.

The grip fins on top of the dome will be a bit tight at first. Insert my printed 1x spacer to loosen them at first.

The StarterHousing uses custom built in to the top of the Dome and servo mounts. The servo mount s can be easily broken away needle nose plier.

The interior of the of the housing is a dome shape. The can be broken free by pressing through the hole at the top. It will be a bit stubborn at first and may need coaxing with pliers. (Unfortunately the neck of the is quit thin due to spacing and found it easier to just break it then use it as leverage. )