• Schematic Part 1

    Lauri • 03/05/2025 at 14:03 • 0 comments

    I started with motor driver circuit. As the steering motor is so small and cannot handle too much current I needed to find a stepper driver with sense input. Second neccessary character is low voltage operation. 2.7V-15V is suitable for this project.

    Second circuit is about USB input for charging and programming

    To be on the safe side there needs to be a USB to serial converter: 

    For MCU I chose ESP32S2 MINI  as it has enough I/O for this project

    Power is handled by main switch 

    And a TP4056 is chosen for charger 

    3.3V linear regulator for ESP32

    And simple battery level measuring input

    Missing are some LEDs and buttons. To make some noise I chose this piezo buzzer. Porbably I should make some calckulations on the drive power for that. 

  • A battery or 3 batteries?

    Lauri • 02/21/2025 at 18:53 • 0 comments

    I started with an 18650 battery without any protection electronics, just for testing. It has worked fine so far. My initial idea was to buy an 18650 with a protection circuit or design it on the board myself. After some research, I found that not many toys use Li-ion chemistry, so I decided to explore alternative solutions as well.

    What does Brio use? According to this post, at least some of their trains use a 2000mAh 1.2V NiMH battery. That’s not as easy to use in my case, so I measured and found that I could use a 3S NiMH battery as a safer alternative to Li-ion. However, I also discovered that there are not many easy solutions for designing a 3S charger. This TI article suggests that a Li-ion charger could be used for 3S NiMH. If I were to use NiMH, I would buy Eneloop AAA batteries. The price for 3 Eneloop batteries would be between 9-12€.

    Instead of trying to find room for 3 AAA batteries, I decided to look for Li-ion batteries locally in a similar price range. I found that a CR123 or 16340 battery would be available, costing around 9€.

    The NL169 was locally available and has similar specs to what 3 AAA batteries would have:

    Specifications:

    • Capacity: 950mAh 3.6V (3.42Wh) (vs. Eneloop 800mAh)
    • Max Continuous Discharge: 2A (vs. Eneloop 2.4A)
    • Diameter: 16.6mm±0.2mm / 0.65"±0.01" (vs. Eneloop 3x 10mm)
    • Length: 34.1mm±0.3mm / 1.34"±0.01" (vs. Eneloop 45mm)
    • Weight: 20g / 0.71 oz (vs. Eneloop 3x 13g)

    Now that the NL169 has been chosen, I can start working on the PCB design.

  • First test on tracks

    Lauri • 02/13/2025 at 10:54 • 0 comments

    Even if there are a lot of wires and loose battery, it seems that it works quite well on tracks. 

    I tested the steering part after the video. There are some modifications to do, but it will steer to the other track on the intersection. 

    The control with one analog joystic is not that fun, I will do a better design for controls later. 

    Here is a video: 

  • First drive

    Lauri • 02/11/2025 at 13:20 • 0 comments

    Steering system consists of steppter motor and a pushrod that will guide front axle free movement to left or right. If stepper motor is in the middle then axle can steer freely.

    All the wheels have O-ring for the friction. Rear wheels are directly connected to the motor gearbox. Front wheels have a 1.6mm wolfram (TIG welder tungsten electrode) as an axle, that rotates freely in the slot. 

    Finally, ESP32, 2 motor drivers and a battery is connected and first drive on the floor is done. 

  • Prototyping starts

    Lauri • 02/05/2025 at 20:40 • 0 comments

    Fist components arrived. Managed to do some initial setup and testing for remote control with ESP-NOW.
    For the remote control transmitter I hooked up an analog joystick to the ESP32 S3 Zero.
    The receiver is also ESP32 S3 Zero.


    Drive motor is working, not sure is this particular motor best for the task. It is fast, but not so powerful at low speed. Finding N20 motor with correct speed, voltage, torque is challenge.
     
    Steering stepper is working also, but has overheating issue as I cannot limit the current for the motor with this simple dirver.

    Next steps:
    Design of the test enclosure to test out drive motor and steering motor on real track.